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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 .
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.
In the histology of skeletal muscle, a triad is the structure formed by a T tubule with a sarcoplasmic reticulum (SR) known as the terminal cisterna on either side. [1] Each skeletal muscle fiber has many thousands of triads, visible in muscle fibers that have been sectioned longitudinally. (This property holds because T tubules run ...
In skeletal muscle, at the end of each muscle fiber, the outer layer of the sarcolemma combines with tendon fibers at the myotendinous junction. [ 16 ] [ 17 ] Within the muscle fiber pressed against the sarcolemma are multiply flattened nuclei ; embryologically, this multinucleate condition results from multiple myoblasts fusing to produce each ...
In the muscle-type receptors, found at the neuromuscular junction, receptors are either the embryonic form, composed of α 1, β 1, γ, and δ subunits in a 2:1:1:1 ratio ((α 1) 2 β 1 γδ), or the adult form composed of α 1, β 1, δ, and ε subunits in a 2:1:1:1 ratio ((α 1) 2 β 1 δε).
Visceral efferent neurons innervate smooth muscle, cardiac muscle, and glands, and have the ability to be either excitatory or inhibitory in function. Neuroeffector junctions are known as neuromuscular junctions when the target cell is a muscle fiber. Non-synaptic transmission is characteristic of autonomic neuroeffector junctions.
Each alpha motor neuron and the extrafusal muscle fibers innervated by it make up a motor unit. [1] The connection between the alpha motor neuron and the extrafusal muscle fiber is a neuromuscular junction, where the neuron's signal, the action potential, is transduced to the muscle fiber by the neurotransmitter acetylcholine.
These impulses move to the neuromuscular junction (NMJ) of skeletal muscle via peripheral axons after synapsing with the lower motor neurons through the ventral horn of the spinal cord. A signal that travels to the NMJ, which innervates muscles, is produced by the release of acetylcholine by upper motor neurons.