The Autonomic and Somatic Nervous Systems

In the three previous articles [ NEUROLOGICAL BASIS OF BEHAVIOUR ] , [ THE CENTRAL NERVOUS SYSTEM AND BEHAVIOUR , [ THE PERIPHERAL NERVOUS SYSTEM (PNS) ] I showed simple information about them.

In this article I complete simple information about The Autonomic and Somatic Nervous Systems.

The PNS is further divided into the somatic nervous system and the autonomic nervous system. The somatic nervous system controls skeletal muscles to permit voluntary movement, such as walking or raising one’s hand, or chewing.  Autonomic means “self governing” and this nervous system is so described because it deals with unconscious and automatic behaviours, such as the regulation of organs (heart, blood vessels, stomach) and glands that help maintain bodily homeostasis.

The autonomic nervous system also contains two sub-systems:

1)- The sympathetic system – which stimulates action and output of energy to enable appropriate response;

2)- The parasympathetic system – which tends to inhibit action and conserve energy to ensure proper functioning.

In simple terms, these two subsystems act in different directions to prevent both inadequate and excessive or prolonged responses to stimuli. The sympathetic system activates most during stress or anxiety, where the parasympathetic system activates during relaxed states, and to return the body to homeostasis. The autonomic nervous system can only trigger one of two responses.  For example, it can start secretion in the digestive glands, or it can stop it. It can cause the sphincter in the bladder to contract or to relax.  It can make you sweat or have no effect on the sweat glands.  It can make your hair stand up on your arms or it can leave them lying normally.  This either/or triggering is called the sympathetic and parasympathetic response.