Autonomic nervous system | Cholinergic Receptors

Introduction to autonomic nervous system

The nervous system is divided into two anatomical divisions; the central nervous system( CNS) which is composed of the brain and spinal cord and the supplemental nervous system which include neurons located outside the brain and spinal cord for illustration jitters that enter or leave the central nervous system.

 The supplemental nervous system comprises of physical nervous system and autonomic nervous system.

The somatic nervous system is involved in the voluntary control of functions and the autonomic nervous system is involved in the involuntary control of functions such as blood flow, respiration, digestion, cardiac output and glandular secretions.

The enteric nervous system is a semiautonomous character of the ANS present in the GIT, with unique functions for the standard of this organ system. This system correspond of the myenteric supersystem and the meissner supersystem that transferred sensitive input to the parasympathetic and sympathetic nervous system and admit motor affair from them.

The endocrine system send signal to target tissues by varying level of blood-borne hormones.

In discrepancy, the nervous system exerts its influence by the rapid-fire transmission of electrical impulses over whim-whams fibres that terminate at effector cells which specifically respond to the release of neuromediator substances.

Medicines that produce their primary remedial effect by mimicking or altering the functions of autonomic nervous system are called autonomic medicines.

These autonomic agents take action by stimulating portions of the autonomic nervous system or by blocking the activity of the autonomic nervous.

The sympathetic system has a huge distribution, innervating affecters all over the body whereas parasympathetic system is fairly limited.

Parasympathetic nervous system:

This system controls visceral functions under normal conditions.

It consists of cranial nerves 3rd, 7th, 9th, 10th and fibres arising from sacral segments (usually S2-S4) of spinal cord.

Parasympathomimetics (cholinergic agonists):

These agents act on receptors that are actuated by acetylcholine.

The receptors on which these agents act are nominated as cholinergic receptors or cholinoceptors.

Cholinergic Receptors( cholinoceptors)

Cholinergic Receptors

There are two kind of cholinergic receptors which are different from each other on the base of their different affections for agents that mimic the activity of acetylcholine( cholinomimetic agents), these receptors are given below;

  1. Muscarinic receptors
  2. Nicotinic receptors

Muscarinic receptors:

  • These receptors also recognize Muscarine (an alkaloid present in certain poisonous mushrooms) in addition to binding acetacholine.
  • They show only a less affinity for Nicotine.
  • There are five sorts of muscarinic receptors; M- 1, M- 2, M- 3, M- 4 and M- 5.
  • All five are G protein coupled receptors.
  • M-1, M-3 and M-5 lead to cellular excitation whereas M-2 and M-4 inhibit cellular excitability.

Location of Muscarinic receptors:

Muscarinic receptors are located on;

The ganglia of the peripheral nervous system.

The autonomic effector organs such as heart, brain, smooth muscles and exocrine glands.

Location of M-1 receptors:

M-1 receptors are located on central nervous system neurons, sympathetic postganglionic cell bodies and many presynaptic sites.

Location of M-2 receptors:

M-2 receptors are present in the myocardium, smooth muscle organs and some neuronal sites.

Location of M-3 receptors:

M-3 receptors are located on bladder, exocrine glands, endothelium and smooth muscle cells.

Location of M-4 and M-5 receptors:

M-4 and M-5 receptors are less important and appear to play a greater role in the central nervous system than in the periphery.

Nicotinic receptors

These receptors also recognize nicotine in addition to binding acetylcholine.

They show only a weak affinity Muscarine.

Location of Nicotinic receptors:

These are located in the;

  • Central nervous system
  • Adrenal medulla
  • Autonomic ganglia (both sympathetic and parasympathetic)
  • Neuromuscular junction

Learn more

Autonomic nervous system

Introduction to autonomic nervous system

What is autonomic nervous system?

What is parasympathetic nervous system?

What are parasympathomimetics?

What are cholinergic agonists?

What is cholinergic receptors?

What is cholinoceptors?

There are how many types of cholinergic receptors?

What are the two types of cholinergic receptors?

What is Muscarinic receptors?

What is nicotinic receptors?

There are how many subclasses of muscarinic receptors?

What is M-1 receptors?

What is M-2 receptors?

What is M-3 receptors?

What is M-4 receptors?

What is M-5 receptors?

What is the location of muscarinic receptors?

What is the location of M1 receptors?

What is the location of M2 receptors?

What is the location of M3 receptors?

What is the location of M4 receptors?

What is the location of M5 receptors?

What is the location of nicotinic receptors?

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