NMJ, Excitation-Contraction Coupling, and the Sliding Filament Theory order of operation

1

An action potential travels down the motor neuron to the axon terminal

2

voltage gated calcium channels open in the neuron allowing ca2+ to enter the axon terminal

3

ACh is released into the synaptic cleft via exocytosis

4

ACh binds to receptors on the sarcolemma, triggering an action potential in the muscle

5

Acetylcholinesterase breaks down remaining ACh in the synaptic cleft

6

The action potential travels along the sarcolemma and deep into T tubules

7

Calcium is released from the sarcoplasmic reticulum into the sarcoplasm

8

Calcium ions bind to troponin causing tropomyosin to shift and expose active sites on actin

9

Myosin heads bind to the exposed active sites on actin forming a cross bridge

10

The myosin head preforms a power stroke pulling the actin filament toward the M-line

11

ATP binds to the myosin head causing it to detach from the actin filiament

12

ATP is hydrolyzed “re-cocking” the myosin head into it's high energy state