Module 1: Introduction to the Human Nervous System

Major Subdivisions of the Nervous System

The human nervous system can be considered in three major subdivisions:
a. The central nervous system (CNS) which consists of the brain and the spinal cord.
b. The peripheral nervous system (PNS) which consists of the nerves which go from the CNS to the periphery of the body.
c. The autonomic nervous system (ANS) which is that portion of the nervous system concerned with commands for smooth muscle tissue, cardiac muscle tissue, and glands.

The Central Nervous System (CNS) consists of the brain and the spinal cord.

The Peripheral Nervous System (PNS) consists of the nerves which go from the central nervous system (CNS) to the periphery of the body.

The afferent division of the peripheral nervous system consists of the nerve fibers which project to the central nervous system.

The efferent division of the peripheral nervous system consists of those nerve fibers which project out of the central nervous system.

The somatic sensory nervous system carries signals from the muscles to the CNS.

The visceral sensory nervous system carries signals from the visceral organs to the CNS.

The ANS is organised into two major subdivisions - the sympathetic and the parasympathetic nervous systems.

The neurons of the sympathetic nervous system originate in the thoracic and lumbar regions of the spinal cord.

It is also known as the thoraco-lumbar outflow.

Some of the neurons of the parasympathetic nervous system originate in nuclei of the brainstem.