All multicellular animals contain elongated nerve cells, called neurons, collected together into parallel bundles called nerve trunks. Every nerve trunk contains thousands of neurons. It is clear that these control the movements of muscles (via motor nerves) and the conduction of information from the sense organs to the central nervous system (via sensory nerves). Each neuron has a cell body , called the neurocyton, 4 to 25 microns in diameter, containing a nucleus and cytoplasm much like that of other cells. The entire nervous activity is based on reflexes, the functional units of the nervous system.
there are two main services of our nervous system or also known as the two major divisions.
- The Central nervous system which consist of the brain and the spinal cord.
- The Peripheral nervous system which consist of all other neural elements.