Anatomical and Functional Differences of the Divisions of ANS

Parasympathetic: Functional

• “rest-and-digest”

• conserving energy, replenishing nutrients

• digestion, defecation, diuresis

• control of vsicerl organs during non-stressful situations

• low body energy

Sympathetic: Functional

• “fight-or-flight”

• exercise, excitement, emergency, embarrassment

• during stressful situations

• high body energy

• effects long duration and widespread

Parasympathetic: Anatomical

• preganglionic = long, postganglionic = short

  • ganglia close to/within effector organ

• preganglionic axon few branches

• CN III (pupil constriction), VII (lacrimal and salivary glands), IX (salivary glands), X (slowing heart rate, constricting lung bronchioles, increasing digestive secretions, storing CHO)

• S2-S4 include smooth muscle contraction, increased urinary and digestive system secretions, penile and clitoral erection

Sympathetic: Anatomical

• preganglionic = short, postganglionic = long

  • ganglia close to sc (lateral or anterior)

• preganglionic many branches

Degree of Response

parasympathetic

• localized and short duration

  • long preganglionic with limited branches influence one/few effectors at same time

sympathetic

• mass activation

  • short preganglionic with many branches simultaneously influence several effectors

• sometimes single effector engaged = pupil dilation in low light