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A neuromuscular junction (or myoneural junction) is a chemical synapse between a motor neuron and a muscle fiber. [1] It allows the motor neuron to transmit a signal to the muscle fiber, causing muscle contraction. [2] Muscles require innervation to function—and even just to maintain muscle tone, avoiding atrophy.
In biology, a motor unit is made up of a motor neuron and all of the skeletal muscle fibers innervated by the neuron's axon terminals, including the neuromuscular junctions between the neuron and the fibres. [1] Groups of motor units often work together as a motor pool to coordinate the contractions of a single muscle.
Structure of neuromuscular junction. A neuromuscular junction is a chemical synapse formed by the contact between a motor neuron and a muscle fiber. [17] It is the site in which a motor neuron transmits a signal to a muscle fiber to initiate muscle contraction.
Involved in involuntary adjustment of head position in response to visual information. rubrospinal tract: from red nucleus to lower motor neurons: Involved in involuntary adjustment of arm position in response to balance information; support of the body. vestibulospinal tract: from vestibular nuclei, which processes stimuli from semicircular canals
A neuroeffector junction is a site where a motor neuron releases a neurotransmitter to affect a target—non-neuronal—cell. This junction functions like a synapse . However, unlike most neurons, somatic efferent motor neurons innervate skeletal muscle, and are always excitatory.
Several motorneurons compete for each neuromuscular junction, but only one survives until adulthood. [36] Competition in vitro has been shown to involve a limited neurotrophic substance that is released, or that neural activity infers advantage to strong post-synaptic connections by giving resistance to a toxin also released upon nerve stimulation.
Excitation of a myocyte causes depolarization at its synapses, the neuromuscular junctions, which triggers an action potential. With a singular neuromuscular junction, each muscle fiber receives input from just one somatic efferent neuron. Action potential in a somatic efferent neuron causes the release of the neurotransmitter acetylcholine. [27]
(b) A functional electrical stimulation system injects electrical current into the cell. (c) The intact but dormant axon receives the stimulus and propagates an action potential to (d) the neuromuscular junction. (e) The corresponding muscle fibers contract and generate (f) muscle force. (g) A train of negative pulses is produced.