anticholinergic(redirected from Cholinergic antagonists)
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1. blocking the passage of impulses through the parasympathetic nerves.
2. an agent that has this effect; called also parasympatholytic.
Antagonistic to the action of parasympathetic or other cholinergic nerve fibers (for example, atropine).
Inhibiting or blocking the physiological action of acetylcholine at a receptor site: anticholinergic drugs.
anticholinergicadjective Referring to an agent or effect that suppresses or inhibits acetylcholine activity.
noun Any agent that inhibits parasympathetic activity by blocking the neurotransmitter acetylcholine; anticholinergics are used for asthma, COPD, diarrhoea, nausea, vomiting, Parkinson’s disease and to decrease smooth muscle spasms (e.g., in the urinary bladder); anticholinergics may be antimuscarinic, ganglionic blockers and neuromuscular blockers.
anticholinergicParasympatholytic adjective Referring to an agent or effect that suppresses or inhibits acetylcholine activity noun Any agent that inhibits parasympathetic activity by blocking the neurotransmitter, acetylcholine; anticholinergics are used for asthma, COPD, diarrhea, N&V, Parkinson's disease, and to ↓ smooth muscle spasms–eg, in the urinary bladder; anticholinergics may be antimuscarinic, ganglionic blockers, and neuromuscular blockers
1. Antagonistic to the action of parasympathetic or other cholinergic nerve fibers (e.g., atropine).
2. Any of a class of compounds exerting anticholinergic effects. Some of these compounds (e.g., atropine) are used medicinally.
anticholinergicAntagonistic to the action of acetyl choline or to the parasympathetic or other CHOLINERGIC nerve supply. Acetyl choline stimulates muscle contraction in the intestines and elsewhere and slows the heart. Anticholinergic substances, such as ATROPINE, relieve muscle spasm, dilate the pupils and speed up the heart.
Blocking the action of the neurohormone acetylcholine. The most obvious effects include dry mouth and dry eyes.
A neurotransmitter substance with special excitatory properties of all preganglionic autonomic neurons, all parasympathetic postganglionic neurons and a few postganglionic sympathetic neurons. Acetylcholine is synthesized and liberated by the action of the enzyme choline acetyltranferase from the compounds choline and acetyl coenzyme A (acetyl CoA) which occurs in all cholinergic neurons. ACh exists only momentarily after its formation, being hydrolysed by the enzyme acetylcholinesterase which is present in the neurons of cholinergic nerves throughout their entire lengths and at neuromuscular junctions: this process is essential for proper muscle function as otherwise the accumulation of ACh would result in continuous stimulation of the muscles, glands and central nervous system. Alternatively a shortage of ACh has devastating effect (e.g. myasthenia gravis). ACh binds to acetylcholine receptors on skeletal muscle fibres. Sodium enters the muscle fibre membrane, which leads to a depolarization of the membrane and muscle contraction. There are two main types of acetylcholine receptors (cholinergic receptors): muscarinic receptors, which are stimulated by muscarine and ACh, belong to a family of G proteins coupled receptors and are situated in parasympathetically innervated structures (e.g. the iris and ciliary body); and nicotine receptors, which are stimulated by nicotine and ACh, are ligand-gated receptors and are situated in striated muscles (e.g. the extraocular muscles). Cholinergic receptors are found in the sympathetic and parasympathetic nervous systems, in the brain and spinal cord. The action of ACh can be either blocked or stimulated by drugs: Anticholinesterase drugs (e.g. neostigmine) inhibit acetylcholinesterase and prolong the action of acetylcholine whereas antimuscarinic drugs (also referred to as anticholinergics or parasympatholytics) such as atropine, cyclopentolate, homatropine, hyoscine and tropicamide inhibit the action of acetylcholine at muscarinic receptors. Other drugs mimic the action of ACh, they are known as parasympathomimetics (e.g. pilocarpine). See cholinergic; cycloplegia; miotics; mydriatic; neurotransmitter; nicotine; synapse; autonomic nervous system.
Antagonistic to the action of parasympathetic or other cholinergic nerve fibers (e.g., atropine).