Peripheral Nervous System

It connects the central nervous system with the sense organs, muscles and glands of the body and, includes the sensory and motor nerves.

The peripheral nervous system consists of two sub divisions:

  1. Somatic nervous system that conveys information from brain and spinal cord to skeletal muscles and regulates voluntary action.

  2. Autonomic nervous system which control the involuntary action of many internal organs, smooth muscles, heart muscles and glands.

Somatic Nervous System

This consists of two sets of nerves - the cranial nerves and the spinal nerves.

  • 12 pairs of cranial nerves emerge from the brain. For example, optic nerve (for eyes) and auditory nerve (for ears).

  • 31 pairs of spinal nerves emerge from the spinal cord.

Autonomic Nervous System

The autonomic nervous system (ANS) consists of a pair of chain of nerves and ganglia on either side of the backbone. This system controls the involuntary actions of the internal organs. There are two parts of the autonomic nervous system - Sympathetic and Parasympathetic.

The Sympathetic Nervous System (SNS) becomes more active during times of stress. It prepares the body for action. Its action during the stress response comprise the "fight-or-flight response" that is manifested largely under the influence of the hormone, adrenaline.

The Parasympathetic Nervous System executes actions that do not require immediate response, for example producing of saliva and tears, digestion, etc.