Function Of The Sympathetic Nervous System

Function Of The Sympathetic Nervous System

The sympathetic nervous system is a division of the peripheral nervous system, which, in turn, is part of the nervous system. The nervous system in a body is subdivided into the peripheral and central nervous systems. The autonomic nervous system is one of the divisions of the PNS, or peripheral nervous system. It controls the unconscious actions of the body. The ANS, or autonomic nervous system, is further broken down into the sympathetic nervous system, enteric system and parasympathetic nervous system.


The sympathetic nervous system (SNS) starts at the vertebral column and the nerves of the system travel through the spine. Through the spine they target various organs of the body. Information is carried through the SNS, and the messages trigger various responses in the body. The messages travel very fast so that instant changes can be brought into the body, when you are facing a stressful situation. The flight or fight response caused travels through various parts of the body causing the necessary reactions.

The sympathetic nervous system carries out many functions like activating the body’s response under any stressful situation. It causes the flight or fight response in the body. The neural and hormonal stress response is mediated by the sympathetic nervous system. The stressful situations can be real or imaginary.

The functions of sympathetic nervous system have effects on several organs like:

  • It causes the dilation of the pupil in the eye by increasing it in one diameter.
  • It forces the tightening of the heart muscle by enhancing the heart rate. The sympathetic nervous system increases the blood pressure because of the contractions caused by the muscles.
  • It increases the dilation of the bronchioles so that airways are expanded and breathing becomes less laborious in stressful situations.
  • It stops the movement of food in the digestive system.
  • It affects the kidneys and causes it to release more rennin.
  • It also acts on the penis for faster ejaculation.

The sympathetic nervous system causes the response so that the human body is able to handle the stress. It is required to maintain homeostasis in the body. If the body comes under sudden stress, then the basal temperature drops rapidly. The sympathetic nervous system guards this basal temperature without letting it drop too low. We need the system so that blood supply to some organs is stopped when required. Stress whether physical or emotional can cause severe detrimental effects on all the parts of the body.

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