Parasympathetic Nervous system

The parasympathetic system or system vagal is one of three divisions of the autonomous or visceral Nervous system, with the Nervous system sympathetic nerve and the enteric Nervous system. The nervous fibers of the parasympathetic system take their origin in the parts cranial (nerves III, VII, IX and X) and crowned Spinal-cord. It controls the involuntary activities of the Organe S, Glande S, blood-vessels jointly with the one of the other parts of the autonomous nervous system: the Nervous system sympathetic nerve (sympathetic).

The parasympathetic system is responsible for the deceleration of the heart rate (cardio-regulator), of the increase in digestive secretions and the motility of the gastro-intestinal Tractus. It intervenes in certain pathological phenomena, such faindings or Lipothymie S (" faintness vagal"), phenomena colitic (Colitis), Diarrhea S, Vomiting S, Tear S, etc

Functions

Its effects are opposed to those of the nervous system sympathetic nerve (most of the time). Anatomically speaking, the parasympathetic ganglia are located in the crânio-crowned area of the spinal-cord (takes origin of the side horn of C1 with C8 and L4 with S5). The neuro-transmitter concerned with the effector junction is the Acétylcholine.

The general effects of a parasympathetic stimulation are the following: - bradycardia (Vagus responsible for faintness vagal). - increase in the intestinal peristalsis. - increase in gastric, salivary and intestinal secretions. - relaxation of the majority of the sphincters of the gastro-intestinal tract. - myosis (contraction of the iris).

See too

Sources

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