Question

Question 28 4 pts

Once the action potential occurs in the sarcolemma, it spreads moving down the T-tubules. What next? What is the correct order of events which result in skeletal muscle contraction? (4 points)

a. Once the muscle cell action potential is initiated then calcium ions are released from the sarcoplasmic reticulum. These calcium ions bind to troponin. With this binding, tropomyosin is pulled away from the active sites on actin. Myosin can bind with actin forming a cross bridge. A power stroke occurs, and the myofilaments (actin and myosin) move towards the center of the sarcomere. Muscle contraction ends when the calcium ions are pumped back into the sarcoplasmic reticulum

b. Once the muscle cell action potential is initiated, calcium ions are pumped back into the sarcoplasmic reticulum. These calcium ions bind to tropomyosin. With this binding, troponin is pulled away from the active sites on actin. Myosin can bind with actin forming a cross bridge. A power stroke occurs, and the myofilaments (actin and myosin) move towards the center of the sarcomere. The power stroke occurs releasing the neurotransmitter.

c. when the muscle cell action potential occurs, calcium ions are released from the sarcoplasmic reticulum. The calcium ions bind to troponin. This pulls tropomyosin away from the binding sites on myosin. Actin can bind with myosin forming a cross bridge. The myofilaments (actin and myosin) move away from the center of the sarcomere during the power stroke.

Answer 1

Answer=

Once the action potential occurs in the sarcolemma, it spreads moving down the T-tubules. The correct order of events which result in skeletal muscle contraction is

a. Once the muscle cell action potential is initiated then calcium ions are released from the sarcoplasmic reticulum.

These calcium ions bind to troponin. With this binding, tropomyosin is pulled away from the active sites on actin. Myosin can bind with actin forming a cross bridge. A power stroke occurs, and the myofilaments (actin and myosin) move towards the center of the sarcomere. Muscle contraction ends when the calcium ions are pumped back into the sarcoplasmic reticulum

Explanation - the sequence of events occurs during skeletal muscle contraction are as follows:

1. Once the muscle cell action potential is initiated.

2. then calcium ions are released from the sarcoplasmic reticulum.

3. These calcium ions bind to troponin.

4.With this binding, tropomyosin is pulled away from the active sites on actin.

5.Myosin can bind with actin forming a cross bridge.

6.A power stroke occurs, and the myofilaments (actin and myosin) move towards the center of the sarcomere.

7.Muscle contraction ends when the calcium ions are pumped back into the sarcoplasmic reticulum