What Is Neuromuscular Junction?

Neuromuscular junction is the site the motor neuron and muscle fiber meet. Nerve impulse gets to the axon terminal of the motor neuron and release acetylcholine. Acetylcholine diffuses across the synaptic cleft and binds to the receptors in the motor end plate and starts a muscle action potential. Acetylcholinesterase in the synaptic cleft destroys ach so another muscle action potential does not arise unless more ach is released from motor neuron. Muscle action potential travelling along transverse tubule opens, calcium release channels in the sarcoplasmic reticulum membrane, which allows calcium ions to overflow into sarcoplasm. Calcium binds to troponin on the thin filament (actin), exposing the binding sites for myosin. Reduction power strokes
use ATP, myosin heads bind to actin, rotate, and release, thin filaments are pulled towards center of sarcomere. Calcium release channels in sarcoplasmic reticulum close and calcium active transport pumps use ATP to restore low levels of calcium in sarcoplasm. Troponin-tropomyosin complex slides back into position where it blocks the myosin binding sites on actin. Muscle relaxes.