ABSTRACT
The nervous system is the information highway of the body. The human nervous system is composed of approximately 10 neurons forming a network in which individual nerve cells use biochemical reactions to perform specialized functions. These are collecting information from sensory cells, relaying signals from one neuron to the next and delivering signals to muscles and other cells with instructions for action. The central nervous system is composed of the brain and the spinal cord. The neuron is the basic unit and messenger of the peripheral nervous system. Most neurons achieve their effects by releasing chemicals celled neurotransmitters sent to receiving cells such as postsynaptic neurons, muscle cells, and gland cells. If the aggregate input is greater than the axon hillock’s threshold value, the neuron fires and an output signal is transmitted down the axon. The mechanisms by which neurotransmitters elicit responses in presynaptic and postsynaptic neurons are diverse.
