Function of ANS (Autonomic Nervous System)

The autonomic nervous system regulates vital functions like heart rate, digestion, respiration, and glandular activity.

Sympathetic Nervous System (Fight or Flight)
- Prepares the body for emergency or stressful situations.
- Physiological effects:
  - Heart: ↑ heart rate and force of contraction (β1)
  - Blood vessels: Vasoconstriction (α1) in skin and viscera; vasodilation (β2) in skeletal muscle
  - Lungs: Bronchodilation (β2)
  - Pupils: Dilation (mydriasis) via radial muscle contraction (α1)
  - GI tract: ↓ motility and secretions (α, β)
  - Urinary bladder: Relaxation of detrusor (β3), contraction of sphincter (α1)
  - Liver: ↑ glycogenolysis and gluconeogenesis (β2)
  - Adrenal medulla: Releases epinephrine and norepinephrine into circulation (via chromaffin cells activated by ACh on nicotinic receptors)
Parasympathetic Nervous System (Rest and Digest)
- Promotes maintenance activities and conserves energy.
- Physiological effects:
  - Heart: ↓ heart rate (M2)
  - Lungs: Bronchoconstriction and ↑ secretions (M3)
  - GI tract: ↑ motility and secretions (M3)
  - Urinary bladder: Contraction of detrusor, relaxation of sphincter (M3)
  - Pupils: Constriction (miosis) via circular muscle (M3)
  - Lacrimal/salivary glands: ↑ secretion (M3)