|
|
|
|
| 11/22/09 |
 |
|
 |
|
Fowler & Associates - Medical Demonstrative Evidence Medical Reference Library |
| Print this article |
|
|
Brain Physiology
Brain Physiology
The brain and the rest of the nervous system are composed of many different types of cells, but the primary functional unit is a cell called the neuron. All sensations, movements, thoughts, memories, and feelings are the result of signals that pass through neurons.
Neurons consist of three parts.The cell body contains the nucleus, where most of the molecules that the neuron needs to survive and function are manufactured. Dendrites extend out from the cell body like the branches of a tree and receive messages from other nerve cells. Signals then pass from the dendrites through the cell body and may travel away from the cell body down an axon to another neuron, a muscle cell, or cells in some other organ.
The neuron is usually surrounded by many support cells. Some types of cells wrap around the axon to form an insulating sheath. This sheath can include a fatty molecule called myelin, which provides insulation for the axon and helps nerve signals travel faster and farther. Axons may be very short, such as those that carry signals from one cell in the cortex to another cell less than a hairOoOhms width away. Or axons may be very long, such as those that carry messages from the brain all the way down the spinal cord.
Scientists have learned a great deal about neurons by studying the synapse, the place where a signal passes from the neuron to another cell. When the signal reaches the end of the axon it stimulates tiny sacs. These sacs release chemicals known as neurotransmitters into the synapse. The neurotransmitters cross the synapse and attach to receptors on the neighboring cell. These receptors can change the properties of the receiving cell. If the receiving cell is also a neuron, the signal can continue the transmission to the next cell.
Some Key Neurotransmitters at Work
Acetylcholine is called an excitatory neurotransmitter because it generally makes cells more excitable. It governs muscle contractions and causes glands to secrete hormones. AlzheimerOoOhms disease, which initially affects memory formation, is associated with a shortage of acetylcholine.
GABA (gamma-aminobutyric acid) is called an inhibitory neurotransmitter because it tends to make cells less excitable. It helps control muscle activity and is an important part of the visual system. Drugs that increase GABA levels in the brain are used to treat epileptic seizures and tremors in patients with HuntingtonOoOhms disease.
Serotonin is an inhibitory neurotransmitter that constricts blood vessels and brings on sleep. It is also involved in temperature regulation. Dopamine is an inhibitory neurotransmitter involved in mood and the control of complex movements. The loss of dopamine activity in some portions of the brain leads to the muscular rigidity of ParkinsonOoOhms disease. Many medications used to treat behavioral disorders work by modifying the action of dopamine in the brain.
 Neurological Disorders
When the brain is healthy it functions quickly and automatically. But when problems occur, the results can be devastating. Some 50 million people in this countryOoOhmone in fiveOoOhmsuffer from damage to the nervous system. The NINDS supports research on more than 600 neurological diseases. Some of the major types of disorders include: neurogenetic diseases (such as HuntingtonOoOhms disease and muscular dystrophy), developmental disorders (such as cerebral palsy), degenerative diseases of adult life (such as ParkinsonOoOhms disease and AlzheimerOoOhms disease), metabolic diseases (such as GaucherOoOhms disease), cerebrovascular diseases (such as stroke and vascular dementia), trauma (such as spinal cord and head injury), convulsive disorders (such as epilepsy), infectious diseases (such as AIDS dementia), and brain tumors.
Source: National Institute of Neurological Disorders and Stroke
National Institutes of Health
Reviewed July 3, 2003
Medical/Legal Disclaimer
Copyright © 2003 Nucleus Medical Art, Inc. All Rights Reserved. |
|
|
 |
|
 |
| Related Medical Demonstrative Evidence - click thumbnail to review. |
|
|
|
|
|
| |
|
|
|
|
| |
|
|
|
|
| |
|
|
|
|
| |
|
|
|
|
|
How do I find a personal injury lawyer in my local area?
Find a personal injury lawyer in your local area using LEGALpointer™, a
national directory of U.S. attorneys specializing in personal injury,
medical malpractice, workers' compensation, medical product liability and
other medical legal issues. Or, click on one of the following to see
attorneys in your area:
Alabama (AL),
Alaska (AK),
Arizona (AZ),
Arkansas (AR),
California (CA),
Colorado (CO),
Connecticut (CT),
Delaware (DE),
Washington D.C. (DC),
Florida (FL),
Georgia (GA),
Hawaii (HI),
Idaho (ID),
Illinois (IL),
Indiana (IN),
Iowa (IA),
Kansas (KS),
Kentucky (KY),
Louisiana (LA),
Maine (ME),
Maryland (MD),
Massachussets (MA),
Michigan (MI),
(MN),
Mississippi (MS),
(MO),
Montana (MT),
North Carolina (NC),
North Dakota (ND),
Nebraska (NE),
Nevada (NV),
New Hampshire (NH),
New Jersey (NJ),
New Mexico (NM),
New York (NY),
Ohio (OH),
Oklahoma (OK),
Oregon (OR),
Pennsylvania (PA),
Puerto Rico (PR),
Rhode Island (RI),
South Carolina (SC),
South Dakota (SD),
Tennessee (TN),
Texas (TX),
Utah (UT),
Virginia (VA),
Virgin Islands (VI),
Vermont (VT),
Washington (WA),
West Virginia (WV),
Wisconsin (WI).
|
|
|
