Neuromuscular Junction

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What are the four steps of action potential?

What are the four steps of action potential?

Resting State, Depolarization, Re-polarization and Na+/K+ pump

what is Resting State?

Na+ outside and K+ inside (salty banana).

In this graph case, Cytosol has a slightly negative charge

what is depolarization?

Change in the resting potential.

In this case it is the Influx of Na+ ions into the neuron.

what is Re-polarization?

Restoring balance.

In an attempt to restore balance, K+ moves out of the neuron into the interstitial fluid.

What is Na+/K+ pump?

A pump that transports ions form low to high concentration. It requires energy.

In this case, Na+ and K+ ions are transported across the membrane against the concentration gradient to return ion levels to normal

What is Neuromusclar Junction?

a place where action potential happens and causes release of neurotransmitters.

What is the first step that happens in Neuromuscular Junction?

Action potential is sent along a neuron to the axon terminal

Second step in Neuromuscular Junction

The AP causes voltage gated Ca2+ channels to open up allowing extracellular calcium to flood into the axon terminal

Third step in neuromuscular junction

Ca2+ causes vesicles containing the neurotransmitter acetylcholine (ACh) to fuse with the membrane of the axon terminal and to release ACh into the synaptic cleft

fourth step in neuromuscular junction

ACh drifts through the synaptic cleft and binds with Na+ channels causing the channels to open and allow Na+ to flow into the cell and continue the action potential

fifth step in neuromuscular junction

Once the AP has continued the enzyme acetylcholinesterase (ACh-ase) will begin to breakdown excess ACh into the components acetic acid and choline

sixth step in neuromuscular junction

Acetic acid is transported to the blood as a waste product while choline is moved via active transport back into the axon terminal where it will combine with new acetic acid forming ACh and will be stored in a vesicle.

True or False: The vesicles containing ACh merge with the cell membrane of the neuron while the receptor sites for ACh are found on the cell membrane of the muscle.

True