acetylcholine /ac·e·tyl·cho·line/ (ACh) (as″ĕ-til-) (as″ĕ-tēl-ko´lēn) the acetic acid ester of choline, which is a neurotransmitter at cholinergic synapses in the central, sympathetic, and parasympathetic nervous systems; used in the form of the chloride salt as a miotic.
Acetylcholine
acetylcholine (ACh)
acetylcholine (ACh) [as″ĕ-til-ko´lēn]
acetylcholine (
·sēˈ·tl·kōˑ·lēn),
acetylcholine (as´
tilkō´lēn, sē´til),
acetylcholine
a·ce·tyl·cho·line ( -s t l-k  ln)n. Abbr. Ach A white crystalline derivative of choline that is released at the ends of nerve fibers in the somatic and parasympathetic nervous systems and is involved in the transmission of nerve impulses in the body. |
Acetylcholine
a molecule released by neurons at the neuromuscular junction that causes muscle contraction.
acetylcholine (ACh)
[as′ətilkō′lēn, əsē′til-]
a direct-acting cholinergic neurotransmitter agent widely distributed in body tissues, with a primary function of mediating the synaptic activity of the nervous system and skeletal muscles. Its half-life and duration of activity are short because it is rapidly destroyed by acetylcholinesterase. Its activity also can be blocked by atropine at the junctions of nerve fibers with glands and smooth muscle tissue. It is a stimulant of the vagus and autonomic nervous system and functions as a vasodilator and cardiac depressant. Acetylcholine is used therapeutically as an adjunct to eye surgery and has limited benefits in certain circulatory disorders because of its short half-life.
acetylcholine (ACh) [as″ĕ-til-ko´lēn]
the acetic acid ester of choline, normally present in many parts of the body and having important physiologic functions. It is a neurotransmitter at cholinergic synapses in the central, sympathetic, and parasympathetic nervous systems. Used in medicine as a miotic.
acetylcholine (
·sēˈ·tl·kōˑ·lēn),n neurotransmitter that is produced in the central and parasympathetic autonomic nervous systems. It is the most prevalent neurotransmitter in the body and is crucial to arousal, learning, memory, and motor function.
acetylcholine (as´
tilkō´lēn, sē´til),n 1. an acetate ester of choline that serves as a neurohumoral agent in the transmission of an impulse in autonomic ganglia, parasympathetic postganglionic fibers, and somatic motor fibers.
n 2. an ester of choline actively involved as a chemical mediator at the neuromuscular junction, at autonomic ganglia, and between parasympathetic nerve endings and visceral effectors.
n 2. an ester of choline actively involved as a chemical mediator at the neuromuscular junction, at autonomic ganglia, and between parasympathetic nerve endings and visceral effectors.
acetylcholine
the acetic acid ester of choline, normally present in many parts of the body and having important physiological functions. It is a neurotransmitter at cholinergic synapses in the central, sympathetic and parasympathetic nervous systems. It is not used clinically but it is the classical cholinergic agonist. Abbreviated ACh.
acetylcholine receptors
structures located at the endorgans, e.g. at the skeletal muscle fibers. The myofibers are stimulated to contract by the interaction of acetylcholine with acetylcholine receptors which are located on the motor end plate or postsynaptic sarcolemma. See also neuromuscular junction.
acetylcholine (ACh)
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.
acetylcholine
Neurophysiology An acetic acid ester of choline-a substance that functions as a major cholinergic neurotransmitter released from vertebrate neurons into the synaptic spaces after stimulation from the PNS Action Vasodilation,
cardiac inhibition, GI peristalsis; it is involved in the control of thought, mood, sleep, muscles, bladder, sweat glands
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