NERVOUS SYSTEM

What is Nervous System?
The central nervous system—the brain and spinal cord—receives information from all over the body. This information takes the form of electrical impulses that are transmitted along a nerve network—the peripheral nervous system-which branches off the central nervous system. The brain then sends out instructions to internal organs, muscles, glands, and tissues throughout the body via the peripheral nervous system. In terms of function, the parts of the nervous system consisting of nerves that control the muscles involved in voluntary actions are known as the somatic nervous system. Nerves concerned with the unconscious control of bodily functions such as digestion, gland secretions, and temperature regulation are part of the autonomic nervous system.
A nerve is made up of strings of nerve cells, or neurons, which are the basic units of the nervous system. Some nerves carry instructions from the brain or spinal cord to muscles, glands, or other tissues throughout the body. Others carry information to the brain from sensory receptors, sensory organs such as the eyes and ears, and internal organs. Each nerve cell has parts that receive electrical messages from other nerve cells, and parts that transmit messages to nerve cells or other tissues. The cell bodies of neurons make up the gray matter of the brain and spinal cord, while the long nerve fibers, or axons, make up the white matter of the central nervous system.
All but the smallest nerve fibers are insulated and protected by a fatty substance called myelin, which also helps to conduct nerve impulses quickly along the fibers. Multiple sclerosis is believed to occur because the myelin becomes damaged in some way. The brain and spinal column are protected by delicate membranes called meninges.

MULTIPLE SCLEROSIS

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