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Sunday, 24 July 2016


The autonomic nervous system is the part of the nervous system concerned with the control of the involuntary actions of the. body.

The autonomic nervous system is divided into two parts, namely: the sympathetic nervous system (thoracolumbar outflow) and the _ parasympathetic (craniosacral outflow) nervous system.

The effects of autonomic control are essential for homeostasis and include stimulation or depression of glandular secretions and contraction of cardiac and smooth muscle tissues.

SYMPATHETIC NERVOUS SYSTEM Most preganglionic fibres of the sympathetic division arise from the middle or thoracic-lumbar portion of the spinal cord and almost immediately terminate in the ganglia that lie near the cord. 'Therefore, in this division, the preganglionic fibre is short, but the postganglionic fibre that makes contact with an organ is long. The sympathetic division is especially important during emergency situations when an individual is required to fight or take flight.

It accelerates the heartbeat and dilate: the bronchi; which makes glucose and Oxygen readily available to active muscles. On the on“,
hand, the sympathetic division inhibits the digestive tractdigestion; which is not an immediate necessity when one is under attack.

Parasympathetic division includes: a few cranial nerves, e.g. the vagus nerve, as well as fibres that arise from the sacral portion of the spinal cord. Therefore, this division is often referred to as the craniosacral portion of the autonomic system. In the parasympathetic division the preganglionic iibre is long while the postganglionic fibre is short because the ganglia lie near or within the organ.

The parasympathetic division, sometimes also called the housekeeper division, promotes all the internal responses that are associated with a relax state, for example, it causes the pupil of the eye to constrict, promotes digestion of food by causing the flow of saliva and other gut secretions, and retards the heartbeat. The parasympathetic division brings about the responses associated with a relaxed state while sympathetic division is associated with those
responses associated with ‘tight’ or fight’.

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