The Nervous System is the body's information gatherer, storage center and control system. Its overall function is to collect information about the external conditions in relation to the body's internal state, to analyze this information, and to initiate appropriate responses to satisfy certain needs.
The cells that make up the nervous system are
called neurons. Long, stringy neurons are perfect for
carrying the electrical messages that are the "language"
of the nervous system.
The brain is the command center of your entire body. The brain is the body's main information center. It is made of billions of neurons. The brain helps the body respond to the information it receives from the senses. The brain also processes thoughts.
The spinal cord is a tube of neurons that runs up the spine and attaches to the brain stem. Information from nerves that branch out to the rest of the body goes to the spinal cord. Some messages are processed by the spinal cord but most information is sent on to the brain.
A Neuron consists of THREE MAIN PARTS:
A. CELL BODY - The largest part, contains the nucleus and much of the cytoplasm (area between the nucleus and the cell membrane), most of the metabolic activity of the cell,
B. DENDRITES - Short branch extensions spreading out from the cell body. Dendrites Receive STIMULUS (Action Potentials) and carry IMPULSES from the ENVIRONMENT or from other NEURONS AND CARRY THEM TOWARD THE CELL BODY.
C. AXON - A Long fiber that CARRIES IMPULSES AWAY FROM THE CELL BODY. Each neuron has only ONE AXON. The Axon Ends in a series of small swellings called AXON TERMINALS.
The CENTRAL NERVOUS SYSTEM serves as the CONTROL CENTER of the body. The Central Nervous System consists of the BRAIN and SPINAL CORD.
The Central Nervous System relays messages, processes information, and compares and analyzes information. The Central Nervous systems DOES NOT come in contact with the Environment. This job is left to the other major division of the nervous system - The Peripheral Nervous System.
All of the nervous system outside the spinal cord and brain is known as the PERIPHERAL NERVOUS SYSTEM.
The peripheral nervous system can be divided into two divisions:
A. THE SENSORY...