School of Social Work The Nervous System Undergraduate researchers: Kate Decoste, Lauren Degrange, Liz Miller, Sean Mortenson, Batool Qweider, and Kaylie Reese (2009). Co-edited by Nancy D. Bergerson (2010). 1 The nervous system controls the body's sensations. It also controls the body's conscious and unconscious operations. The nervous system has two main parts: central nervous system peripheral nervous system The central nervous system is the brain and spinal cord. The peripheral nervous system is the rest of the nervous system outside of the brain and spinal cord. The Central Nervous System First, we will look at the brain. A human brain weighs approximately 1.36 kg (3 lbs). It is made of millions of neuron cells. A neuron cell looks like a tree trunk with branches and roots at the ends. These branches and roots are called dendrites. Dendrites catch and send messages at very high speed. Figure 1 shows the structure of a neuron cell. 1 The Nervous System educational unit was researched and compiled by the undergraduate researchers as part of the Fall 2009 course requirements for SWK 380 - The Biological Person and the Environment, offered through the University of Maine School of Social Work (Professor Stephen F. Gilson, Ph.D.). The unit was edited by undergraduate, Nancy D. Bergerson, under the supervision of Stephen F. Gilson, Ph.D., Coordinator and Professor of Interdisciplinary Disability Studies and Professor of Social Work; and Elizabeth DePoy, Ph.D., Professor of Interdisciplinary Disability Studies and Professor of Social Work; in partial fulfillment of her Disability Studies Internship during the Spring 2010 semester. Important! Each educational unit contains words that are defined in the Know Your Body Glossary. Please remember to include the Glossary when downloading the educational unit(s) in PDF format.
2 of 10 Figure 1. Structure of a Neuron Cell. Ramon, R. S. (n.d.). What are Neurons and how do they Communicate? HubPages. http://hubpages.com/hub/neurons-and-neurotransmitters The brain has two halves. Each half controls the opposite side of the body. The two halves of the brain communicate through the corpus callosum, a bundle of nerve fibers connecting the two sides together. Figure 2 shows the two halves (hemispheres) of the brain. Figure 2. Hemispheres of the brain. Inside the human brain. (n.d.). U.S. National Institute of Health National Institute on Aging. http://www.nia.nih.gov/alzheimers/publications/unraveling/part1/inside
3 of 10 Figure 2 also shows the outer layer of the brain called the cerebral cortex. The name "cortex" comes from the Latin word for "bark", like the bark of a tree. The cerebral cortex has four areas called lobes. These four areas process what we see, hear, taste, touch and smell. These are the four lobes of the brain: Occipital Temporal Parietal Frontal You can see the lobes of the brain in Figure 3. Figure 3. The Four Lobes of the Brain. Diagram of the basic parts of the brain. (n.d.). Brain Health & Puzzles. http://www.brainhealthandpuzzles.com/diagram_of_brain.html The thalamus, hypothalamus, and pituitary gland are located in the brain. You can find out more about these glands in the endocrine system. Another important part of the brain is the cerebellum. It is located at the back of the brain. The cerebellum controls movement and balance.
4 of 10 Figure 4. The Brain Stem. Johnson, Gordon S. Jr. (n.d.). About Brain Injury: A Guide to Brain Anatomy. http://www.waiting.com/brainstem.html The brain stem connects the brain to the spinal cord. Figure 4 is a drawing of the brain stem. The spinal cord is as big around as a human finger. It is made of millions of nerve fibers that send electrical information between the brain and the body. Nerves called spinal nerves or nerve roots come off the spinal cord through holes in the vertebrae. There are 31 pairs of spinal nerves. The spinal nerves and what they control are shown in Figure 5.
5 of 10 Figure 5. Spinal Nerves. Anatomy of the Spinal Cord. (n.d.). Information on Spinal Cord Injuries http://www.scirecovery.org/anatomy.html Three layers of tissue protect the central nervous system. They are meninges. Clear liquid, called cerebrospinal fluid, surrounds the brain and spinal cord. This liquid cushions and protects them from injury. The Peripheral Nervous System The peripheral nervous system connects the brain and spinal cord to the rest of the body with cranial and spinal nerves. Nerves send information about what we see, hear, feel, taste or touch. If you touch something hot, your nerves send information from the hand to your brain. The brain reads the information and sends a message back to your hand to pull away to prevent injury. The peripheral nervous system has two parts: the somatic nervous system the autonomic nervous system The somatic nervous system controls the skeletal muscles. It also keeps the body in touch with its surroundings through the senses.
6 of 10 The autonomic nervous system is involuntary. If controls the heart and smooth muscles. The autonomic nervous system has two parts seen in Figure 6: sympathetic nervous system parasympathetic nervous system Figure 6. The Autonomic Nervous System. Autonomic nervous system. (n.d.). Autonomic Nervous System. http://users.rcn.com/jkimball.ma.ultranet/biologypages/a/autonomic.gif The sympathetic nervous system reacts to threats with a fight or flight response. Four types of events usually cause this response: Emergency Excitement Embarrassment Exercise In these situations, the sympathetic nervous system slows body functions not needed at that moment. It directs the body's energy to the fight or flight response.
7 of 10 The parasympathetic nervous system balances the sympathetic nervous system. Once a crisis has passed, it stops the stress response started by the sympathetic nervous system. Keeping the Nervous System Healthy Some disorders are built-in to the nervous system, but healthy habits can prevent many diseases. Do not smoke. Eat fresh fruits and vegetables. Eat and drink dairy products. Eat foods rich in B vitamins. They are important to the nervous system. Drink alcohol in moderation. Get regular exercise. Practice safe sex. Diseases of the Nervous System Below is a list of common diseases of the nervous system: Alzheimer s disease causes memory loss and loss of bodily functions. It is a deterioration of brain matter and usually occurs in older adults. It is also called "senile dementia". Amyotrophic Lateral Sclerosis, also called "Lou Gehrig s Disease", destroys motor neurons causing loss of muscle control. Its cause is unknown. Bell's Palsy is facial paralysis caused by damage to a nerve, usually on one side of the face. Cerebral concussion is due to a hit to the head or sudden jarring movement of the brain against the skull. It can cause loss of consciousness, headache, dizziness, vomiting, possible paralysis and impaired brain function. Cerebral palsy is a form of paralysis caused by damage to areas of the brain, before birth or during infancy. People with cerebral palsy cannot fully control their movements.
8 of 10 Encephalitis is an inflammation of the brain. It is caused by a viral or bacterial infection. During the inflammation, the brain becomes swollen. Symptoms are fever and headache. It can become very severe. Epidural hematoma is bleeding between the cranium (skull) and the brain's covering, called the dura mater. A blow to the head causes most epidural hematomas. Epilepsy causes neurons in the brain send messages abnormally. This can cause loss of attention, sleepiness or severe spasms with loss of consciousness. Gullain-Barre Syndrome causes the body s immune system to attack the peripheral nervous system. Symptoms include tingling in the legs or arms and loss of muscle function. The cause is unknown. Herpes Zoster, also called "shingles, is a skin rash caused by the same virus that causes chickenpox. After a person has chickenpox, this virus continues to live in the nervous system. Stress can cause it to become active again. The rash usually follows the path of one nerve and is very painful. Hydrocephalus is a build-up of cerebrospinal fluid around the brain. This puts pressure on the brain and enlarges the head. It can cause convulsions, mental disability, or death. Injuries of the spinal cord can result from wounds, fractures, injuries to the spinal column, or tumors. Meningitis is usually bacterial, but can also be viral. It comes on rapidly and, if not treated, can quickly lead to coma and death. Early symptoms are like the flu. Multi-infarct dementia is brain damage due to a series of small strokes. Multiple Sclerosis (MS) causes the myelin sheath surrounding the axons to destroy itself. This is the most common central nervous system disease of young adults in the U.S. Parkinson's Disease causes tremors, problems moving limbs and joints, slow movement and impaired balance. Its cause is unknown.
9 of 10 Peripheral neuritis (or neuropathy) is the breakdown of nerves that supply the far areas of the body, causing pain and paralysis. Poliomyelitis affects mostly children. It spreads through direct contact through mucous, phlegm, feces, or contact with food and water contaminated by feces of an infected person. When it invades the nervous system, it can cause paralysis or death. Stroke or CVA (cerebrovascular accident) is caused by blockage of the blood supply to the brain. This causes brain cells to die. Strokes can cause aphasia, the loss of the ability to speak, write or understand. They can also result in partial or full paralysis. Severe strokes can cause death. Subdural hematoma is bleeding between the dura mater and the brain. A blow to the head or a burst blood vessel within the brain can cause a subdural hematoma. Case Study of Diseases of the Nervous System Susan is 30 years old and has been healthy her entire life. She began to have muscle spasms and pain in her legs. She also began feeling tired and depressed. Susan visited her doctor and learned she has multiple sclerosis. She started medication to control and slow her symptoms. Currently, there is no cure. Multiple sclerosis damages the coating around nerve cells. It causes communication between nerve cells to slow down or stop. Susan will undergo physical therapy to help her body cope with her disease. Susan will also need to decrease stress and increase her rest because stress worsens the symptoms of multiple sclerosis. References Anatomy of the Spinal Cord. (n.d.). Information on Spinal Cord Injuries. Retrieved February 28, 2010 http://www.scirecovery.org/anatomy.html Autonomic nervous system. (n.d.). Autonomic Nervous System. Retrieved November 18, 2009 from http://users.rcn.com/jkimball.ma.ultranet/biologypages/a/autonomic.gif Johnson, Gordon S. Jr. (n.d.). About Brain Injury: A Guide to Brain Anatomy. Retrieved January 25, 2010 from http://www.waiting.com/brainstem.html Cohen, B. J. (2008). Memmler's The Human Body in Health and Disease. Philadelphia: Lippincott Williams & Wilkins.
10 of 10 Diagram of the basic parts of the brain. (n.d.). Brain Health & Puzzles. Retrieved November 18, 2009 from http://www.brainhealthandpuzzles.com/diagram_of_brain.html Inside the human brain. (n.d.). U.S. National Institute of Health National Institute on Aging. Retrieved January 17, 2010 from http://www.nia.nih.gov/alzheimers/publications/unraveling/part1/inside National Institute of Neurological Disorders and Stroke. (n.d.). In National Institute of Neurological Disorders and Stroke. Retrieved November 18, 2009 from http://www.ninds.nih.gov/ The parts of the brain. (n.d.). Cancer Help UK. Retrieved January 17, 2010 from http://www.cancerhelp.org.uk/type/brain-tumour/about/the-brain#parts1 Ramon, R. S. (n.d.). What are Neurons and how do they Communicate? HubPages. Retrieved March 1, 2010, from http://hubpages.com/hub/neurons-andneurotransmitters