NERVOUS SYSTEM -the network of nerve cells and fibers that transmits nerve impulses between parts of the body.

TYPES -In vertebrate species it consists of two main parts, the central nervous system (CNS)and the peripheralnervous system (PNS). The CNS contains the brain and spinal cord. The PNS consists mainly of nerves, which are enclosed bundles of the long fibers or axons, that connect the CNS to every other part of the body.

PARTS AND FUNCTIONS -The cells that make up the nervous system are called neurons.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. When you think, neurons in your brain are working. 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.

NERVE CELL - See neuron. The body of a neuron without its axon and dendrites.

Nerve impulse- a signal transmitted along a nerve fiber. It consists of a wave of electrical depolarization the reverses the potential difference across the nerve cell membranes.