Neuromuscular junction

Nueromuscular junction

interation of neurons and muscle fibers at motor endpoint; triggers action potential

Action potential

nerve impulses for communication between cells

What is ACh?

Acetylcholine

Step 1 of NMJ

vesicles containing ACh reach membrane of synapse and releases ACh between synapse and sarcolema

Step 2 of NMJ

ACh binds to ACh receptors on sarcolema

Step 3 of NMJ

receptors open and sodium enters muscle fiber to generate action potential

Step 4 of NMJ

action potential reaches T-tubules, activating sarcoplasmic reticulum that releases calcium into cytoplasm

Step 5 of NJM

calcium binds to troponin on actin filament; releases tropomyosin that blocks myosin binding sites

Step 6 of NJM

ATP is hydrolized and begins contraction cycle of myosin

Step 7 of NJM

If ATP and calcium are present; sarcomere still contracts; if one or the other is depleted, it will relax

Step 8 of NJM

another neuron interacts with muscle fibers to inhibit more contraction by preventing ACh transfer, closing ACh receptors, preventing more action potentials

Step 9 of NJM

SR stops releasing calcium; lowers concentration in cytoplasm

Step 10 of NJM

Troponin unbinds to calcium and rebinds to tropomyosin, blocking myosin binding that leads to relaxsation

Step 11 of NJM

titin pulls Z-discs apart and returns them to original position