Acetylcholine: nicotinic, muscarinic and AChE
The first transmitter discovered — and a clear example of one messenger with a fast receptor and a slow one.
Where this fitsConnects to 1 · Unlocks 1
- Connects to
- Fast doors and slow keypads: ionotropic and metabotropic receptors — Nicotinic = ionotropic; muscarinic = metabotropic.
- Unlocks
- Other messengers: histamine, opioids, hormones and more — Anticholinergic side effects (e.g., diphenhydramine) come from blocking muscarinic receptors.
Walk through
Made from choline
Acetyl coenzyme A + choline (from diet or recycled) → acetylcholine.
Analogy and worked example
Analogy: One messenger, two phone lines: nicotinic is a direct line (instant), muscarinic goes through a switchboard (slower, more options). AChE is the operator who hangs up. Block the operator and the line stays jammed open.
Nerve gas irreversibly inhibits AChE. Predict the symptoms.
- AChE can't break down ACh → ACh builds up.
Tip: the ← and → keys move through the lesson.
Full lesson: Precursors and acetylcholine