The autonomic nervous system contains the sympathetic and parasympathetic nervous system is a part of the central nervous system. The autonomous nervous system controls the vital organs. It contains the stomach, intestines, heart and the glands. Most of the actions performed by the visceral organs are involuntary. They have an automated function. These actions are carried out subconsciously in our body like breathing, digesting, and the beating of heart.
Both the divisions of the autonomic system work without making a conscious effort. The sympathetic and parasympathetic nervous system is connected through nerves that carry out several signals. The autonomous nervous system regulates the nerve signal output and homeostasis of the body. The cranial nerve is the main nerve of the autonomous nervous system.
The sympathetic nervous system causes the flight or fight syndrome n the body. This is activated when we go through stressful circumstances. The sympathetic nervous system activates the adrenal gland to cause such a reaction. It is also called the sympathetic- adrenal response. The ganglion fibers that start in the sympathetic nervous system terminate in the adrenal glands. The response created by the sympathetic nervous system also controls the cardiac responses during stress.
Doctors look at SNS as an automatic regulation system; it does not need the help of consciousness to work. Scientists believe that the sympathetic nervous system was there in the early organisms for survival. For instance, when we wake up in the morning, the body restores its automatic functions without us causing it. They prepare themselves for the actions to come.
The parasympathetic nervous system is also a division of the autonomic nervous system. It is also called as the feed and breed or rest and digest system. The PNS relaxes the body and conserved energy, so it slows down the heart rate, causes the intestine to work harder and also increases the glands activity while slowing down the muscle reactions.
When the sympathetic nervous system causes flight or fight syndrome, the parasympathetic nervous system will cause a relaxation reaction. This action by the PNS equalizes the effects caused by the sympathetic nervous system. For instance, the sympathetic nervous system causes an increase in heart rate, while the PNS relaxes the hart rate. However, they do not take place simultaneously. The responses caused by both these systems are very important for our survival. However, too much of these responses are not good for us.
Wiki Books: Human Physiology - The Nervous System - The Sympathetic and Parasympathetic Systems
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