Answer:
The correct answer will be:
1. Acetylcholine binds to receptors on the motor end plate
2. Chemically-regulated ion channels open, causing depolarization
3 End plate potentials trigger action potential(s).
4. Transverse tubules convey potentials into the interior of the cell
5. Ca++ is released from the sarcoplasmic reticulum
6. Ca++ binds to troponin, pulling on tropomyosin
7. Binding sites on actin are uncovered, allowing myosin to bind and carry out power strokes
8. Force increases.
9. Ca++ is pumped (re-sequestered) into the sarcoplasmic reticulum
10. Force decreases.
Explanation:
The muscle contraction is a highly controlled mechanism which begins at the neuromuscular junction with the release of the acetylcholine neurotransmitter. This neurotransmitter causes the depolarization of the membrane by binding to the receptors of the motor end plate which generates an action potential. This action potential is transmitted via T-tubules from sarcolemma to the sarcoplasmic reticulum.
The sarcoplasmic reticulum releases calcium ions which binds to the troponin protein. This troponin removes the protein tropomyosin from the actin causing the rotation of the tropomyosin exposing the binding sites for myosin. The myosin binds to the actin using energy from the ATP which pulls the actin causing contraction. Another ATP binds the myosin head which weakens the bond between myosin and actin which releases the myosin which decreases the force between them decreases and the muscles relax.
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