Arrange the events in their proper sequence at the NMJ

Question

A. myosin forms cross bridges with Actin

B. Ach released, crosses synaptic gap, and bonds to Na+ ligand gate

C. Ca++ released and binds to Troponin, which cause a change in the shape of Tropomyosin, which unblocks the actin cross bridge sites

D. Na+ gates open, Na+ rushes into fiber causing charge to become positive

E. At rest, Ach is stored in synaptic bulb, Tropomyosin blocks actin cross bridge sites, all gates are closed

F. Troponin changes back to original shape, result is Tropomyosin reblocking sites

G. Binding sites are blocked, so contraction stops

H. Ca++ reuptaken into sarcoplasmic reticulum, Ca++ comes off Troponin

Answer 1

Hi Alexys,

The answer is the following: E, B, D, C, A, H, F, G

In resting cell, it first starts with an action potential reaching the neuron at NMJ, which makes neuron release neurotransmitters (ACh). Ach diffuses across to stimulate Ca2+ release in the muscle cell from sarcoplasmic reticulum. Then Ca2+ bind to troponin and remove tropomyosin from the myosin. Then myosin heads can bind actin to begin the myosin actin contraction cycles, and stop when there is no more Ca2+ to unblock tropomyosin from myosin.

Hope that helps!