PERIPHERAL NERVOUS SYSTEM

PERIPHERAL NERVOUS  SYSTEM

(PNS)

This comprises of all those neurons which lie outside the brain and the spinal cord and connect these two with receptors, effectors and gland. It is divided into two parts i.e. somatic and autonomic nervous system.

 

      I.            Somatic Nervous System : The somatic system is made up of two different types of neurons are (sensory neurons), which transmit messages to the central nervous system, and (motor neurons), which relay information from the central nervous system to other areas of the body.

·      Cranial Nerves : Cranial nerves are the nerves that emerge directly from the brain. It originate from the bony skull and are found in pairs of Twelve nerves.  These are motor, sensory nerves.

·      Spinal Nerves : A spinal nerve is a mixed nerve, which carries motor, sensory and autonomic signals between the spinal cord and the body and there are 31 pairs and are divided into five parts.

 

   II.            Autonomic Nervous System : The autonomic nervous system plays an important role in homeostasis, which maintain in balance internal processes like body temperature, heart rate and blood pressure. Autonomic nervous system is further subdivided into – Sympathetic nervous system  and  Parasympathetic nervous system.

·      Sympathetic Nervous System : Its is located in the lumbar region of spinal cord. It prepares our body for emergency situations e.g. when faced with danger it activates  adrenal gland and pancreas thereby increasing the quantity of blood sugar level in blood and also increases the rate of metabolism. All these changes in the body give us extra energy to meet the emergency situation.

 

·      Parasympathetic Nervous System : It functions to restore our bodily processes to normal. In other words it is the opposite of sympathetic system. It lowers metabolic rate, heart rate and quantity of blood sugar in the blood.

Although the two systems are opposite they tend to act in a coordinated manner. For Ex:  In situation of fear or anger adrenal gland, pancreas are activated by the sympathetic system to generate more energy. The parasympathetic system suspends digestive activity and other functional systems so that energy feed from these is available for us to meet the emergency situation.