Number the following events of skeletal muscle contraction in the proper order,

Question

Number the following events of skeletal muscle contraction in the proper order, with number 1 for the first event and number 9 for the last event. Actin binds to the myosin head, and a power stroke occurs as ADP and P, dissociate from myosin. The terminal cisternae of the sarcoplasmic reticulum release calcium ions into sarcoplasm because of the action potential. The sarcoplasmic reticulum removes calcium ions from the sarcoplasm, and tropomyosin returns to its origin position. The energy from ATP hydrolysis "cocks" the myosin crossbridge into an upright position. Acetylcholinesterase degrades acetylcholine in the synaptic cleft. Calcium ions bind to troponin, which pulls tropomyosin away from actin. Acetylcholine binds to receptors on the motor end plate and opens cation channels. ATP binds and causes the actin and myosin to dissociate from one another, after which it is hydrolyzed and myosin is recocked. The cycle repeats. Sodium ions flood the sarcoplasm and initiate an action potential that spreads along the sarcolemma and into the muscle fiber along the T-tubules.

Explanation / Answer

Events Step 6 Actin binds to the myosin head, and a power stroke occurs as ADP and Pi dissociate from myosin.

Events Step 3 The terminal cisternae of the sarcoplasmic reticulum release calcium ions into the sarcoplasm because of the action potential.

Step 9 The sarcoplasmic reticulum removes calcium ions from the sarcoplasm, and tropomyosin returns to its original position.

Step 5 The energy from ATP hydrolysis "cocks" the myosin cross-bridge into an upright position.

Step 8 Acetylcholinesterase degrades acetylcholine in the synaptic cleft.

Step 4 Calcium ions bind to troponin, which pulls tropomyosin away from actin.

Step 1 Acetylcholine binds to receptors on the motor end plate and opens cation channels.

Step 7 ATP binds and causes the actin and myosin to dissociate from one another, after which it is hydrolyzed and myosin is recocked. The cycle repeats.

Step 2 Sodium ions flood the sarcoplasm and initiate and action potential that spreads along the sarcolemma and into the muscle fiber along the T-tubules.  

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