Psychology -> Sympathetic and parasympathetic divisions

Sympathetic and parasympathetic divisions

The main functions of the sympathetic and parasympathetic divisions of the ANS:

Bodily changes usually associated with, and physiological systems involved in arousal. The autonomic nervous system (ANS) has two divisions;

the sympathetic nervous system (arousing)
the parasympathetic nervous system (calming)
These two divisions are activated when you are aroused. During an emergency, the sympathetic division of the ANS takes over and prepares us for action; for fight or flight.

In contrast to the sympathetic division, the parasympathetic nervous system is responsible for calming the body down. When the emergency is over, the above physiological changes are reversed and your level of arousal is reduced. For example, if you are bushwalking and come across a dangerous situation, the sympathetic nervous system will be activated to enable you to fight the situation or flee from it. When the danger is over, the parasympathetic nervous system works on calming you down to achieve a state of homeostasis.

Sympathetic division
• Salivation inhibited
• Increased respiration
• Bronchial passages dilated
• Increased heart rate
• Digestion inhibited
• Secretion of adrenal
• hormones
• Increased secretions by sweat glands
• Hair follicles raised
• goose bumps
• Bladder relaxed
• Pupils dilated

Parasympathetic division
• Pupils constricted
• Salivation stimulated
• Decreased respiration
• Bronchial passages constricted
• Decreased heart rate
• Digestion stimulated
• Bladder contracted


These physiological changes equip the body with additional energy for self-protection.