10 Steps of Muscle Contraction

Question 1

Step 1

Answer 1

Action potential starts in the brain

Question 2

Step 2

Answer 2

AP arrives at axon terminal, releases acetylcholine (ACh)

Question 3

Step 3

Answer 3

ACh crosses synapse, binds to ACh receptors on plasmalemma

Question 4

Step 4

Answer 4

AP travels down plasmalemma and T-tubules

Question 5

Step 5

Answer 5

Triggers calcium (Ca2+) release from sarcoplasmic reticulum (SR)

Question 6

Step 6

Answer 6

Ca2+ binds to troponin on thin actin filament

Question 7

Step 7

Answer 7

Troponin-Ca2+ complex moves tropomyosin revealing connecting point for myosin head

Question 8

Step 8

Answer 8

Myosin head connects to actin and pulls actin toward sarcomere center (the power stroke)

Question 9

Step 9

Answer 9

After power stroke ends, Myosin detaches from active site, head rotates back to original position, then attaches to another active site farther down the actin chain

Question 10

Step 10

Answer 10

Process continues until Z-disk reaches myosin filaments or AP stops and Ca2+ gets pumped back into the SR