Autonomic Nervous System
The branch of the nervous system that runs the body’s automatic, involuntary functions — heartbeat, digestion, breathing rate, blood pressure, and gland activity. Abbreviated ANS.
Two opposing divisions
Section titled “Two opposing divisions”- Sympathetic — the “fight-or-flight” response: speeds the heart, widens the airways, redirects blood to muscle.
- Parasympathetic — the “rest-and-digest” state: slows the heart, promotes digestion, conserves energy.
- Enteric — a third division that governs the gut semi-independently.
What it does
Section titled “What it does”Keeps internal conditions stable without conscious effort, constantly balancing its divisions against one another.
Key idea
Section titled “Key idea”Most organs receive both sympathetic and parasympathetic input; their state at any moment reflects the tug-of-war between the two. See also the endocrine system, the body’s slower control network.