Difference Between Adrenergic and Cholinergic Receptors

The key difference between adrenergic and cholinergic receptors is that the adrenergic receptors are G protein-coupled receptors that bind to the neurotransmitters noradrenaline (norepinephrine) and adrenaline (epinephrine) while the cholinergic receptors are inotropic and metabotropic receptors that bind to acetylcholine neurotransmitters.  

The autonomic nervous system is one of the major components of the nervous system in our body. It is responsible for controlling the actions which are not doing with a conscious recognition or effort by the organism. Examples of such kinds of acts are breathing, heart rate, blood pressure, urination, digestion, defecation, body temperature, etc. Therefore, the two major divisions of the autonomic nervous system are sympathetic nervous system and parasympathetic nervous system. These two systems use chemical messengers or the neurotransmitters to communicate within the nervous system. Acetylcholine and norepinephrine are two main types of chemical messengers that secreted by these nerve fibers.

CONTENTS

1. Overview and Key Difference
2. What are Adrenergic Receptors
3. What are Cholinergic Receptors
4. Similarities Between Adrenergic and Cholinergic Receptors
5. Side by Side Comparison – Adrenergic vs Cholinergic Receptors in Tabular Form
6. Summary

What are Adrenergic Receptors?

Adrenergic receptors are the receptors that bind and respond to noradrenaline (norepinephrine) and adrenaline (epinephrine). These receptors are G protein-coupled receptors mainly involved with the sympathetic nervous system.

Furthermore, there are two adrenergic receptors namely α-receptors Alpha 1 and 2) & β-receptors (beta 1, 2 and 3). Beta 2 receptors have a higher affinity towards adrenaline while alpha receptors show a higher affinity towards noradrenaline. Among these receptors, α1 & β1 are responsible for excitation while α2 & β2 are responsible for inhibition.

What are Cholinergic Receptors?

Cholinergic receptors are the second type of receptors used in the autonomic nervous system. Cholinergic neurons release acetylcholine. These receptors are inotropic and metabotropic. And, they bind and respond to acetylcholine and facilitate communication.

Moreover, cholinergic receptors involve the parasympathetic nervous system. There are two types of cholinergic receptors namely muscarinic and nicotinic receptors. Muscarinic receptors locate on all visceral organs.

What are the Similarities Between Adrenergic and Cholinergic Receptors?

• Adrenergic and Cholinergic Receptors are two autonomic receptors.
• They respond to neurotransmitters.
• Both trigger nerve impulses.

What is the Difference Between Adrenergic and Cholinergic Receptors?

Adrenergic receptors work in the sympathetic nervous system. They bind to adrenaline and noradrenaline. On the other hand, cholinergic receptors work in the parasympathetic nervous system. They bind to acetylcholine. There are two main types of adrenergic receptors (alpha and beta) while there are two cholinergic receptors namely nicotinic and muscarinic. The below infographic presents the difference between adrenergic and cholinergic receptors in tabuar form.

Summary – Adrenergic vs Cholinergic Receptors

Adrenergic and cholinergic are two receptors in the autonomic nervous system. Adrenergic receptors work for the sympathetic nervous system while cholinergic receptors work for the parasympathetic nervous system. Moreover, adrenergic and cholinergic receptors respond to adrenaline/noradrenaline and acetylcholine respectively. This is the difference between adrenergic and cholinergic receptors.

Reference:

1.“CVANS: The Structure Function.” Structure and Function of Skeletal Muscle. Available here  
2.“Adrenergic Receptor.” Wikipedia, Wikimedia Foundation, 31 July 2018. Available here 

Image Courtesy:

1.”Adrenoceptor-Signal transduktion”By Sven Jähnichen. Partially translated by Mikael Häggström (CC BY-SA 3.0) via Commons Wikimedia  
2.”Muscarinic acetylcholine receptor M2-3UON”By Takuma-sa – Own work, (CC0) via Commons Wikimedia