Parasympathetic nervous system

The parasympathetic nervous system is part of the autonomic nervous system and has the following functions:

• Dilates blood vessels leading to the GI tract, increasing blood flow. This is important following the consumption of food, due to the greater metabolic demands placed on the body by the gut.

• The parasympathetic nervous system can also constrict the bronchiolar diameter when the need for oxygen has diminished.

• During accommodation, the parasympathetic nervous system causes constriction of the pupil and lens.

• The parasympathetic nervous system stimulates salivary gland secretion, and accelerates peristalsis, so, in keeping with the rest and digest functions, appropriate PNS activity mediates digestion of food and indirectly, the absorption of nutrients.

• Is also involved in erection of genitals, via the pelvic splanchnic nerves 2–4.