Neuromuscular junction Health Dictionary

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  2. Neuromuscular Junction

Neuromuscular Junction: From 2 Different Sources

The area where a motor NERVE ends close to the MUSCLE membrane so can initiate muscle contraction. The motor-nerve ending is separated from the motor end plate by the synaptic cleft which is only 50–70 nm wide. When a nerve impulse arrives at the motor-nerve ending, molecules of ACETYLCHOLINE are released which cross the synaptic cleft and attach to receptors on the motor end plate. This initiates depolarisation of the muscle which in turn initiates the process of contraction. Acetylcholinesterase (an ENZYME) rapidly breaks down the molecules of acetylcholine, thus ending their action and freeing the receptor in preparation for the next impulse.
Health Source: Medical Dictionary
Author: Health Dictionary
(myoneural junction) the meeting point of a nerve fibre and the muscle fibre that it supplies. Between the enlarged end of the nerve fibre (motor end-plate) and the membrane of the muscle is a gap across which a *neurotransmitter must diffuse from the nerve to trigger contraction of the muscle.
Health Source: Oxford | Concise Colour Medical Dictionary
Author: Jonathan Law, Elizabeth Martin

Neuromuscular Blockade

In clinical practice, the transmission of impulses at the NEUROMUSCULAR JUNCTION may be blocked to paralyse temporarily a patient for a surgical procedure, or to assist treatment on the intensive care unit. There are two main types of drug, both of which competitively block the ACETYLCHOLINE receptors on the motor end plates. (1) Depolarising neuromuscular blocking agents: these act by ?rst producing stimulation at the receptor, and then by blocking it. There are characteristic muscle fasciculations before the rapid onset of paralysis which is of short duration (less than ?ve minutes with the commonly used drug, suxamethonium). The drug is removed from the receptor by the enzyme, CHOLINESTERASE.

(2) Non-depolarising neuromuscular blocking agents: these drugs occupy the receptor and prevent acetylcholine from becoming attached to it. However, in su?ciently high concentrations, acetylcholine will compete with the drug and dislodge it from the receptor; the e?ect of these drugs is reversed by giving an anticholinesterase, which allows the amount of acetylcholine at the neuromuscular junction to build up. These drugs have varying durations of action, but all are slower in onset and of longer duration than the depolarisers.... neuromuscular blockade

Junction

n. (in anatomy) the point at which two different tissues or structures are in contact. See also neuromuscular junction.... junction

Junctional Epithelium

(JE) (in dentistry) the stratified squamous *epithelium that is directly attached to the surface of a tooth; it has a protective function against periodontal diseases.... junctional epithelium

Myoneural Junction

see neuromuscular junction.... myoneural junction

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