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Also called nicotinic acetylcholine receptors, nicotinic receptors are cells that respond to nicotine, a neurotransmitter. These cells function mainly in the autonomic nervous system of the body. Nicotinic receptors are a type of acetylcholine receptor, which can also be called a cholinergic receptor. A receptor is a part of a cell that attaches to certain chemicals in a process called binding, which triggers the cell to react within the body. In addition to nicotine, the action of nicotinic receptors is triggered by acetylcholine (ACh), another common neurotransmitter.
When nicotine triggers nicotinic receptors, its molecules are considered to be ligands, or types of molecules that trigger receptors. Varieties of receptor-triggering ligands include inhibitors, neurotransmitters, activators, and substrates. Aside from the ACh that triggers nicotinic receptors, other types of neurotransmitters include serotonin, dopamine, and norepinephrine.
Nicotinic receptors also fall under the category of an ionotropic receptor. An ionotropic receptor is a type of receptor that converts the ligand into an electrical signal. With their quick-fire means of function, ionotropic receptors are in contrast with metabotropic receptors. Metabotropic receptors send their biological messages through the cell using a somewhat slower diffusion of chemicals throughout the body of the cell in which the receptor is located. One example of a metabotropic receptor is the muscarinic acetylcholine receptor, a receptor charged with regulating the distribution of acetylcholine in the body, as well as other tasks within the body and brain.
Cholinergic receptors are a type of autonomic receptor that are activated by ACh, which mainly work on organs and vital processes like the digestive and cardiovascular systems. Parts of the autonomic system include the sympathetic nervous system, the parasympathetic nervous system, and the enteric nervous system. Generally, the sympathetic nervous system is responsible for responses to threats, often called fight-or-flight responses. The parasympathetic nervous system is responsible for bodily functions performed at rest, like digestion and bodily waste removal processes, particularly those in the bladder. A little-understood part of the body, the enteric nervous system is a complicated system of nerves responsible for advanced functions related to digestion and digestive organs.
The muscarinic receptor and the nicotinic receptor are the two major types of cholinergic receptor, another name for an acetylcholine receptor. Though muscarinic receptors primarily respond to muscarine, they do also respond to nicotine to a lesser degree. Muscarine has been isolated as a chemical in some types of mushrooms, though they are usually unsafe to eat.