Peripheral Nervous System

The nervous system is a master system that controls the functions of all different systems of a human body. It is made up of cells called neurons that generate and conduct impulses (messages) between various parts of the body. It consists of the brain, the spinal cord and nerves. While the brain and the spinal cord form the Central Nervous System (CNS), the Peripheral Nervous System includes all the nerves outside the CNS. The brain is protected by the skull and the spinal cord is enclosed within the bony spinal column. However, the Peripheral Nervous System does not have any such protective covering and hence is prone to mechanical injuries.

Components
On the basis of location of the nerves, the Peripheral Nervous System consists of the following nerves:

• 31 pairs of Spinal Nerves that connects the spinal cord with the rest of the body.
• 12 pairs of Cranial Nerves that connect the brain with the vital organs of the body.

On the basis of the functions of the nerves, the Peripheral Nervous System consists of the following nerves:

• Somatic Nerves which carry sensory information from the skin and muscle, and motor commands to the skeletal muscles.
• The Autonomic nerves which carry signals between the CNS and smooth muscles, glands, cardiac muscles and internal organs.

Functions
The nerves of peripheral nervous system connect the CNS to muscles, glands, blood vessels and all the organs of the body including the sense organs. The function of this nervous system is to carry messages from the brain to all the other parts of the body, and back from these parts to the brain and the spinal cord.

Divisions
The peripheral nervous system is divided into the somatic nervous system and the autonomic nervous system.

Somatic Nervous System
The somatic nervous system controls voluntary movements of our body and helps us feel through all our senses. The nerves of the somatic nervous system connect the brain and the spinal cord, to the skeletal muscles and the external receptors. Hence, this system helps us to move our body around, and feel the touch, smell, sight, taste and sound.

Autonomic Nervous System
The autonomic nervous system is also known as the involuntary nervous system, as it controls all the involuntary actions of the body. These nerves connect the CNS to the cardiac muscles, internal organs and the glands. The autonomic nervous system can be further sub-divided in to:

• Sympathetic Nervous System: The sympathetic nervous system is also referred to as the 'flight or fight system', as it prepares our body for emergencies. It results in increased heartbeat, high blood pressure and brings about other changes by the release of adrenaline, that prepares us to face danger or stress.
• Parasympathetic Nervous System: The Parasympathetic Nervous System on the other hand has just the opposite effect. It helps in calming and relaxing the body and ensures proper functioning of the digestive system. Hence, it is also known as the 'Rest and Digest System'. It dilates the pupil, restores normal blood pressure and heartbeat.

Although diseases or injuries to the CNS can have more serious effects than the peripheral nervous system when affected, trauma or infection of the peripheral nervous system can be manifested in the form of weakness, loss of control over limbs, slowly progressing sensory loss and weak bowels. Any disorder related to the nervous system should be referred to a neurologist for proper diagnosis as, proper functioning of the CNS or the Peripheral Nervous System is important for a healthy life.