Which neurotransmitter activates muscarinic receptors in the parasympathetic system?

The neurotransmitter that activates muscarinic receptors in the parasympathetic system is acetylcholine. In the autonomic nervous system, the parasympathetic division primarily uses acetylcholine as its neurotransmitter. When released from postganglionic neurons, acetylcholine binds to muscarinic receptors on target tissues, leading to various physiological responses associated with the rest-and-digest state.

Muscarinic receptors are a type of cholinergic receptor that play a key role in mediating the effects of acetylcholine in the body, which include decreasing heart rate, increasing glandular secretions, and promoting digestion. This receptor activation helps facilitate the body’s normal functions during restful states, allowing energy conservation and regenerative processes to occur.

In contrast, other neurotransmitters such as dopamine, norepinephrine, and serotonin serve different roles in the nervous system, with examples including norepinephrine primarily acting in the sympathetic nervous system and influencing a fight-or-flight response rather than the parasympathetic processes activated by acetylcholine.