Definition for Cholinergic receptor
From Biology Forums Dictionary
Cholinergic refers to responses in various systems to the natural transmitter molecule Acetlycholine (ACh). Cholinergic receptors are subclassified into two categories, Nicotinic and Muscarinic, named for the extrinsic compounds that stimulate only that category. The properties of the two categories are summarized as follows:
Nicotinic Receptors
- Stimulated by ACh and nicotine, not stimulated by muscarine.
- Found at all ganglionic synapses.
- Also found at neuromuscular junctions.
- Blocked by hexamethonium.
The physiological responses to stimulation and block are complex since both the sympathetic and parasympathetic systems are affected. The final response of any one organ system depends on which system has a stronger tonic influence.
For example, under normal circumstances, the heart receives more parasympathetic influence than sympathetic. Ganglionic blockade would lower the parasympathetic influence more than the sympathetic, and thus the heart rate would increase.
Muscarinic Receptors
- Stimulated by ACh and muscarine, not stimulated by nicotine.
- Found at target organs when ACh is released by post-ganglionic neurons (all of parasympathetic, and some sympathetic).
- Stimulated selectively by Muscarine, Bethanechol.
- Blocked by Atropine.