Final answer:
Cholinergic receptors include nicotinic and muscarinic receptors. Both types of receptors bind to acetylcholine (ACh) and cause changes in the target cell. Nicotine and muscarine are specific molecules that bind to the nicotinic and muscarinic receptors, respectively.
Step-by-step explanation:
The cholinergic system includes two classes of receptors: the nicotinic receptor and the muscarinic receptor. Both receptor types bind to 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 named and differentiated by other molecules that bind to them. For example, nicotine binds to the nicotinic receptor, and muscarine binds to the muscarinic receptor. There is no cross-reactivity between the two receptors, similar to how different keys open different locks. However, acetylcholine (ACh) can bind to both types of receptors, acting as a master key that can open multiple locks.
These receptors play important roles in transmitting signals in the nervous system and are a focus of research in the laboratory. They are classified as exogenous, meaning they are made outside of the human body, allowing researchers to use them without any interference from endogenous molecules produced in the body.