Muscle contraction steps

Question 1

Muscle contraction steps

Answer 1

1. ) action potential: reaches the muscle fiber
2. ) calcium release: Ca2+ is released
3. ) troponin activated: Ca2+ binds to troponin
4. ) tropomyosin released: troponin pulls tropomyosin off of myosin binding sites
   5) cross- bridge: myosin heads grab onto action cross-bridge forms
5. ) power stroke: myosin head pull actin inward
6. ) reset: myosin detaches from actin resets

Question 2

Step 1: Action Potential

Answer 2

ACh is released from the motor neuron and binds to receptors in the motor end plate—> end plate triggers an action potential

• which contracts the muscle at the neurotransmitter junction –> acetylecholrine is released and the muscle membrane
• AP goes down the membrane( depolarization )

Question 3

Step 2: Calcium release

Answer 3

• depolarizes of muscle cell membrane causes calcium release
• depolarization spreads into membrane regions called t-tubules—-> contract the SR
• calcium is released from the SR into the cytosol of the muscle cell

Question 4

step 3: troponin activated

Answer 4

calcium binds to troponin (causing a shape change) troponin unlocks and releases from tropomyosin

Question 5

Step 4: Tropomyosin releases

Answer 5

troponin moves tropomyosin off the myosin binding sites and frees actin

Question 6

Step 5: myosin binds to actin

Answer 6

• myosin binds to actin forming a cross bridge

Question 7

Step 6: myosin moves actin

Answer 7

• myosin heads move actin inward toward the M-line

- a movement called the power stroke (requires ATP)

Question 8

Step 7: myosin releases actin

Answer 8

• myosin detaches from actin and resets for the next contraction

Question 9

Step 8: Calcium returned to the SR

Answer 9

• calcium to SR—> stop the signal, reset calcium and prepare for the next contraction.