Peripheral Nervous System

The nervous system is a controlling system of the body and is composed of nerve cells.The nervous system is further classified into the central and the peripheral nervous system.

The brain and spinal cord collectively form the central nervous system and the network of nerves found outside of the brain and the spinal cord is called as the peripheral nervous system.

The nerves fibers are of two types – afferent fibers and efferent fibers. The afferent nerve fibers are responsible for transmission of impulses from the tissues to the central nervous system while the efferent nerve fibers are responsible for transmission of impulses from central nervous system to the concerned tissues or organs. Let us study the peripheral nervous system in details.

Peripheral Nervous System

Nervous system

Peripheral nervous system

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

Somatic nervous system– The main function of this system is to transfer impulses from CNS to skeletal muscles. It consists of cranial nerves and spinal nerves. Cranial nerves emerge from the brain and there are twelve pairs of cranial nerves. Some of the examples may be the sensory nerves like optic, olfactory, etc. Spinal nerves have their point of emergence as the spinal cords. There are thirty-one pairs of spinal nerves. They emerge from the spinal cords into dorsal and ventral roots. At the junction of these two roots, the sensory fibers continue into the dorsal root and the motor fibers into the ventral root.

The autonomic nervous system relays impulses from the central nervous system to the involuntary organs and smooth muscles of the body. It again has two parts – sympathetic and parasympathetic. A sympathetic nervous system consists of nerves arising from spinal cord between the neck and waist region.It prepares the body for violent actions against abnormal conditions and is generally stimulated by adrenaline. The parasympathetic nervous system is located anteriorly in the head and neck and posteriorly in the sacral region. It is mainly involved in re-establishment of normal conditions when violent action is over.

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Practise This Question

Which organ is used by a frog for breathing under water?