Endocrine System

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The Peripheral Nervous System

2.4     The 31 pairs of spinal nerves as well as all the other nerves and nerve cells outside of the central nervous system make up the third part of the nervous system. This system carries nerve impulses to and from the body’s sensory cells and the central nervous system. The central nervous system analyses the information it receives from the peripheral nervous system and responds to it. The motor neurons of the peripheral nervous system carry out the instructions received from the central nervous system. It acts as a switchboard that controls and coordinates the activities of the entire nervous system.

 

The Nervous Tissue

2.5     The tissue of the nervous system is composed of two basic types of cells, neurons and glia (glial cells). A neuron consists of a cell body; dendrites, branched structures that conduct impulses to the cell body; and an axon, a long fibre that transmits impulses away from the body. There are three types of neurons. Sensory neurons send signals from the sense organs to the spinal cord and the brain. Motor neurons send signals from the brain and the spinal cord to the body’s muscles. Association neurons link sensory neurons to motor neurons. Glial cells help support and nourish neurons and account for approximately one-half of the volume of the nervous tissue. There are four types of glial cells, each with a different function.