Some science behind the scenes

Parasympathetic nervous system

The Parasympathetic nervous system maintains normal functioning of the body in non threatening situations.  It helps keep the body in a relaxed unstressed condition.  If we stimulate the parasympathetic nerves it can:

  • Reduce the heart rate – because we don’t need the oxygen, we are ‘at rest’
  • Cause us to have an erection – the smooth muscles relax [limp willies are caused by contraction not relaxation]
  • Stimulate the pancreas, stomach and intestines to work – again the smooth muscle are relaxed and get to work
  • Constrict our pupils
  • Constrict the bronchioles  - because more oxygen is not needed, the lung capacity does not need to be so large
  • Stimulate urination – we don’t need all the water we have retained in order to sweat and breathe heavily for the  ‘flight’ response, so we get rid of it by weeing
  • Dilates the blood vessels to the gut to help in digestion of any food we might eat to build up our reserves of energy
  • Stimulate saliva production

These nerves have ‘cholinergic’ nerve endings and use acetycholine as the neurotransmitter.


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