Structure:
The peripheral nervous system is the extension from the brain
and the spinal cord, reaching the somatic and
the visceral organs. It is made up of the cranial
nerves, the sensory nerves, the
motor nerves, and the autonomic
nerves. The basic unit of nerves is the nerve cell, the neuron.
These are made up of a cell body, called a perikaryon, and nerve
fibers of two types, axons and dendrites.
Function:
The cranial nerves respond to the stimuli from the head, especially the
senses of vision,smell, hearing,
and taste. The sensory nerves return
to the CNS the stimuli from the environment, especially the skin,
sending them to the sensory cortex of the cerebrum.
The motor nerves carry from the cerebrum and the cerebellum,
the nerve impulses that cause muscles to contract,
stay tight for posture, or to relax. The autonomic nerves carry signals
to the brain and away from the brain, especially the brainstem. These signals
control the breathing, the heart
rate, the temperature, the emotions for making tears,
the belly cramps from fear, the
need to urinate, etc.
