Acetylcholine has many roles.

When it binds to muscarinic receptors, it:

    Regulates heart contractions and blood pressure and decreases heart rate.
    Moves food through your intestine by contracting intestinal muscles and increasing stomach and intestine secretions.
    Causes glands to secrete substances such as tears, saliva, milk, sweat and digestive juices.
    Controls the release of urine.
    Contracts muscles that control near vision.
    Causes an erection.

When it binds to nicotinic receptors, it:

    Allows skeletal muscle to contract.
    Causes the release of adrenaline and norepinephrine from your adrenal glands.
    Activates your sympathetic system with the release of norepinephrine.

Both types of receptors are involved in memory, including long-term and working memory, memory formation and consolidation and retrieval.

Within your brain, acetylcholine is also involved in motivation, arousal, attention, learning and promoting rapid eye movement (REM) sleep.