skeletal muscle contraction

 Skeletal muscle contraction

Nerve impulse

Axon of motor neuron

Action potential activate Ca2+ ion channel gate on axon

Causing Ca2+ ion to flow into axon terminal

Increase Ca2+ ion concentration stimulates release of neurotransmitter acetylcholine from axon terminal to synaptic cleft.

Acetylcholine across synaptic cleft at neuromuscular junction and 

Bind to receptor site of motor end plate opening, channel in membrane for sodium (Na+) and K+ ion. (Channel protein in plasma membrane, transportation ion through channels)

Skeletal muscle fiber exited by large myelinated nerve fibers, which attach to the neuromuscular junction.

Na+ and K+ channel in plasma membrane of motor end plate open.

Na+ rushes in and potassium rashes out. 

(Flow of Na+ into muscle fiber greater than flow of  K+ out).

Resulting changes in Na+ and K+ ions causes depolarization at motor end plate.

Muscle fibre membrane become more positively charged, triggering action potential.

Action potential

Electrical change which take place when nerve conducts impulses or a muscle fiber contracts.

Action potential propagates over surface of entire muscle fibre and move into fibre along transverse tubules.

Action potential in transverse tubules cause release of Ca2+ ion from from sarcoplasmic reticulum; these ions stimulate myofibrils in muscle cell to contract.

Acetylcholinesterase enzyme found on muscle fibre membrane then break down acetylcholine into acetate and choline.

When receptor site no bound acetylcholine, membrane of motor end plate return into its resting potential.