11 Steps for Muscle Contraction

Step 1

(From brain) action potential travels down motor neuron

Step 3

ACh diffuses across the synaptic cleft which opens the sodium channels

Step 10

ATP reattaches to myosin and breaks cross bridges

Step 5

Action potential stimulates release of Calcium from sarcoplasmic reticulum

Step 2

At the neuromuscular junction (NMJ), the action potential reaches the axon terminal and stimulates the release of Acetylcholine (ACh)

Step 6

Calcium binds to troponin which changes its shape

Step 11

Calcium is reabsorbed by sarcoplasmic reticulum- muscle relaxes ( because the troponin changes shape again -tropomyosin blocks binding sites)

Step 8

Myosin binds to actin (cross bridges) (along with ATP)

Step 9

Power stroke (movement of actin filaments towards middle of sarcomere)

Step 4

Sodium channels in sarcolemma (muscle cell membrane) carry action potential to T-tubules

Step 7

The troponin's change in shape moves tropomyosin from blocking the myosin binding sites on actin