Anatomy Tutorials by NEENA.

A little something on the

THE NEUROMUSCULAR JUNCTION
15 basic steps
1. The action potential arrives at the NEURO-MUSCULAR junction.
2. Calcium enters the presynaptic nerve terminal
3. Magnesium moves out
4. The Acetylcholine laden vesicles fuse with the presynaptic membrane
5. Acetylcholine is released then into the synaptic cleft of the neuromuscular junction through exocytosis
6. 2 Acetylcholine molecules bind to the NICOTINIC Acetylcholine receptor
7. At least 25-30% binding is needed
8. An END PLATE POTENTIAL is generated which moves across the sarcolemma and percolates the muscle cell through the T-tubule
9. The DIHYDROPYRIDINE receptor on the T-tubule then STIMULATES the RYANODINE receptor on the intracellular SARCOPLASMIC RETICULUM
10. The CALCIUM is then released from the SARCOPLASMIC RETICULUM and moves into the SARCOMERE
11. It unlocks the TROPOMYOSIN cable from ACTIN exposing the active subunit
12. The MYOSIN head is simultaneously charged into position by ATP
13. MYOSIN binds to ACTIN
14. CONTRACTION OCCURS
15. The MUSCLE SHORTENS

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