neurotransmitter secretion involved in regulation of skeletal muscle contraction

Definition

Target type: biologicalprocess

The regulated release of neurotransmitter into the synaptic cleft involved in skeletal muscle contraction. A neurotransmitter is any of a group of substances that are released on excitation from the axon terminal of a presynaptic neuron of the central or peripheral nervous system and travel across the synaptic cleft to either excite or inhibit the target cell. Among the many substances that have the properties of a neurotransmitter are acetylcholine, noradrenaline, adrenaline, dopamine, glycine, gamma aminobutyrate, glutamic acid, substance P, enkephalins, endorphins and serotonin. [GOC:dph, GOC:mtg_muscle, GOC:tb]

Neurotransmitter secretion is a crucial process for regulating skeletal muscle contraction. It involves a complex cascade of events that begin with an action potential traveling down a motor neuron to the neuromuscular junction, the specialized synapse between the motor neuron and the muscle fiber.

At the neuromuscular junction, the action potential triggers the opening of voltage-gated calcium channels at the presynaptic terminal of the motor neuron. This influx of calcium ions initiates a series of events that lead to the fusion of synaptic vesicles containing acetylcholine (ACh), a neurotransmitter, with the presynaptic membrane.

Fusion of the vesicles releases ACh into the synaptic cleft, the narrow gap between the presynaptic and postsynaptic membranes. ACh then diffuses across the cleft and binds to nicotinic acetylcholine receptors (nAChRs) located on the muscle fiber membrane.

Binding of ACh to nAChRs triggers a conformational change in the receptors, opening their ion channels and allowing sodium ions to flow into the muscle fiber. This influx of sodium ions depolarizes the muscle fiber membrane, generating an end-plate potential (EPP).

The EPP propagates along the muscle fiber membrane, triggering the release of calcium ions from the sarcoplasmic reticulum, a specialized intracellular organelle that stores calcium. The increase in intracellular calcium levels initiates a series of events that lead to the sliding of the actin and myosin filaments within the muscle fiber, resulting in muscle contraction.

Following ACh release, the neurotransmitter is rapidly removed from the synaptic cleft by the enzyme acetylcholinesterase (AChE). This hydrolysis of ACh prevents excessive stimulation of the muscle fiber and allows for relaxation.

In summary, neurotransmitter secretion at the neuromuscular junction is a tightly regulated process that involves the release of ACh, its binding to nAChRs, depolarization of the muscle fiber membrane, calcium release from the sarcoplasmic reticulum, and subsequent muscle contraction. Efficient removal of ACh from the synaptic cleft ensures proper muscle relaxation and prevents sustained contraction.'
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Proteins (1)

Compounds (5)