ABSTRACT
The nervous system is a complex, sophisticated system that regulates and coordinates body activities. It has two major divisions
: central nervous system (CNS) and peripheral nervous system (PNS). The central nervous system consists of the brain and the spinal cord, while the peripheral nervous involves all the nerves that branch off from the spinal cord to the extremities. The fundamental cell of the brain is the neuron, which consists of a cell body, branch-like extensions off the cell body called dendrites, and at least one longer extension off the cell body called an axon. The dendrites conduct signals from their tips toward the neuron cell body whereas the axon carries message away from the cell body toward the terminal end of the axon. The neuron communicates with the other cells, such as effector cells, through the distal tips of the axon. Nerves are bundles of the axons from different neurons that carry signal in the same direction; nerves are essential intermediary connecting the brain to effector cells. Thus, if the nerves are severely injured, the signal between the cell body and the effector cells is interrupted, and neurons are unable to convey effective requests, such as a muscle movement.
