Final answer:
The cholinergic system includes two classes of receptors: the nicotinic receptor and the muscarinic receptor. These receptors are differentiated by other molecules that bind to them, such as nicotine and muscarine. There are several types of muscarinic receptors, known as M1-M5 receptors.
Step-by-step explanation:
The cholinergic system includes two classes of receptors: the nicotinic receptor and the muscarinic receptor. Both receptor types bind to acetylcholine (ACh) and cause changes in the target cell. The nicotinic receptor is a ligand-gated cation channel, while the muscarinic receptor is a G protein-coupled receptor. The receptors are differentiated by other molecules that bind to them, such as nicotine for the nicotinic receptor and muscarine for the muscarinic receptor.
There are several types of muscarinic receptors, known as M1-M5 receptors. However, the drugs that target these receptors are not usually specific to the individual receptor types. Parasympathetic drugs can either be muscarinic agonists or antagonists, or indirectly affect the cholinergic system. Drugs that enhance cholinergic effects are referred to as parasympathomimetic drugs, while those that inhibit cholinergic effects are called anticholinergic drugs.