The nervous system enables humans to react to their surroundings and to coordinate their behaviour. It comprises millions of neurones and uses electrical impulses to communicate very quickly.
The ANS consists of two antagonistic systems:
| Sympathetic (fight or flight) | Parasympathetic (rest and digest) | |
|---|---|---|
| Heart Rate | Increase in rate of contraction of cardiac muscle - cardiac output increases | Decrease in rate of contraction of cardiac muscle - cardiac output decreases |
| Breathing Rate | Smooth muscle of bronchioles relaxes - intake of air increases | Smooth muscle of bronchioles contracts - intake of air decreases |
| Peristalsis | Smooth muscle of digestive tract contracts less - rate of peristalsis decreases | Smooth muscle of digestive tract contracts more - rate of peristalsis increases |
| Intestinal Secretions | Action of glands is inhibited - decrease in production of secretions | Action of glands is stimulated - increase in production of secretions |