Autonomic Nervous System

Human anatomy > Autonomic Nervous System

The autonomic nervous system, or ANS, is responsible for controlling several body responses which are under the conscious level and which are mostly involuntary, like breathing, digestion, sexual arousal, beating of the heart, and many other biochemical processes. There are two distinguishable divisions: the parasympathetic and the sympathetic nervous systems.

Autonomic nervous system

Parasympathetic Nervous System (PNS)

The hypothalamus is the center of the parasympathetic nervous system. It operates through various interconnecting systems and organs. This system is responsible in the “thinking” phase in stressful situations and is called the “Rest and Digest” phase because your body goes back to its normal responses.  

Sympathetic Nervous System (SNS)

This type of the autonomic nervous system is responsible in the distribution of essential nutrients and oxygen to the various parts of the body.  The ANS is responsible for “Flight or Fight.” The body has to respond immediately because of the urgency of some situations. You may either fight or run away. In these situations, your body responds accordingly and you are able to do impossible things, which you cannot do under normal circumstances. When your SNS responds, you can carry a very heavy object in times of a fire, but not when there isn't any.  You can do this because of the increase in energy brought about by the elevation of glucose in the bloodstream; thus, the pulse rate increases together with the respiration rate. Blood flow also is faster; hence, facilitating all the processes to allow the body to increase its performance.

Functions of the Autonomic System

  • Together with the hormones epinephrine and norepinephrine, it is responsible for the flight or fight response of the body. In cases like these, the heart rate increases, the respiration rate increases, oxygen absorption also increases, and you are able to gain more energy to take flight or to fight the stressful situation.
  • It helps maintain the body temperature through the activation of the sweat glands, which produces sweat when the body has an elevated temperature.
  • Through involuntary action of respiration involving inhalation and exhalation, the autonomic nervous system is able to detoxify the body by eliminating carbon dioxide through the lungs.  Carbon dioxide is considered a waste product, which is an acidic substance. If it is not excreted appropriately from the body, it can cause acidosis, which is detrimental to the body and can cause eventual death. The kidneys, gall bladder, liver, and skin are also involved in detoxifying the body.  Without the ANS, these functions would not be performed reliably.
  • It helps in the delivery of oxygen and other nutrients to where they are crucially needed.

Conditions Associated with the Autonomic Nervous System

Conditions associated with the ANS are those that affect the central nervous system. These conditions affect the brain, which is the center of the central nervous system.   Damage to the neurons or brain cells can cause instability to all bodily functions because the stimuli fed to the brain are not recognized properly.  Examples are brain tumors, brain cancers, damage to the hypothalamus and the vertebral column, and similar conditions that can damage any of the parts involved in the autonomic nervous system.


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