Search results
Results From The WOW.Com Content Network
Acetylcholine is a choline molecule that has been acetylated at the oxygen atom. Because of the charged ammonium group, acetylcholine does not penetrate lipid membranes. . Because of this, when the molecule is introduced externally, it remains in the extracellular space and at present it is considered that the molecule does not pass through the blood–brain
The parasympathetic nervous system, which uses acetylcholine almost exclusively to send its messages, is said to be almost entirely cholinergic. Neuromuscular junctions, preganglionic neurons of the sympathetic nervous system , the basal forebrain , and brain stem complexes are also cholinergic, as are the receptor for the merocrine sweat glands.
[1] [3] [4] According to their site of actions, cholinergic blocking drugs can be classified into two general types — antimuscarinic and antinicotinic agents. [1] Antimuscarinic agents (also known as muscarinic antagonists), including atropine and hyoscine, block acetylcholine at the muscarinic acetylcholine receptors.
The neurotransmitters of postganglionic fibers differ: In the parasympathetic division, neurons are cholinergic.That is to say acetylcholine is the primary neurotransmitter responsible for the communication between neurons on the parasympathetic pathway.
Similarly, acetylcholine released from parasympathetic neurons may interact with M 2 and M 4 receptors to inhibit further release of acetylcholine. An atypical example is given by the β-adrenergic autoreceptor in the sympathetic peripheral nervous system, which acts to increase transmitter release. [1]
[1] This phenomenon is known as an excitatory postsynaptic potential (EPSP). It may occur via direct contact between cells (i.e., via gap junctions ), as in an electrical synapse , but most commonly occurs via the vesicular release of neurotransmitters from the presynaptic axon terminal into the synaptic cleft , as in a chemical synapse .
[72] [note 1] Nicotine, a compound found in tobacco, is a direct agonist of most nicotinic acetylcholine receptors, mainly located in cholinergic neurons. [67] Opiates , such as morphine , heroin , hydrocodone , oxycodone , codeine , and methadone , are μ-opioid receptor agonists; this action mediates their euphoriant and pain relieving ...
[1] [4] Chemicals in this family can act either directly by stimulating the nicotinic or muscarinic receptors (thus mimicking acetylcholine), or indirectly by inhibiting cholinesterase, promoting acetylcholine release, or other mechanisms. [5] Common uses of parasympathomimetics include glaucoma, Sjögren syndrome and underactive bladder. [6]