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Preksha Dhyana:
branching vagus nerve supplies various structures of the trunk.
31 Pairs of spinal nerves, each containing thousands of nerve-fibres, branch out from the spinal cord. They ennervate the entire trunk and limbs (extremities). Each spinal nerve is a mixed nerve containing both sensory and motor fibres.
Deep cuts and crushing blows can damage nerves resulting in a loss of sensation or paralysis. Pressing on a. nerve for more than 20 minutes makes the body-part served by it to go to sleep, i.e. it produces temporary anasthesia. Autonomic Nervous System
Autonomic nervous system is also known as 'visceral motor system'. The motor-nerves involved in the control and coordination of inner working of our body form a division of the peripheral nervous system called the 'autonomic nervous system'. A high degree of orchestration of vital organs-the heart, the lungs, the glands is accomplished through intricate sequences of feed-back circuits with interacting nervous and endocrine controls. Appropriate actions are taken automatically and independently of the conscious brain through autonomic nervous system. Autonomic nerves are motor nerves carrying impulses to smooth muscles of the visceral organs, heart and glands. The circuits are completed by association with sensory nerves of the P.N.S. and control-centres of C.N.S.
The autonomic nervous system has two separate divisions: (i) parasympatbetic, and (ii) sympathetic, each pro. viding for a particular type of function.
The para-sympathetic division is concerned with keeping the body systems running smoothly day in and day out and conserving and restoring body-resources, e.g. it causes relaxation of the smooth muscle of the walls of blood vessels thus dilating them and protecting the heart from over-exerting itself. It promotes a harmonious course of the digestive processes. In short, it is the 'repose and repair' mechanism of the body. Structurally and functionally, it is more advanced of the two divisions.
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