Sympathetic and Parasympathetic Nervous System SLO: 1.3.3 – Differentiating between the functions of the sympathetic and parasympathetic system

Both Systems: Most organs are supplied by both sympathetic and parasympathetic fibers, and the two systems generally have opposite effects.

The Sympathetic System Tends to act as an accelerator for those organs needed to meet a stressful situation. It promotes the fight or flight response Stimulated by the 4 “Es” Emergency Excitement Embarrassment Exercise

Effects of the Sympathetic System: Increase in the rate and force of heart contractions Increase in blood pressure due partly to the more effective heartbeat and partly to constriction of small arteries everywhere except the brain Dilation of blood vessels to skeletal muscles, bringing more blood to these tissues Dilation of the bronchial tubes to allow more oxygen to enter and more carbon dioxide to leave Stimulation of the central portion of the adrenal gland

Effects of the Sympathetic System: Increase in basal metabolic rate Dilation of the eye’s pupil and increase in distance focusing ability

Sympathetic System – Only what’s necessary! The sympathetic system also acts as a brake on those systems not directly involved in the stress response, such as the urinary and digestive systems (example: difficulty eating when angry)

Parasympathetic System The parasympathetic system normally acts as a balance for the sympathetic system once a crisis has passed The “Rest and Digest” system Causes: Constriction of pupils Slowing of heart rate Constriction of bronchial tubes Stimulates activities to maintain homeostasis Promotes the formation and release of urine and the activity of the digestive system