Brain

Outline
Thesis: Unless the risks of usage of cell phones outweighs the benefits, we should educate people on how to manage their usage of cell phones or use a different mean of communication.

The Effects that Cell Phones have on Society

Introduction
In the United States of America, there are over one hundred million cell phone users. This number is growing at an astonishing rate of more than sixty thousand people per day. (Cellular Telephones) Thirty percent of all Americans have joined the mobile-phone revolution. A decade ago, cell phone usage in the United States was a rarity. (Raloff) The most common domestic appliance that Americans use every day is the cell phone, and we deserve the right to know the effects that this appliance is having on us. There are also many risks associated with cell phone usage. We must outweigh the risks and benefits for ourselves to decide if using cell phones is really worth it. Unless the risks of usage of cell phones outweighs the benefits, we should educate people on how to manage their usage of cell phones or use a different mean of communication. Cell Phones can be Distracting!

Cell phones can be a distracting nuisance in the busy life an American. People have been encouraged to carry on phone conversations in inappropriate situations. Many citizens complain that cell phones often interrupt church services and other activities that require silence or concentration. Cell phones frequently disrupt recreational and cultural functions, breaking down traditional lines between work and leisure. (Cellular Telephones) Many people complain that cell phones are invasive devices. Events such as weddings, funerals and live theatre productions are often interrupted when cell phone calls are received. Cell phones have made uninterrupted private or leisurely activities a rarity. Some citizens are also concerned that cell phones can cause car accidents by encouraging drivers to talk on the phone while behind the wheel.

Cell phone conversations can diminish the ability for a driver to identify hazards and avoid accidents. Benjamin King, a spokesperson for Highway Watch, a California-based highway safety organization in Los Angeles, says that carrying a conversation while driving is just as dangerous as driving drunk. “If the phone is on, you’re asking for trouble,” King says. “It’s the equivalent of having a couple of drinks before you start the car.” (Cellular Telephones) Cell Phones and the Weakening of Relationships

Would you really want to spend time with someone who does nothing but sit there looking at their phone, texting and getting on social media, or are you the person sitting there on their phone nonstop for hours on end each day? It’s sad that this is what people in our society encounter each and every day. Many people claim that cell phone usage irritates them. They claim that it detracts people from the quality of life in general. As cell phone usage increases with little restriction, some citizens are demanding limits on when and where phone conversations can take place. According to Jill Andresky Fraser, author of “White Collar Sweatshop (2001),” many parents feel obligated to spend less quality time with their children. (Cellar Telephones) Cell Phones can make you dumb!?

Do you use the recent “text-lingo” when texting your family and friends? Do you use shorter versions of words or even use letters to symbolize those words? Do you use “lol”, “jk”, “brb”, “gtg”, or “lmbo”? If you do, then you may have fallen prey to the latest “text-lingo.” People in other countries would be surprised to find out what those letters from earlier actually stand for. Why can’t people use proper grammar while texting? They don’t realize that it will only take about two more seconds of their time to spell the whole message out instead of shortening everything. Plus you wouldn’t lose brain cells! People are in such a rush that they have to shorten everything that they send in a text message, and this causes them to want to use this “text-lingo” all of the time, rather than correct grammar. If people would practice using correct grammar more often, they wouldn’t have as much trouble doing things such as writing a job resume and writing an essay. Can I die from using cell phones?

Will one phone call to your grandmother be the last phone call that you ever make, or will you get cancer from the radioactivity that cell phones emit? Many citizens have become concerned that cell phones can cause cancer. For many years, health experts have investigated claims that the radio waves emitted and received by cell phones could heat brain tissues, leading to genetic mutations that cause formation of cancerous and noncancerous tumors. (Cellular Telephones) Cell Phones generate electromagnetic fields that affect biological tissues and create diseases, putting millions of people at risk. EMFs are all around us in any object that has an electrical charge.

There are invisible lines of force that surround all wiring and electrical instruments. The strength of these fields varies from indoors to outdoors along with the individual’s surrounding environment, which changes from day to day. EMF waves from cell phones challenge the human body’s natural electrical frequency by continually penetrating the entire body and disrupting homeostasis within neural transmission. This increases the risk of harmful diseases. They also damage DNA and cause headaches, tumors, brain cancer, and loss of hearing. (Wimmer) Benefits of Cell Phone Usage

Increase in Public Safety
Cell phones are hailed as a boon to public safety. They provide citizens the ability to respond to emergencies regardless of their location. Cell phones are often used to alert authorities in the event of accidents or criminal activities. They have decreased the amount of time that it takes for emergency assistance to help citizens in distress. Each day more than one hundred thousand emergency calls are made using cell phones, according to the Cellular Telecommunications Industry Association. Cell phones can also be used to prevent crimes such as domestic abuse. Some organizations in the country have been funded to collect used cell phones, and give them to shelters for battered women. The phones have also been distributed to victims of spousal abuse, who can call 911 in the event of an emergency. Cell phones can also be used to ensure the safety of citizens in high risk occupations. Examples of these occupations are security guards and taxi drivers.

Many people also consider cell phones to be an excellent means for parents to watch over their children who are at school or with friends. These parents are concerned by high rates of crime among many young people and by recent outbreaks of violence on school campuses. They allow their children and young people to carry cell phones for personal protection. (Cellular Telephones) Cell Phones can be a fuel for Economic Growth

Cell phones have spurred economic growth through increased sales of telecommunications equipment, and by creating thousands of jobs. Some say that cell phones have increased productivity by allowing private companies to facilitate better communication and cooperation between employees. Sales for cell phones have generated vast amounts of revenue for companies that sell subscriptions to cellular network services. High demand for cell phones is also fueling growth in sectors such as advertising and electrical components manufacturing. Growth of the economy that is fueled by sales of cell phones will also be fueled for many years to come. Cell phones have also been credited with increasing worker productivity. Analysts say that cell phones have allowed employees to take work home and to continue working while in transit. That development has decreased the costs required to operate businesses and the amount of time that it takes to complete projects. (Cellular Telephones) Cell Phones can help maintain relationships

Many people have welcomed the proliferation of cell phones as a positive development. Cell phones are a convenient means of maintaining relationships, organizing social activities and conducting occupational activities. (Cellular Telephones) Cell phones have made it more convenient to communicate, work and live. They are put on the market to assist in our “quality of life,” and does a great job in doing so. (Wimmer) Cell phones can be used to talk to relatives or friends that live anywhere in the world. They can be used quickly organize any activity such as a birthday party, flag football game, or even a family dinner. Outweighing the Risks and Benefits

Health Risks and Benefits
EMF waves are all around us. They come from any appliance with an electrical charge. Too much exposure to these waves can be dangerous to humans. When a person puts a cell phone up to their ear to talk on the phone, EMF waves are being transmitted through their ear canal to their brain. The results from these studies can be very disturbing, but the truth is that we don’t know if they are actually true. According to The Food and Drug Administration’s chief of Radiation Biology Branch, “There is not significant new evidence in the past year that there is need for greater concern than already exists.” Many say that it will take several years for scientists to reach a consensus on how dangerous cell phones actually are to human health. (Cellular Telephones) Alan W. Preece of the University of Bristol in England did many studies on the effects of cell phones on human memory. He stated “I was looking for memory effects but didn’t find any.” There are many studies on the effects on cell phones but ask yourself “Is this really credible, or are we too early in the game to see these effects?” (Raloff) Cell phones can also cause cultured human blood vessel cells. They can make genes less active than usual and even increase blood vessel permeability in the brain. (Pickrell) Communication Risks and benefits

Though cell phones can be used to communicate in very positive ways that can also be used to do harmful things. For example, people can use cell phones to communicate with each other in a group of people who plan to rob a bank. If they did not have cell phones they could have more trouble communicating with each other to get everything together to rob the bank. Another example of people using cell phones to harm other people is through bullying. Most teenagers send text messages to their friends very frequently. Many times teenagers text their friends about the latest gossip. Often the latest gossip includes something negative about someone. If that negative thing gets back to the person that it was about, it can severely hurt their self-esteem. If people are getting made of through social media too much, they can have suicidal thoughts and may actually kill themselves.

There also positive means of communicating through cell phones. If someone has a relative that lives across the country, they can keep in touch with that person through cell phone use. If a woman has a husband who is overseas at war, they can use a cell phone to communicate with each other. There are many negative and positive things when communicating through cell phone use. Economic Risks and Benefits

The impact of cellular technology, along with devices such as portable computers played a direct role in fueling economic growth throughout the nineteen-nineties. (Cellular Telephones) Cell phones have spurred economic growth for many years. There are not many negative aspects of cell phones economically. One negative aspect is that it creates a great ordeal of competition between cell phone companies because cell phones are so popular. Another negative aspect would be that cell phones have decreased the sales in newspapers and magazine articles all over the country. Conclusion

From the moment that cell phones were invented and sold, people all over the world went crazy. There are so many benefits to cell phone use but there are also many risks. Some benefits include that they are a distraction, education threat, and can cause distractions, cancer, and other health risks. Some benefits include that it is a fuel for economic growth, maintains relationships, and can increase public safety. People use cell phones every day, and would be lost without them, but they need to do their research and assess the risks and benefits of cell phones. If people find that the risks outweigh the benefits, simple modifications such as turning off cell phones while driving, and keeping conversations to a minimum, may be the most effective means of fixing the problem of cell phone use addiction. These efforts could prove more effective to restore the peace of the pre-cell phone era. It’s sad that it may take years for people to learn how to use cell phones in a manner that is mature, safe, and acceptable to everyone.

Works Cited:
Kavoori, Anandam. “Mobile Communication and Society: A global perspective.” Journal of Broadcasting & Electronic Media. Mar. 2009: 161+. Academic OneFile. Web. 24 Oct. 2013. Pickrell, John. “Contradictory Studies Heat Up Radiation Question.” Science News 161.26 (2002): 404. General Science Full Text (H.W. Wilson). Web. 24 Oct. 2013. Raloff, Janet. “Researchers Probe Cell-Phone Effects.” Science News 157.7 (2000): 100. General Science Full Text (H.W. Wilson). Web. 24 Oct. 2013. Wimmer, Ronda. “Minimizing the long-term effects of EMFs from cell phone use.” Acupuncture Today Feb. 2008: 34+. Health Reference Center Academic. Web. 24 Oct. 2013. “Cellular Telephones.” Issues & Controversies On File: n. pag. Issues & Controversies. Facts On File News Services, 2 Mar. 2001. Web. 24 Oct. 2013.

What causes and effect human actions? Have you ever had moment where you had to ask yourself “why did I just do that?” or shocked by your own uncaring attitude? Human behavior is prejudiced by multiple diverse factors, some neural and some environmental. Various of these influences have developed over thousands of years of human history and civilization. Chemical progression in the brain that take places milliseconds before a given behavioral act happens.

To know human behavior, we must explore interest in the biology of the brain, philosophy and past. The saying goes that everything happens for a reason is a valid statement when it comes to grasping human behavior. Before a given behavior occurs the oldest parts of the human brain kick into gear. In a fatal moment occurrence, the brain processes sensory data based on its immediate environment. Different societies will condition us humans to behave in diverse ways.

The brain makes numerous split-second decisions before an aggressive behavior takes place. Two fragments of the brain control aggression which are the amygdala and the frontal cortex. The amygdala is located part of the brain, the cerebral cortex, and is the region connected with aggressive behavior and fear. This was discovered during a research that showed individuals photos that stimulate rage or fear to see in what way the brain would course the images.

The front cortex oversees regulating emotions including aggression and control impulsiveness. This was confirmed by the case pf Phineas Gage in 1848, while working on a construction site an iron rod punctured his skill and destroyed his frontal cortex. He survived the accident he was a totally changed man.

Childhood and adolescent experiences effect our behavioral development. As we’ve been told 85 percent of the brain is fully developed in the first two years of life. Now the remaining is essential for determining behavioral development. Teenage years is a critical time for brain development. The immature frontal cortex can negatively influence behavioral traits.

Its been proven that the frontal cortex doesn’t finish developing until we’re in our mid-20s, which would explain the spike in violent behavior seen in our childhood and young adults. As a child the brain can absorb information much faster than an adult. Studies show that 33 percent of adults who was involved in childhood abuse will cause the abuse to their kids.

Empathy and compassion aren’t as closely connected as everyone thought. The anterior cingulate cortex is activated when you perceive others pain. ACC is a region of the brain that’s allied to the frontal cortex and the amygdala. Its responsible for helping us learn to fear observable bad experiences.

The neurological connections indicate that empathy had more to do with self-preservation than with a desire to help other. Study shows empathy leads to the activation of the amygdala activation while compassion is led to the initiation of the frontal cortex. Many would say that human behavior is easily predicted but is a highly complex and multifaceted field.

Human behavior is linked to brain chemistry and the society in which we live. Whether its behaving aggressively or felling empathy toward other, different pars oh the brain is activated when we carry out these behavioral acts. Only by understanding how these how these behaviors come about can we accurately understand what it means to exist and function in a society.

Brain Death Determination When the brain has a lack of oxygen, even for a few minutes, it could lead to loss of brain functions such as a gradual loss level of consciousness or a complete loss of consciousness causing the person to slip into a coma. In the most profound cases, irreversible brain damage and death occurs. Oxygen deficiency can by caused by many things, such as; a brain injury, fall from height, traffic accidents, heart failure, stroke or some neurological disease. That may cause irreversible loss of the brain cells performance.

The medical term for insufficient oxygenation to the brain is referral Anglia. Historically, before recent technology the scientists defined death only when the heartbeat and breathing stopped. Afterward, the idea of brain death was announced in 1959 by French neurologists’ Moldable and Gluon. They determined this state as “beyond coma” (D*mice et al. , 2004). Then after around ten years, within the medical community the development of many types of equipment became available which aided in increasing the longevity of individuals with serious injuries to the brain.

Some examples of these devices are ventilators to maintain respiration and heart monitors. These innovations in medicine made the concept of brain death clearer by closely showing the relationship between the respirations or heartbeat and brain. These innovations in the medical field guided the Harvard Medical School Committee to clarify that idea in 1968 (Sass, 2014). After that, it was medically defined as permanent loss of all brain functions, including cerebrum and brain stem due to total death of brain neurons that is caused by decrease of blood flow and oxygenation into the brain (ibid).

This essay will discuss the main brain regions that have immediate cause of brain death and their functions, including the required tests of these regions, both clinical and confirmatory, for instance, the Electroencephalogram. The brain carries two major parts, cerebrum and brain stem. When they have any cause of damaged that might be a final result in brain death. Each one has primary roles in a person’s life, because they are responsible for the main operations in human survival, especially the regulation of cardiac and respiratory functions.

The cerebrum is the largest part of the brain and divided into two hemispheres (Fall & Bergman, 1998). There are main functions for he brain cerebrum without them no human can live. It is important to be concerned with functional specialization of different regions of the cerebrum to guide the treatment of the physician and assists them in making the right diagnosis. The cerebrum has a large primary sensory area, which is responsible for general sensation, for example, smell, vision, and hearing.

The motor area is responsible for controlling the skeletal muscles, and the association area of the cortex has operations similar to the sensory areas but more complicated such as behavior, communication and intellect (ibid). Secondly, the brain stem is located in the posterior division of the brain and connected to the spinal cord. Beside that it includes three significant parts; medulla obbligato, pens and mandarin. Each one controls principal performance and it is the pathway of sending and receiving sensory information signals from the body to the brain.

It has other important functions that have a major affect on a person such as regulation of the respiratory system, consciousness, alertness and awareness (Kiering & Barr, 2009). In general, both cerebrum and brain stem damage may end a arson’s life because they contain all the regulation centers for all of the most critical functions that are needed to sustain life. There are many criteria to diagnose brain death. Each country has their organization, but there are general rules and guidelines in determining brain death for patients worldwide.

There are important tools to consider when deciding whether the patient is dead or not, before the process of diagnosis of death by the criteria. The first tool is a person who is approaching the protocol of brain death qualified? For example, an ICC physician, an anesthesiologist, an internist, a neurosurgeon or a neuron physician are allowed and qualified to perform the tests because they have studied and trained to diagnose brain death, but a dermatologist or an ophthalmologist they have not done training on that.

Although, they need to know the state of the patient and must be in a coma with ventilator support and the cause of their comatose condition must be rolled out, for instance, Head trauma, Cardiovascular hemorrhage, cerebral Anglia or primary brain tumor. Next, the cause of brain damage must be clarified six hours before tarring brain functions evaluation. Finally, the patient should not be hypothermia and body temperature has to be above 34 C or 32 C in some countries protocol and the person should not be under sedatives, muscle relaxant, anticonvulsant… Etc Drugs for at least the previous five days. When these tools completed correctly the physician can start the diagnosis in following exam steps. The first clinical examination is to confirm that the patient is in a coma and to make sure a patient is not having any seizure activity in the brain. Furthermore, the physician needs to test he absence of motor response by painful stimulation for both hands and feet. It is required to do these evaluation exams on the standard method before starting the brain stem reflexes test because each exam depends on the previous one to give correct final result.

Once the physician has done from the previous evaluation he will start the brain stem reflexes tests, which called the first clinical examination. These are five different exams and begin with papillary response. The light stimulation to test the pupil response by bright beam of light on both eyes, for example, a pen alights. Also, corneal reflex is involuntary blinking and has to be tested via a wisp of cotton wool to touch the cornea. Thirdly, cool-cephalic reflex it does perform by moving the head to a different direction and monitor the retina changes during the head movements.

Fourthly, vestibule-ocular reflex this another test to activated eye movements by injecting both ears about 50 ml of ice-cold water or saline for adult, but children, less than 20 ml may be used. After all, upper and lower airways stimulation is produce either gagging or coughing. Furthermore, this exam’s purpose or provoke the pharynx and trachea. For instance, using catheter leads down to reach into the pharynx and the trachea (Saudi center of organ transplantation, 2009). Accordingly, all those brain stem tests should result an absent responses to declare brain stem death.

After finalization of the first examination, it’s recommended to not start the second clinical test before 6 hours from the time of first exam end for an adult and after 12 hours for children (above 1 year),24 hours for infants (above 60 days-I year) and 48 hours for neonate (7 days-60 days). Therefore to have enough mime to perform the confirmatory tests, such as Electroencephalogram (EGG) which is a machine that has 21 electrodes connected to the skull to cover all the brain regions and measures the electrical activity of the brain (ibid).

In fact, the EGG and other confirmatory tests are optional in some countries but it is often helpful for the physician to prove that the brain is permanently damaged by having more than one test that confirms his diagnosis and prognosis. The next clinical exam is apneas; it is done to indicate the failure of involuntary respiration. This exam has a specific rotator to perform it, such as an increase the inspired fraction of oxygen without changing the ventilation rate, disconnect the patient from the ventilator for 10 minutes and supply a continuous flow of humidified air.

These procedures are done to detect if there is any attempt for the patient to breathe (ibid). Another test that is sensitive in analyzing the circulation in the brain is transitional Doppler (ETC) this examination detects the velocity of the blood that’s circulating in the blood vessels supplying oxygen-rich blood to the brain. It uses ultrasonic waves that are focused onto a beam that is directed at different depths and angles by an experienced operator. The technologist uses sites on the skull where the bone is relatively thin and relatively close to the major vessels whose blood flow velocities are critical.

One major vessel that supplies the brain is the Middle Cerebral Artery (MAC). When the blood flow circulation is compromised to the extent that survivability is not possible the ETC shows reverberating waveforms as the blood ceases to flow in it’s normal direction and instead is ineffectually regurgitating back and forth without flow in espouse to the heart contraction. Later there are systolic spikes that indicate some increased pressure in the vessel with heart contraction but without effective flowing of blood through the vessel.

The last signal that is compatible with brain death is a loss of signal entirely indicating no activity in the vessel and no recordable blood flow in the critical vessels of the brain. In conclusion, the concept of brain death has developed with period of the medical field improvements. The absence of a rich uninterrupted supply of oxygen is imperative to supply the brain and maintain unconsciousness and provide for the populations of neurons to continue to function properly.

Trauma, disorders and diseases which impair circulation in the cerebral cortex and brain stem bring about a cascading assortment of symptoms that if not reversed results in death. The protocols and guidelines for brain death determination have been established for the safety of the patient to distinguish between patients who have suffered a life-threatening insult, but who may recover and those unfortunate individuals in whom there is no hope for recovery.

Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system Nervous system From Wikipedia, the free encyclopedia The nervous system is an organ system containing a network of specialized cells called neurons that coordinate the actions of an animal and transmit signals between different parts of its body. In most animals the nervous system consists of two parts, central and peripheral. The central nervous system of vertebrates (such as humans) contains the brain, spinal cord, and retina.

The peripheral nervous system consists of sensory neurons, clusters of neurons called ganglia, and nerves connecting them to each other and to the central nervous system. These regions are all interconnected by means of complex neural pathways. The enteric nervous system, a subsystem of the peripheral nervous system, has the capacity, even when severed from the rest of the nervous system through its primary connection by the vagus nerve, to function independently in controlling the gastrointestinal system. Nervous system

The Human Nervous System. Neurons send signals to other cells as electrochemical waves travelling along thin fibers called axons, which cause systema nervosum Latin chemicals called neurotransmitters to be released at junctions called synapses. A cell that receives a synaptic signal may be excited, inhibited, or otherwise modulated. Sensory neurons are activated by physical stimuli impinging on them, and send signals that inform the central nervous system of the state of the body and the external environment.

Motor neurons, situated either in the central nervous system or in peripheral ganglia, connect the nervous system to muscles or other effector organs. Central neurons, which in vertebrates greatly outnumber the other types, make all of their input and output connections with other neurons. The interactions of all these types of neurons form neural circuits that generate an organism’s perception of the world and determine its behavior. Along with neurons, the nervous system contains other specialized cells called glial cells (or simply glia), which provide structural and metabolic support.

Nervous systems are found in most multicellular animals, but vary greatly in complexity. [1] Sponges have no nervous system, although they have homologs of many genes that play crucial roles in nervous system function, and are capable of several whole-body responses, including a primitive form of locomotion. Placozoans and mesozoans—other simple animals that are not classified as part of the subkingdom Eumetazoa—also have no nervous system. In Radiata (radially symmetric animals such as jellyfish) the nervous system consists of a simple nerve net.

Bilateria, which include the great majority of vertebrates and invertebrates, all have a nervous system containing a brain, one central cord (or two running in parallel), and peripheral nerves. The size of the bilaterian nervous system ranges from a few hundred cells in the simplest worms, to on the order of 100 billion cells in humans. Neuroscience is the study of the nervous system. Contents 1 Structure 1. 1 Cells 1. 1. 1 Neurons 1. 1. 2 Glial cells 1. 2 Anatomy in vertebrates 1. 3 Comparative anatomy and evolution 1. 3. 1 Neural precursors in sponges 1. 3. 2 Radiata 1. 3. 3 Bilateria 1. 3. Worms 1. 3. 5 Arthropods 1. 3. 6 “Identified” neurons 2 Function 2. 1 Neurons and synapses 2. 2 Neural circuits and systems 1 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system 2. 2. 1 Reflexes and other stimulus-response circuits 2. 2. 2 Intrinsic pattern generation 3 Development 4 Pathology 5 References 6 External links Structure The nervous system derives its name from nerves, which are cylindrical bundles of tissue that emanate from the brain and central cord, and branch repeatedly to innervate every part of the body. 2] Nerves are large enough to have been recognized by the ancient Egyptians, Greeks, and Romans,[3] but their internal structure was not understood until it became possible to examine them using a microscope. [4] A microscopic examination shows that nerves consist primarily of the axons of neurons, along with a variety of membranes that wrap around them and segregate them into fascicles. The neurons that give rise to nerves do not lie within them—their cell bodies reside within the brain, central cord, or peripheral ganglia. [2] All animals more advanced than sponges have nervous systems.

However, even sponges, unicellular animals, and non-animals such as slime molds have cell-to-cell signalling mechanisms that are precursors to those of neurons. [5] In radially symmetric animals such as the jellyfish and hydra, the nervous system consists of a diffuse network of isolated cells. [6] In bilaterian animals, which make up the great majority of existing species, the nervous system has a common structure that originated early in the Cambrian period, over 500 million years ago. [7] Cells The nervous system is primarily made up of two categories of cells: neurons and glial cells.

Neurons The nervous system is defined by the presence of a special type of cell—the neuron (sometimes called “neurone” or “nerve cell”). [2] Neurons can be distinguished from other cells in a number of ways, but their most fundamental property is that they communicate with other cells via synapses, which are membrane-to-membrane junctions containing molecular machinery that allows rapid transmission of signals, either electrical or chemical. [2] Many types of neuron possess an axon, a protoplasmic protrusion that can extend to distant parts of the body and make thousands of synaptic contacts. 8] Axons frequently travel through the body in bundles called nerves. Structure of a typical neuron Neuron Even in the nervous system of a single species such as humans, hundreds of different types of neurons exist, with a wide variety of morphologies and functions. [8] These include sensory neurons that transmute physical stimuli such as light and sound into neural signals, and motor neurons that transmute neural signals into activation of muscles or glands; however in many species the great majority of neurons receive all of their input from other neurons and send their output to other neurons. 2] Glial cells Glial cells are non-neuronal cells that provide support and nutrition, maintain homeostasis, form myelin, and participate in signal transmission in the nervous system. [9] In the human brain, it is estimated that the total number of glia roughly equals the number of neurons, although the proportions vary in different brain areas. [10] Among the most important functions of glial cells are to support neurons and hold them in place; to supply nutrients to neurons; to insulate neurons electrically; to destroy pathogens and remove dead neurons; and to 2 of 13 11/5/2010 5:53 PM

Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system provide guidance cues directing the axons of neurons to their targets. [9] A very important type of glial cell (oligodendrocytes in the central nervous system, and Schwann cells in the peripheral nervous system) generates layers of a fatty substance called myelin that wraps around axons and provides electrical insulation which allows them to transmit action potentials much more rapidly and efficiently. Anatomy in vertebrates The nervous system of vertebrate animals (including humans) is divided into he central nervous system (CNS) and peripheral nervous system (PNS). [11] The central nervous system (CNS) is the largest part, and includes the brain and spinal cord. [11] The spinal cavity contains the spinal cord, while the head contains the brain. The CNS is enclosed and protected by meninges, a three-layered system of membranes, including a tough, leathery outer layer called the dura mater. The brain is also protected by the skull, and the spinal cord by the vertebrae. The peripheral nervous system (PNS) is a collective term for the Diagram showing the major divisions of the vertebrate nervous system. ervous system structures that do not lie within the CNS. [12] The large majority of the axon bundles called nerves are considered to belong to the PNS, even when the cell bodies of the neurons to which they belong reside within the brain or spinal cord. The PNS is divided into somatic and visceral parts. The somatic part consists of the nerves that innervate the skin, joints, and muscles. The cell bodies of somatic sensory neurons lie in dorsal root ganglia of the spinal cord. The visceral part, also known as the autonomic nervous system, contains neurons that innervate the internal organs, blood vessels, and glands.

The autonomic nervous system itself consists of two parts: the sympathetic nervous system and the parasympathetic nervous system. Some authors also include sensory neurons whose cell bodies lie in the periphery (for senses such as hearing) as part of the PNS; others, however, omit them. [13] The vertebrate nervous system can also be divided into areas called grey matter (“gray matter” in American spelling) and white matter. [14] Grey matter (which is only grey in preserved tissue, and is better described as pink or light brown in living tissue) contains a high proportion of cell bodies of neurons.

White matter is composed mainly of myelinated axons, and takes its color from the myelin. White matter includes all of the peripheral nerves, and much of the interior of the brain and spinal cord. Grey matter is found in clusters of neurons in the brain and spinal cord, and in cortical layers that line their surfaces. There is an anatomical convention that a cluster of neurons in the brain or spinal cord is called a nucleus, whereas a cluster of neurons in the periphery is called a ganglion. 15] There are, however, a few exceptions to this rule, notably including the part of the forebrain called the basal ganglia. [16] Horizontal bisection of the head of an adult man, showing skin, skull, and brain with grey matter (brown in this image) and underlying white matter Comparative anatomy and evolution Neural precursors in sponges 3 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system Sponges have no cells connected to each other by synaptic junctions, that is, no neurons, and therefore no nervous system.

They do, however, have homologs of many genes that play key roles in synaptic function. Recent studies have shown that sponge cells express a group of proteins that cluster together to form a structure resembling a postsynaptic density (the signal-receiving part of a synapse). [5] However, the function of this structure is currently unclear. Although sponge cells do not show synaptic transmission, they do communicate with each other via calcium waves and other impulses, which mediate some simple actions such as whole-body contraction. 17] Radiata Jellyfish, comb jellies, and related animals have diffuse nerve nets rather than a central nervous system. In most jellyfish the nerve net is spread more or less evenly across the body; in comb jellies it is concentrated near the mouth. The nerve nets consist of sensory neurons that pick up chemical, tactile, and visual signals, motor neurons that can activate contractions of the body wall, and intermediate neurons that detect patterns of activity in the sensory neurons and send signals to groups of motor neurons as a result.

In some cases groups of intermediate neurons are clustered into discrete ganglia. [6] The development of the nervous system in radiata is relatively unstructured. Unlike bilaterians, radiata only have two primordial cell layers, endoderm and ectoderm. Neurons are generated from a special set of ectodermal precursor cells, which also serve as precursors for every other ectodermal cell type. [18] Bilateria The vast majority of existing animals are bilaterians, meaning animals with left and right sides that are approximate mirror images of each other.

All bilateria are thought to have descended from a common wormlike ancestor that appeared in the Cambrian period, 550–600 million years ago. [7] The fundamental bilaterian body form is a tube with a hollow gut cavity running from mouth to anus, and a nerve cord with an enlargement (a “ganglion”) for each body segment, with an especially large ganglion at the front, called the “brain”. Nervous system of a bilaterian animal, in the form of a nerve cord with segmental enlargements, and a “brain” at the front Even mammals, including humans, show the segmented bilaterian body plan at the level of the nervous system.

The spinal cord contains a series of segmental ganglia, each giving rise to motor and sensory nerves that innervate a portion of the body surface and underlying musculature. On the limbs, the layout of the innervation pattern is complex, but on the trunk it gives rise to a series of narrow bands. The top three segments belong to the brain, giving rise to the forebrain, midbrain, and hindbrain. [19] Bilaterians can be divided, based on events that occur very early in embryonic development, into two groups (superphyla) called protostomes and deuterostomes. 20] Deuterostomes include vertebrates as well as echinoderms, hemichordates (mainly acorn worms), and Xenoturbellidans. [21] Protostomes, the more diverse group, include arthropods, molluscs, and numerous types of worms. There is a basic difference between the two groups in the placement of the nervous system within the body: protostomes possess a nerve cord on the ventral (usually bottom) side of the body, Area of the human whereas in deuterostomes the nerve cord is on the dorsal (usually top) side.

In fact, body surface numerous aspects of the body are inverted between the two groups, including the innervated by each expression patterns of several genes that show dorsal-to-ventral gradients. Most spinal nerve anatomists now consider that the bodies of protostomes and deuterostomes are “flipped over” with respect to each other, a hypothesis that was first proposed by Geoffroy Saint-Hilaire for insects in comparison to vertebrates. Thus insects, for example, have nerve cords that run along the ventral midline of the body, while all vertebrates have spinal cords that un along the dorsal midline. [22] Worms 4 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system Worms are the simplest bilaterian animals, and reveal the basic structure of the bilaterian nervous system in the most straightforward way. As an example, earthworms have dual nerve cords running along the length of the body and merging at the tail and the mouth. These nerve cords are connected by transverse nerves like the rungs of a ladder. These transverse nerves help coordinate the two sides of the animal.

Two ganglia at the head end function similar to a simple brain. Photoreceptors on the animal’s eyespots provide sensory information on light and dark. [23] Earthworm nervous system. Top: side The nervous system of one very small worm, the roundworm view of the front of the worm. Bottom: Caenorhabditis elegans, has been mapped out down to the synaptic nervous system in isolation, viewed level. Every neuron and its cellular lineage has been recorded and from above most, if not all, of the neural connections are known.

In this species, the nervous system is sexually dimorphic; the nervous systems of the two sexes, males and hermaphrodites, have different numbers of neurons and groups of neurons that perform sex-specific functions. In C. elegans, males have exactly 383 neurons, while hermaphrodites have exactly 302 neurons. [24] Arthropods Arthropods, such as insects and crustaceans, have a nervous system made up of a series of ganglia, connected by a ventral nerve cord made up of two parallel connectives running along the length of the belly. 25] Typically, each body segment has one ganglion on each side, though some ganglia are fused to form the brain and other large ganglia. The head segment contains the brain, also known as the supraesophageal ganglion. In the insect nervous system, the Internal anatomy of a spider, showing brain is anatomically divided into the protocerebrum, the nervous system in blue deutocerebrum, and tritocerebrum. Immediately behind the brain is the subesophageal ganglion, which is composed of three pairs of fused ganglia. It controls the mouthparts, the salivary glands and certain muscles.

Many arthropods have well-developed sensory organs, including compound eyes for vision and antennae for olfaction and pheromone sensation. The sensory information from these organs is processed by the brain. In insects, many neurons have cell bodies that are positioned at the edge of the brain and are electrically passive—the cell bodies serve only to provide metabolic support and do not participate in signalling. A protoplasmic fiber runs from the cell body and branches profusely, with some parts transmitting signals and other parts receiving signals.

Thus, most parts of the insect brain have passive cell bodies arranged around the periphery, while the neural signal processing takes place in a tangle of protoplasmic fibers called neuropil, in the interior. [26] “Identified” neurons A neuron is called identified if it has properties that distinguish it from every other neuron in the same animal —properties such as location, neurotransmitter, gene expression pattern, and connectivity—and if every individual organism belonging to the same species has one and only one neuron with the same set of properties. 27] In vertebrate nervous systems very few neurons are “identified” in this sense—in humans, there are believed to be none—but in simpler nervous systems, some or all neurons may be thus unique. In the roundworm C. elegans, whose nervous system is the most thoroughly described of any animal’s, every neuron in the body is uniquely identifiable, with the same location and the same connections in every individual worm. One notable consequence of this fact is that the form of the C. elegans nervous system is completely specified by the genome, with no experience-dependent plasticity. 24] The brains of many molluscs and insects also contain substantial numbers of identified neurons. [27] In vertebrates, the best known identified neurons are the gigantic Mauthner cells of fish. [28] Every fish has two Mauthner cells, located in the bottom part of the brainstem, one on the left side and one on the right. Each Mauthner cell has an axon that crosses over, innervating neurons at the same brain level and then travelling down through the spinal cord, making numerous connections as it goes. The synapses generated by a Mauthner cell are so owerful that a single action potential gives rise to a major behavioral response: within milliseconds the fish curves its body into a C-shape, then straightens, thereby propelling itself rapidly forward. Functionally this is a fast escape response, triggered most easily by a strong sound wave or pressure wave impinging on the lateral line organ of the fish. Mauther cells are not the only identified neurons in fish—there are about 20 more 5 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. ikipedia. org/wiki/Nervous_system types, including pairs of “Mauthner cell analogs” in each spinal segmental nucleus. Although a Mauthner cell is capable of bringing about an escape response all by itself, in the context of ordinary behavior other types of cells usually contribute to shaping the amplitude and direction of the response. Mauthner cells have been described as command neurons. A command neuron is a special type of identified neuron, defined as a neuron that is capable of driving a specific behavior all by itself. 29] Such neurons appear most commonly in the fast escape systems of various species—the squid giant axon and squid giant synapse, used for pioneering experiments in neurophysiology because of their enormous size, both participate in the fast escape circuit of the squid. The concept of a command neuron has, however, become controversial, because of studies showing that some neurons that initially appeared to fit the description were really only capable of evoking a response in a limited set of circumstances. [30] Function

At the most basic level, the function of the nervous system is to send signals from one cell to others, or from one part of the body to others. There are multiple ways that a cell can send signals to other cells. One is by releasing chemicals called hormones into the internal circulation, so that they can diffuse to distant sites. In contrast to this “broadcast” mode of signaling, the nervous system provides “point-to-point” signals—neurons project their axons to specific target areas and make synaptic connections with specific target cells. 31] Thus, neural signaling is capable of a much higher level of specificity than hormonal signaling. It is also much faster: the fastest nerve signals travel at speeds that exceed 100 meters per second. At a more integrative level, the primary function of the nervous system is to control the body. [2] It does this by extracting information from the environment using sensory receptors, sending signals that encode this information into the central nervous system, processing the information to determine an appropriate response, and sending output signals to muscles or glands to activate the response.

The evolution of a complex nervous system has made it possible for various animal species to have advanced perception abilities such as vision, complex social interactions, rapid coordination of organ systems, and integrated processing of concurrent signals. In humans, the sophistication of the nervous system makes it possible to have language, abstract representation of concepts, transmission of culture, and many other features of human society that would not exist without the human brain. Neurons and synapses 6 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system

Most neurons send signals via their axons, although some types are capable of dendrite-to-dendrite communication. (In fact, the types of neurons called amacrine cells have no axons, and communicate only via their dendrites. ) Neural signals propagate along an axon in the form of electrochemical waves called action potentials, which produce cell-to-cell signals at points where axon terminals make synaptic contact with other cells. [32] Synapses may be electrical or chemical. Electrical synapses make direct electrical connections between neurons,[33] but chemical synapses are much more common, and much more diverse in function. 34] At a chemical synapse, the cell that sends signals is called presynaptic, and the cell that receives signals is called postsynaptic. Both the presynaptic and postsynaptic areas are full of molecular machinery that carries out the signalling process. The presynaptic area contains large numbers of tiny spherical vessels called synaptic vesicles, packed with neurotransmitter chemicals. [32] When the presynaptic terminal is electrically stimulated, an array of molecules embedded in the membrane are Major elements in synaptic transmission.

An activated, and cause the contents of the vesicles to electrochemical wave called an action potential travels along the axon of a neuron. When the wave reaches a be released into the narrow space between the synapse, it provokes release of a puff of presynaptic and postsynaptic membranes, called the neurotransmitter molecules, which bind to chemical synaptic cleft. The neurotransmitter then binds to receptor molecules located in the membrane of the target receptors embedded in the postsynaptic membrane, cell. causing them to enter an activated state. 34] Depending on the type of receptor, the resulting effect on the postsynaptic cell may be excitatory, inhibitory, or modulatory in more complex ways. For example, release of the neurotransmitter acetylcholine at a synaptic contact between a motor neuron and a muscle cell induces rapid contraction of the muscle cell. [35] The entire synaptic transmission process takes only a fraction of a millisecond, although the effects on the postsynaptic cell may last much longer (even indefinitely, in cases where the synaptic signal leads to the formation of a memory trace). 8] There are literally hundreds of different Structure of a typical chemical synapse types of synapses. In fact, there are over a hundred known neurotransmitters, and many of them have multiple types of receptor. [36] Many synapses use more than one neurotransmitter—a common arrangement is for a synapse to use one fast-acting smallmolecule neurotransmitter such as glutamate gated Ca or GABA, along with one or more peptide neurotransmitters that play slower-acting modulatory roles. Molecular neuroscientists generally divide receptors into two broad Postsynaptic groups: chemically ated ion channels and second messenger systems. When a chemically gated ion channel is activated, it forms a passage that allow specific types of ion to flow across the membrane. Depending on the type of ion, the effect on the target cell may be excitatory or inhibitory. When a second messenger system is activated, it starts a cascade of molecular interactions inside the target cell, which may ultimately produce a wide variety of complex effects, such as increasing or decreasing the sensitivity of the cell to stimuli, or even altering gene transcription.

According to a rule called Dale’s principle, which has only a few known exceptions, a neuron releases the same neurotransmitters at all of its synapses. [37] This does not mean, though, that a neuron exerts the same effect on all of its targets, because the effect of a synapse depends not on the neurotransmitter, but on the receptors that it activates. [34] Because different targets can (and frequently do) use different types of receptors, it is possible for a neuron to have excitatory effects on one set of target cells, inhibitory effects on others, and complex 7 of 13 11/5/2010 5:53 PM

Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system modulatory effects on others still. Nevertheless, it happens that the two most widely used neurotransmitters, glutamate and GABA, each have largely consistent effects. Glutamate has several widely occurring types of receptors, but all of them are excitatory or modulatory. Similarly, GABA has several widely occurring receptor types, but all of them are inhibitory. [38] Because of this consistency, glutamatergic cells are frequently referred to as “excitatory neurons”, and GABAergic cells as “inhibitory neurons”.

Strictly speaking this is an abuse of terminology—it is the receptors that are excitatory and inhibitory, not the neurons—but it is commonly seen even in scholarly publications. One very important subset of synapses are capable of forming memory traces by means of long-lasting activitydependent changes in synaptic strength. [39] The best-known form of neural memory is a process called long-term potentiation (abbreviated LTP), which operates at synapses that use the neurotransmitter glutamate acting on a special type of receptor known as the NMDA receptor. 40] The NMDA receptor has an “associative” property: if the two cells involved in the synapse are both activated at approximately the same time, a channel opens that permits calcium to flow into the target cell. [41] The calcium entry initiates a second messenger cascade that ultimately leads to an increase in the number of glutamate receptors in the target cell, thereby increasing the effective strength of the synapse.

This change in strength can last for weeks or longer. Since the discovery of LTP in 1973, many other types of synaptic memory traces have been found, involving increases or decreases in synaptic strength that are induced by varying conditions, and last for variable periods of time. [40] Reward learning, for example, depends on a variant form of LTP that is conditioned on an extra input coming from a reward-signalling pathway that uses dopamine as neurotransmitter. 42] All these forms of synaptic modifiability, taken collectively, give rise to neural plasticity, that is, to a capability for the nervous system to adapt itself to variations in the environment. Neural circuits and systems The basic neuronal function of sending signals to other cells includes a capability for neurons to exchange signals with each other. Networks formed by interconnected groups of neurons are capable of a wide variety of functions, including feature detection, pattern generation, and timing. 43] In fact, it is difficult to assign limits to the types of information processing that can be carried out by neural networks: Warren McCulloch and Walter Pitts showed in 1943 that even networks formed from a greatly simplified mathematical abstraction of a neuron are capable of universal computation. [44] Given that individual neurons can generate complex temporal patterns of activity all by themselves, the range of capabilities possible for even small groups of interconnected neurons are beyond current understanding. 43] Historically, for many years the predominant view of the function of the nervous system was as a stimulus-response associator. [45] In this conception, neural processing begins with stimuli that activate sensory neurons, producing signals that propagate through chains of connections in the spinal cord and brain, giving rise eventually to activation of motor neurons and thereby to muscle contraction, i. e. , to overt responses.

Descartes believed that all of the behaviors of animals, and most of the behaviors of humans, could be explained in terms of stimulus-response circuits, although he also believed that higher cognitive functions such as language were not capable of being explained mechanistically. [46] Charles Sherrington, in his influential 1906 book The Integrative Action of the Nervous System,[45] developed the concept of stimulus-response mechanisms in much more detail, and Behaviorism, the school of thought that dominated Psychology through the middle of the 20th century, attempted to explain every aspect of human behavior in stimulus-response terms. 47] Illustration of pain pathway, from Rene Descartes’s Treatise of Man However, experimental studies of electrophysiology, beginning in the early 20th century and reaching high productivity by the 1940s, showed that the nervous system contains many mechanisms for generating patterns of activity intrinsically, without requiring an external stimulus. [48] Neurons were found to be capable of producing regular sequences of action potentials, or sequences of bursts, even in complete isolation. 49] When intrinsically active neurons are connected to each other in complex circuits, the possibilities for generating intricate temporal patterns become far more extensive. [43] A modern conception views the function of the nervous system partly in terms of stimulus-response chains, and partly in terms of intrinsically generated activity patterns—both types of activity interact with each other to generate the full repertoire of behavior. [50] Reflexes and other stimulus-response circuits 8 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia ttp://en. wikipedia. org/wiki/Nervous_system The simplest type of neural circuit is a reflex arc, which begins with a sensory input and ends with a motor output, passing through a sequence of neurons in between. [51] For example, consider the “withdrawal reflex” causing the hand to jerk back after a hot stove is touched. The circuit begins with sensory receptors in the skin that are activated by harmful levels of heat: a special type of molecular structure embedded in the membrane causes heat to generate an electrical field across the membrane.

If the electrical potential change is large enough, it evokes an action potential, which is transmitted along the axon of the receptor cell, into the spinal cord. There the axon makes excitatory synaptic contacts with other cells, some of which project to the Simplified schema of basic nervous system function: signals are same region of the spinal cord, others picked up by sensory receptors and sent to the spinal cord and projecting into the brain.

One target is a set brain, where processing occurs that results in signals sent back of spinal interneurons that project to motor to the spinal cord and then out to motor neurons neurons controlling the arm muscles. The interneurons excite the motor neurons, and if the excitation is strong enough, some of the motor neurons generate action potentials, which travel down their axons to the point where they make excitatory synaptic contacts with muscle cells. The excitatory signals induce contraction of the muscle cells, which causes the joint angles in the arm to change, pulling the arm away.

In reality, this straightfoward schema is subject to numerous complications. [51] Although for the simplest reflexes there are short neural paths from sensory neuron to motor neuron, there are also other nearby neurons that participate in the circuit and modulate the response. Furthermore, there are projections from the brain to the spinal cord that are capable of enhancing or inhibiting the reflex. Although the simplest reflexes may be mediated by circuits lying entirely within the spinal cord, more complex responses rely on signal processing in the brain. 52] Consider, for example, what happens when an object in the periphery of the visual field moves, and a person looks toward it. The initial sensory response, in the retina of the eye, and the final motor response, in the oculomotor nuclei of the brain stem, are not all that different from those in a simple reflex, but the intermediate stages are completely different. Instead of a one or two step chain of processing, the visual signals pass through perhaps a dozen stages of integration, involving the thalamus, cerebral cortex, basal ganglia, superior colliculus, cerebellum, and several brainstem nuclei.

These areas perform signal-processing functions that include feature detection, perceptual analysis, memory recall, decision-making, and motor planning. [53] Feature detection is the ability to extract biologically relevant information from combinations of sensory signals. [54] In the visual system, for example, sensory receptors in the retina of the eye are only individually capable of detecting “points of light” in the outside world. [55] Second-level visual neurons receive input from groups of primary receptors, higher-level neurons receive input from groups of second-level neurons, and so on, forming a hierarchy of processing stages.

At each stage, important information is extracted from the signal ensemble and unimportant information is discarded. By the end of the process, input signals representing “points of light” have been transformed into a neural representation of objects in the surrounding world and their properties. The most sophisticated sensory processing occurs inside the brain, but complex feature extraction also takes place in the spinal cord and in peripheral sensory organs such as the retina.

Intrinsic pattern generation Although stimulus-response mechanisms are the easiest to understand, the nervous system is also capable of controlling the body in ways that do not require an external stimulus, by means of internally generated rhythms of activity. Because of the variety of voltage-sensitive ion channels that can be embedded in the membrane of a neuron, many types of neurons are capable, even in isolation, of generating rhythmic sequences of action potentials, or rhymthic alternations between high-rate bursting and quiessence.

When neurons that are intrinsically rhythmic are connected to each other by excitatory or inhibitory synapses, the resulting networks are capable of a wide variety of dynamical behaviors, including attractor dynamics, periodicity, and even chaos. A network of neurons that uses its internal structure to generate temporally structured output, without requiring a corresponding temporally structured stimulus, is called a central pattern generator. 9 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system

Internal pattern generation operates on a wide range of time scales, from milliseconds to hours or longer. One of the most important types of temporal pattern is circadian rhythmicity—that is, rhythmicity with a period of approximately 24 hours. All animals that have been studied show circadian fluctuations in neural activity, which control circadian alternations in behavior such as the sleep-wake cycle. Experimental studies dating from the 1990s have shown that circadian rhythms are generated by a “genetic clock” consisting of a special set of genes whose expression level rises and falls over the course of the day.

Animals as diverse as insects and vertebrates share a similar genetic clock system. The circadian clock is influenced by light but continues to operate even when light levels are held constant and no other external time-of-day cues are available. The clock genes are expressed in many parts of the nervous system as well as many peripheral organs, but in mammals all of these “tissue clocks” are kept in synchrony by signals that emanate from a master timekeeper in a tiny part of the brain called the suprachiasmatic nucleus. Development

In vertebrates, landmarks of embryonic neural development include the birth and differentiation of neurons from stem cell precursors, the migration of immature neurons from their birthplaces in the embryo to their final positions, outgrowth of axons from neurons and guidance of the motile growth cone through the embryo towards postsynaptic partners, the generation of synapses between these axons and their postsynaptic partners, and finally the lifelong changes in synapses which are thought to underlie learning and memory. 56] All bilaterian animals at an early stage of development form a gastrula, which is polarized, with one end called the animal pole and the other the vegetal pole. The gastrula has the shape of a disk with three layers of cells, an inner layer called the endoderm, which gives rise to the lining of most internal organs, a middle layer called the mesoderm, which gives rise to the bones and muscles, and an outer layer called the ectoderm, which gives rise to the skin and nervous system. [57] Human embryo, showing neural groove

Four stages in the development of the neural tube in the human embryo In vertebrates, the first sign of the nervous system is the appearance of a thin strip of cells along the center of the back, called the neural plate. The inner portion of the neural plate (along the midline) is destined to become the central nervous system (CNS), the outer portion the peripheral nervous system (PNS). As development proceeds, a fold called the neural groove appears along the midline. This fold deepens, and then closes up at the top.

At this point the future CNS appears as a cylindrical structure called the neural tube, whereas the future PNS appears as two strips of tissue called the neural crest, running lengthwise above the neural tube. The sequence of stages from neural plate to neural tube and neural crest is known as neurulation. In the early 20th century, a set of famous experiments by Hans Spemann and Hilde Mangold showed that the formation of nervous tissue is “induced” by the underlying mesoderm. For decades, though, the nature of the induction process defeated every attempt to figure it out, until finally it was resolved by genetic approaches in the 1990s.

Induction of neural tissue requires inhibition of the gene for a so-called bone morphogenetic protein, or BMP. Specifically the protein BMP4 appears to be involved. Two proteins called Noggin and Chordin, both secreted by the mesoderm, are capable of inhibiting BMP4 and thereby inducing ectoderm to turn into neural tissue. It appears that a similar molecular mechanism is involved for widely disparate types of animals, including arthropods as well as vertebrates. In some animals, however, another type of molecule called Fibroblast Growth Factor or FGF may also play an important role in induction.

Induction of neural tissues causes formation of neural precursor cells, called neuroblasts. [58] In drosophila, neuroblasts divide asymmetically, so that one product is a “ganglion mother cell” (GMC), and the other is a 10 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system neuroblast. A GMC divides once, to give rise to either a pair of neurons or a pair of glial cells. In all, a neuroblast is capable of generating an indefinite number of neurons or glia.

As shown in a 2008 study, one factor common to all bilateral organisms (including humans) is a family of secreted signaling molecules called neurotrophins which regulate the growth and survival of neurons. [59] Zhu et al. identified DNT1, the first neurotrophin found in flies. DNT1 shares structural similarity with all known neurotrophins and is a key factor in the fate of neurons in Drosophila. Because neurotrophins have now been identified in both vertebrate and invertebrates, this evidence suggests that neurotrophins were present in an ancestor common to bilateral organisms and may represent a common mechanism for nervous system formation.

Pathology Main article: Neurology See also: Psychiatry The nervous system is susceptible to malfunction in a wide variety of ways, as a result of genetic defects, physical damage due to trauma or poison, infection, or simply aging. The medical specialty of neurology studies the causes of nervous system malfunction, and looks for interventions that can alleviate it. The central nervous system is protected by major physical and chemical barriers. Physically, the brain and spinal cord are surrounded by tough meningeal membranes, and enclosed in the bones of the skull and spinal vertebrae, which combine to form a strong physical shield.

Chemically, the brain and spinal cord are isolated by the so-called blood-brain barrier, which prevents most types of chemicals from moving from the bloodstream into the interior of the CNS. These protections make the CNS less susceptible in many ways than the PNS; the flip side, however, is that damage to the CNS tends to have more serious consequences. Although peripheral nerves tend to lie deep under the skin except in a few places such as the elbow joint, they are still relatively exposed to physical damage, which can cause pain, loss of sensation, or loss of muscle control.

Damage to nerves can also be caused by swelling or bruises at places where a nerve passes through a tight bony channel, as happens in carpal tunnel syndrome. If a peripheral nerve is completely transected, it will often regenerate, but for long nerves this process may take months to complete. In addition to physical damage, peripheral neuropathy may be caused by many other medical problems, including genetic conditions, metabolic conditions such as diabetes, inflammatory conditions such as Guillain-Barre syndrome, vitamin deficiency, infectious diseases such as leprosy or shingles, or poisoning by toxins such as heavy metals.

Many cases have no cause that can be identified, and are referred to as idiopathic. It is also possible for peripheral nerves to lose function temporarily, resulting in numbness as stiffness—common causes include mechanical pressure, a drop in temperature, or chemical interactions with local anesthetic drugs such as lidocaine. Physical damage to the spinal cord may result in loss of sensation or movement. If an injury to the spine produces nothing worse than swelling, the symptoms may be transient, but if nerve fibers in the spine are actually destroyed, the loss of function is usually permanent.

Experimental studies have shown that spinal nerve fibers attempt to regrow in the same way as peripheral nerve fibers, but in the spinal cord, tissue destruction usually produces scar tissue that cannot be penetrated by the regrowing nerves. References 1. ^ “Nervous System”. Columbia Encyclopedia. Columbia University Press. 2. ^ a b c d e f Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 2: Nerve cells and behavior”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. 3. ^ Finger S (2001). “Ch. 1: The brain in antiquity”. Origins of neuroscience: a history of explorations into brain function.

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Development 129 (13): 3021–32. PMID 12070079 (http://www. ncbi. nlm. nih. gov/pubmed/12070079) . ^ Bourlat SJ, Juliusdottir T, Lowe CJ, et al. (November 2006). “Deuterostome phylogeny reveals monophyletic chordates and the new phylum Xenoturbellida”. Nature 444 (7115): 85–8. doi:10. 1038/nature05241 (http://dx. doi. org /10. 1038%2Fnature05241) . PMID 17051155 (http://www. ncbi. nlm. nih. gov/pubmed/17051155) . ^ Lichtneckert R, Reichert H (May 2005). “Insights into the urbilaterian brain: conserved genetic patterning mechanisms in insect and vertebrate brain development”. Heredity 94 (5): 465–77. doi:10. 038/sj. hdy. 6800664 (http://dx. doi. org /10. 1038%2Fsj. hdy. 6800664) . PMID 15770230 (http://www. ncbi. nlm. nih. gov/pubmed/15770230) . ^ ADEY WR (February 1951). “The nervous system of the earthworm Megascolex”. J. Comp. Neurol. 94 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 36. 37. 38. 39. 40. (1): 57–103. doi:10. 1002/cne. 900940104 (http://dx. doi. org/10. 1002%2Fcne. 900940104) . PMID 14814220 (http://www. ncbi. nlm. nih. gov /pubmed/14814220) . ^ a b “Wormbook: Specification of the nervous system” (http://www. wormbook. org/chapters /www_specnervsys/specnervsys. html) . http://www. wormbook. rg/chapters /www_specnervsys/specnervsys. html. ^ Chapman RF (1998). “Ch. 20: Nervous system”. The insects: structure and function. Cambridge University Press. pp. 533–568. ISBN 9780521578905. ^ Chapman, p. 546 ^ a b Hoyle G, Wiersma CAG (1977). Identified neurons and behavior of arthropods. Plenum Press. ISBN 9780306310010. ^ Stein PSG (1999). Neurons, Networks, and Motor Behavior. MIT Press. pp. 38–44. ISBN 9780262692274. ^ Stein, p. 112 ^ Simmons PJ, Young D (1999). Nerve cells and animal behaviour. Cambridge University Press. p. 43. ISBN 9780521627269. ^ Gray PO (2006). Psychology (5 ed. ). Macmillan. p. 170.

ISBN 9780716776901. ^ a b Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 9: Propagated signaling: the action potential”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Hormuzdi SG, Filippov MA, Mitropoulou G, et al. (2004). “Electrical synapses: a dynamic signaling system that shapes the activity of neuronal networks”. Biochim. Biophys. Acta 1662 (1-2): 113–37. doi:10. 1016/j. bbamem. 2003. 10. 023 (http://dx. doi. org /10. 1016%2Fj. bbamem. 2003. 10. 023) . PMID 15033583 (http://www. ncbi. nlm. nih. gov /pubmed/15033583) . ^ a b c Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 0: Overview of synaptic transmission”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 11: Signaling at the nerve-muscle synapse”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 15: Neurotransmitters”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Strata P, Harvey R (1999). “Dale’s principle”. Brain Res. Bull. 50 (5-6): 349–50. doi:10. 1016/S0361-9230(99)00100-8 (http://dx. doi. org /10. 1016%2FS0361-9230%2899%2900100-8) .

PMID 10643431 (http://www. ncbi. nlm. nih. gov /pubmed/10643431) . ^ There are a number of exceptional situations in which GABA has been found to have excitatory effects, mainly during early development. For a review see Marty A, Llano I (June 2005). “Excitatory effects of GABA in established brain networks”. Trends Neurosci. 28 (6): 284–9. doi:10. 1016/j. tins. 2005. 04. 003 (http://dx. doi. org /10. 1016%2Fj. tins. 2005. 04. 003) . PMID 15927683 (http://www. ncbi. nlm. nih. gov/pubmed/15927683) . ^ Paradiso MA; Bear MF; Connors BW (2007). Neuroscience: Exploring the Brain. Lippincott Williams & Wilkins. p. 18. ISBN 0-7817-6003-8. ^ a b Cooke SF, Bliss TV (2006). “Plasticity in the 12 of 13 11/5/2010 5:53 PM Nervous system – Wikipedia, the free encyclopedia http://en. wikipedia. org/wiki/Nervous_system 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. human central nervous system”. Brain 129 (Pt 7): 1659–73. doi:10. 1093/brain/awl082 (http://dx. doi. org /10. 1093%2Fbrain%2Fawl082) . PMID 16672292 (http://www. ncbi. nlm. nih. gov/pubmed/16672292) . ^ Bliss TV, Collingridge GL (January 1993). “A synaptic model of memory: long-term potentiation in the hippocampus”. Nature 361 (6407): 31–9. doi:10. 1038/361031a0 (http://dx. oi. org /10. 1038%2F361031a0) . PMID 8421494 (http://www. ncbi. nlm. nih. gov/pubmed/8421494) . ^ Kauer JA, Malenka RC (November 2007). “Synaptic plasticity and addiction”. Nat. Rev. Neurosci. 8 (11): 844–58. doi:10. 1038/nrn2234 (http://dx. doi. org/10. 1038%2Fnrn2234) . PMID 17948030 (http://www. ncbi. nlm. nih. gov /pubmed/17948030) . ^ a b c Dayan P, Abbott LF (2005). Theoretical Neuroscience: Computational and Mathematical Modeling of Neural Systems. MIT Press. ISBN 9780262541855. ^ McCulloch WS, Pitts W (1943). “A logical calculus of the ideas immanent in nervous activity”. Bull. Math. Biophys. : 115–133. doi:10. 1007/BF02478259 (http://dx. doi. org /10. 1007%2FBF02478259) . ^ a b Sherrington CS (1906). The Integrative Action of the Nervous System (http://books. google. com /? id=6KwRAAAAYAAJ) . Scribner. http://books. google. com/? id=6KwRAAAAYAAJ. ^ Descartes R (1989). Passions of the Soul. Voss S. Hackett. ISBN 9780872200357. ^ Baum WM (2005). Understanding behaviorism: Behavior, Culture and Evolution. Blackwell. ISBN 9781405112628. ^ Piccolino M (November 2002). “Fifty years of the Hodgkin-Huxley era”. Trends Neurosci. 25 (11): 552–3. doi:10. 1016/S0166-2236(02)02276-2 (http://dx. oi. org /10. 1016%2FS0166-2236%2802%2902276-2) . PMID 12392928 (http://www. ncbi. nlm. nih. gov /pubmed/12392928) . ^ Johnston D, Wu SM (1995). Foundations of cellular neurophysiology. MIT Press. ISBN 9780262100533. ^ Simmons PJ, Young D (1999). “Ch 1. : 51. 52. 53. 54. 55. 56. 57. 58. 59. Introduction”. Nerve cells and animal behaviour. Cambridge Univ. Press. ISBN 9780521627269. ^ a b Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 36: Spinal reflexes”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). Ch. 38: Voluntary movement”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 39: The control of gaze”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 21: Coding of sensory information”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 25: Constructing the visual image”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 52: The induction and patterning of the nervous system”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Sanes DH, Reh TH, Harris WA (2006). “Ch. 1, Neural induction”. Development of the Nervous System. Elsevier Academic Press. ISBN 9780126186215. ^ Kandel ER, Schwartz JH, Jessel TM, ed (2000). “Ch. 53: The formation and survival of nerve cells”. Principles of Neural Science. McGraw-Hill Professional. ISBN 9780838577011. ^ Zhu B, Pennack JA, McQuilton P, Forero MG, Mizuguchi K, Sutcliffe B, Gu CJ, Fenton JC, Hidalgo A (Nov 2008). Drosophila neurotrophins reveal a common mechanism for nervous system formation” (http://scivee. tv/node/8389) . PLoS Biol 6 (11): e284. doi:10. 1371/journal. pbio. 0060284 (http://dx. doi. org /10. 1371%2Fjournal. pbio. 0060284) . PMID 19018662 (http://www. ncbi. nlm. nih. gov /pubmed/19018662) . PMC 2586362 (http://www. pubmedcentral. gov /articlerender. fcgi? tool=pmcentrez&artid=2586362) . http://scivee. tv/node/8389. External links Neuroscience for Kids (http://faculty. washington. edu/chudler/introb. html) The Human Brain Project Homepage (http://www. thehumanbrainproject. org) Kimball’s Biology Pages, CNS (http://users. cn. com/jkimball. ma. ultranet/BiologyPages/C/CNS. html) Kimball’s Biology Pages, PNS (http://users. rcn. com/jkimball. ma. ultranet/BiologyPages/P/PNS. html) Retrieved from “http://en. wikipedia. org/wiki/Nervous_system” Categories: Nervous system | Neurobiology | Neuroscience This page was last modified on 2 November 2010 at 22:23. Text is available under the Creative Commons Attribution-ShareAlike License; additional terms may apply. See Terms of Use for details. Wikipedia® is a registered trademark of the Wikimedia Foundation, Inc. , a non-profit organization. 13 of 13 11/5/2010 5:53 PM

Mars Is a delightful and enlightening book that reveals the unparalleled complexity of the human brain. Sacks, an accomplished neurologist and author, presents seven case studies that highlight different neurological phenomena. In his case studies, Sacks follows a newly colliding painter, a man who can create no new memories, a surgeon with Trustee’s syndrome, a blind man who regains his sight, a painter obsessed with images from his childhood, an autistic boy artist, and a high-functioning autistic roofless.

Sacks does not treat his case studies as dry medical oddities but rather discusses their neurological experiences within their broader human existence. Unlike other authors who know their patients only distantly, Sacks works intimately with his case studies and develops meaningful relationships that translate into a deeper, more Insightful understanding of his patients and their experiences. While Sacks Is clearly a brilliant neurologist, what makes this book so powerful Is his ability to weave In medicine, science, history, and philosophy Into a coherent narrative.

Every case study illuminates a series of important and thought-provoking questions that challenge the everyday assumptions of perception, reality, intelligence, and what it means to be human. In the end, the reader emerges with a better appreciation of the complexity of the human mind. Sacks does not look at simply the pathological and physiological way that the disease affects the individual but how the individual reacts to the disorder and how, in each of these cases, they retain their own sense of self despite what the disease/doodler does to them.

Sacks does not Just throw a barrage of patients with neurological scissors at the reader, but rather goes through the lives of seven patients and observes them In their natural life. He presents not only their disorder, but how It affects their daily life, how their perception of the world is different, and the creative ways that they have come up to deal with their disorder. According to his case studies and brief synopsis there are seven cases he presented in the book.

One is “The Case of the Colliding Painter this case his case talks about the predicament of a painter who after sixty five years had an accident which robbed him entirely of his color vision. A man, who had had a distinguished career as an artist with numerous vividly colored paintings and abstractions In his studio, could no longer even Imagine color. The painter eventually accepted his predicament and started to paint black-and-white representations Instead of dwelling on the loss of his ability to paint In color.

As Sacks explains, “… A revision was occurring, so that as his former color world and even the memory of it became fainter and died inside also involves an artist who loses his color perception ability after an accident. “Would it be “normal” from the moment vision was restored? Was not experience necessary to see? Did one have to learn to see? ” (Sacks 109). The author details the patient cases and uses it as one of the ways in giving an account of how the modern understanding of vision works.

From this, there are lessons learnt from the inability of the artist to also remember the colors. The diseases focused on in the essays affect the ways in which individuals know and understand themselves.. In this case they call this illness is “Cerebral achromatic is a type of color-blindness caused by damage to the cerebral cortex of the brain, rather than abnormalities in the cells of he eye’s retina. It is often confused with congenital achromatic but underlying physiological deficits of the disorders are completely distinct.

It is shows the signs and symptoms of Patients with cerebral achromatic deny having any experience of color when asked and fail standard clinical assessments like the Farnsworth- Mussels 100-hue test (a test of color ordering with no naming requirements). Patients may often not notice their loss of color vision and merely describe the world they see as being “drab”. Most describe seeing the world in “shades of gray”. This observation totes a key difference between cerebral and congenital achromatic, as those born with achromatic have never had an experience of color or gray.

It can diagnosis he most common tests perform to diagnose cerebral achromatic are the Farnsworth-Mussels 100-hue test, the Ashier plate test, and the color-naming test. Testing and diagnosis for cerebral achromatic is often incomplete and misdiagnosed in doctor’s offices. 2 Remarkably, almost 50% of tested patients diagnosed with cerebral achromatic are able to perform normally on the color-naming test. However, these results are Mathew in question because of the sources from which many of these reports come.

Only 29% of cerebral achromatic patients successfully pass the Ashier plate test, which is a more accepted and more standardized test for color blindness. In order for one to be in a position to understand their subjects appropriately, the personality method of investigation is vital. Therefore, spending ample time with your subjects is very crucial in this field. I find “An anthropologist on Mars” fascinating since it gives man opportunity to view peoples’ brains conditions as well as study them to the letter. The fascinating neurological stories explore some of the unique experiences and perceptions of oneself.

The saddest thing about the study on disorders of the nervous system and the brain is that the condition of most of the patients is beyond repair. This is irrespective of the diverse scope of knowledge in the book. The passion in me to know more about science related cases especially on first hand authors method of finding ways to help patients to be fit again is fantastic. I arrive to this conclusion after reading how he has tackled cases in certain disorders facing the neuron system and the brain. These are Kormas syndrome and Trustees syndrome.

Patients in these unusual disorders should be given information on how to cope to the conditions they find themselves in. This should be done without necessarily considering whether the patient’s outcome. All the professionals involved in this field should incorporate this idea into their profession to spur them to enviable success. In addition, utilizing different neurological techniques to learn each of the subjects in a respectful and personal manner is also important. 3 Most of those operating in this field tend to go by the results given by the clinic.

However, this is not always advisable since you maybe condemning someone to a their death whereas a lot can be done to improve his condition. Having the curiosity to discover the beauty in the minds of the affected people will help you achieve this goal far much easier. All this should be done in environments that make the affected feel comfortable rather than undermined. This is through creating time for private outings with every patient you are in contact with as well making arrangements to bond with them through their activities. This enables one to learn more and figure out their problems.

Being a step ahead and having better ideas on how to treat the individual under medical examination is also important. Each of the chapters in “An anthropologist on Mars” has a cast of significant characters, setting, and plot. The elements portrayed in the book weave together creating a fascinating story. The individuals undergoing examination are astonishing and how the author manages to counter the sterile account of the relative neurological functioning found in psychiatric Journals is brilliant. I am amazed by how the author describes interactions, setting and personal feelings of the subjects.

Examine one interaction between cognition and physiology in terms of behavior. Evaluate two relevant studies. One of the most famous case studies of amnesia in the history is HM who was suffering from epileptic seizures and had a surgery when he was only nine years old that removed 2/3 of his hippocampus, medial temporal lobes, parahippocampal gyrus and amygdala. The operation was successful in its primary goal of controlling his epilespsy but as a result of the operation he suffered from severe anterograde amnesia.

After the operation, he could not commit new events to long-term memory. He could remember events from before the operation for the rest of his life. His working memory and procedural memory were intact. After the operation, he could continue to complete tasks that require recall from the short-term memory and that involved procedural memory but could not make use of long-term episodic memory after the operation. After the operation, he lost his declarative memory (semantic and episodic). Because of the removal of these parts of brain, he might face these problems.

One that might be he couldn’t encode the information or he could do that but he couldn’t retrieve it or he could do them but could not store them in his memory. had brain infection -herpes encephalitic- affecting the parts that are concentrated on memory. MRI scanning shows damage to the hippocampus and some of the frontal regions. His ability to perceive what he saw and heard was unimpaired. But he did not seem to be able to retain any impression of anything for more than a few blink. In he did blink, his eyelids parted to reveal a new scene.

In Clive’s case, the virus damaged his brain. It damaged the hippocampus, which play a major role in the handling of long-term memory formation. Additionally he sustained marginal damage to the temporal and frontal lobes. The former houses the amygdala, a component implicated in the control of emotions and associated memories. Clive developed a profound case of total amnesia as a result of his illness. Because the part of the brain required to transfer memories from the working to the long term area in damaged.

He is unable to encode new memories. He only remembers a little part of his life before. He still knows how to play piano, which is because his cerebellum responsible for the maintenance of procedural is not damaged. The fact that he could no longer remember anything and was not aware, tells us that the hippocampus and the temporal and frontal lobes are the bits responsible for LTM’s and STM’s formation and recall. In both cases, the hippocampus was damaged, and so they both had problems with their long-term memory.

In HM’s case only two thirds of the hippocampus was removed while in Clive’s case most of it was destroyed. As a result both had very severe amnesia and because of that we can conclude that hippocampus is the part of the brain responsible for forming/retrieving or storing the LTM. This is an example of the link between cognition and physiology of the brain. However, certain exceptions make this theory a lot more complex. For example HM had remembered JFK’s assassination and both could still learn new skills.

In Clive’s case, the fact that he could still emotionally remember his wife does not fit into the former explanation. However, the researches that were done consistently for these two people are reliable, giving us the opportunity to generalize such hypothesis on the cognitive part of the brain. For example, Brenda Milner, who studied HM following his surgery till his death, is a very well-known researcher and in her reports she has clearly mentioned HM’s past and present conditions.

Since she is known and experienced, her reports are likely to be true and not exaggerated. And because of that we believe it to be dependable and creditable as well as following a data triangulation. Milner hasn’t had any brain illnesses in her life, so we can easily decide that her research was in no way influence by her own disabilities. On the other hand she has not checked and re-checked her research results, trying to find fault in them, since HM’s case is a very unique case in the world.

And the fact that HM was old at the time when most of her research were conducted, we could argue that his memory loss was due to old age. Another fault in her research is its inaccuracies, an example of such inaccuracy is when HM remembered John F. Kennedy’s assassination. Based on these findings we can assume that her research is strong enough for us to be able to generalize its effects. That is why recently, scientists associate hippocampus and amygdala with memory formation and storage.

 Provide a brief description for each of the following functions:  Basal ganglia Controls cognition and movement coordination as well as voluntary movement. It is also a component of the corpus striatum and it consists of the subthalamic nucleus and the substantial nigra . There is a thick band of nerve fibers and these are called the corpus collosum. This is what divides the cerebrum into two hemispheres, a left and a right.

It creates communication between the left and the right sides by connecting them. It also transfers motor functions, sensory, and cognitive information between the two hemispheres (About. com, 2012).  The temporal lobe has three general function areas. These are the superior temporal gyrus, the inferior temporal cortex, and the medial temporal cortex. The superior temporal gyrus I where our hearing and language come in. The inferior temporal cortex helps us identify complex visual patterns.

The medial temporal cortex is what we rely on for memory (Pinel, 2009).  This is what is used to help us analyze the visual input which guides our behavior. Without it we may act differently than what we currently act because we wouldn’t see things the same way (Pinel, 2009). Each frontal lobe has two very unique functional areas which are the precentral gyrus and the frontal cortex which is right beside it which have motor capabilities. Frontal lobes are also one of the four main regions of the cerebral cortex.

This is where all your planning and decision making goes on and how you solve problems (About. com, 2012).  Cerebrum means cerebral hemispheres. When comparing the cerebrum to the brain stem it is known to be more complex and have an adaptive process such as your learning capabilities, your perception of things and your motivation towards doing things (Pinel, 2009).  The spinal cord combined with the brain is what makes up your central nervous system. It is a bundle of nervous tissue and supporting cells that extend from the medulla oblongata.

It starts at the occipital bone and goes down to the area between the first and second lumbar vertebrae (About. com, 2012).  The cerebellum is also known as the “little brain”. It is a large convoluted structure on the brain stem’s dorsal surface and plays an extremely important role in motor control (Pinel, 2009). It is possibly involved in other cognitive functions such as language and attention. a The medulla oblongata is a portion of the hindbrain that would control the functions we know as breathing, heart and blood vessel, digestion, sneezing, and swallowing.

The way that we move and the way the we hear are because neurons from the midbrain and the forebrain traveled through the medulla oblongata. The medulla helps the transference of messages between several areas of the brain and the spinal cord (About. com, 2012).  When ascending and descending tracts and part of the reticular formation happen this can cause a bulge or what is also known as a pons. IT is located on the brain stem’s ventral surface. The pons is one of the major divisions of the Metencephalon and the other is the cerebellum (Pinel, 2009).

Hippocampus is a huge component of the brain of a human. It plays an important role with short-term and long term memory and spatial navigation. There are two hippocampus in each human brain and it is closely associated with the cerebral cortex (About. com, 2012).  Amygdala If you were to look at the temporal lobe of the brain you would find an almond shaped mass of a nuclei located very deep. It is a limbic system structure and it is what we would know as what makes us cry and what makes us get motivated to exercise. It is also part of the brain that helps you process fear, anger and pleasure (About. om, 2012).  Pituitary gland It is a gland that dangles from the ventral surface of the brain. It exerts hormones and it’s literal meaning is snot gland, how lovely. It is known as the master gland because of how it directs other types of organs and endocrine glands. Those glands would consist of the adrenal glands which in turn can be used to suppress or amp up hormone production (Pinel, 2009).  Hypothalamus It is located right below the anterior thalamus and it has a huge role in the regulation of several motivated behaviors.

It works with the pituitary gland and is able to be connected to the nervous system and to the endocrine system. It synthesizes and secretes certain types of neurohormones. It controls your body temperature, how hungry you are, how thirsty you are, if you are sleepy or really really tired (Pinel, 2009).  The thalamus is located under the cerebral cortex in a dual lobed mass of grey matter. It is what is used to have sensory perception and how to regulate your motor functions. It also controls how much you sleep and how much you are awake .