The nervous system in our body is comprised of the central and peripheral nervous systems. The peripheral nervous system is subdivided in to somatic and autonomic nervous systems. The former is related to control of voluntary movements, while the latter is associated with the control of involuntary activities.
The autonomic nervous system regulates the basic processes of the organs required for the normal functioning of the body. It is not related to voluntary control while certain activities like fear, emotional stress, alterations in the sleep and wakefulness cycles and sexual arousal change the extent of autonomic activity.
This system innervates three types of tissues in the body; smooth muscles, cardiac muscle and glands. The autonomic nervous system also encompasses the function of relaying visceral sensory related information to the central nervous system and further processes it in such a manner that certain changes in the activities of autonomic system’s motor outflows like controlling the heart, visceral organs and blood vessels results. Certain hormones which are associated with energy metabolism or functions related to the heart also get released by stimulation through these nerves. Thus the entire functioning of the body internally is maintained in a state of equilibrium called homeostasis.
The autonomic nervous system is further sub-divided as sympathetic and parasympathetic nervous systems. Both these systems have two sets of neurons connected for the outflow of signals while they actually function in an antagonistic manner. The preganglionic neurons start from the spinal cord and the second set referred to as ganglionic or postganglionic neurons lie in the cluster of nerves outside the central nervous system called as autonomic ganglia.
Parasympathetic ganglia lie either close to or inside the tissues or organs which the neurons innervate. Sympathetic ganglia are located away from the target organs. Both these systems have sensory fibers which are used to transfer information regarding the functioning of the target organs to the central nervous system.
Autonomic system has a third category called enteric system, which consists of neurons embedded in the walls of the entire digestive tract from the esophagus to the large intestine. This controls the secretions in the digestive system and gastrointestinal motility.
The autonomic nervous system regulates involuntary processes in our body like breathing, perspiration, heart rate and blinking. The functioning of the body involuntarily when it is in a state of rest and not alert is controlled by parasympathetic nervous system. Some examples are digestion, salivation and arousal.
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