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Questions and Answers
What occurs in Step 1 of muscle contraction?
What occurs in Step 1 of muscle contraction?
- Myosin and actin bind
- Acetylcholine is released
- Nerve impulse reaches neuromuscular junction (correct)
- Sodium channels open
What neurotransmitter is released by the motor neuron in Step 2?
What neurotransmitter is released by the motor neuron in Step 2?
Acetylcholine (ACH)
In Step 3, ACH binds to muscle receptor sites.
In Step 3, ACH binds to muscle receptor sites.
True (A)
What happens to sodium channels in Step 4?
What happens to sodium channels in Step 4?
What creates the action potential in Step 5?
What creates the action potential in Step 5?
The action potential travels down the muscle cell in Step 6.
The action potential travels down the muscle cell in Step 6.
What does the release of Ca++ cause in Step 7?
What does the release of Ca++ cause in Step 7?
How do Ca++ ions influence myosin and actin in Step 8?
How do Ca++ ions influence myosin and actin in Step 8?
What does the myosin do during contraction in Step 9?
What does the myosin do during contraction in Step 9?
What happens when the action potential ends in Step 10?
What happens when the action potential ends in Step 10?
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Study Notes
Steps of Muscle Contraction
- Nerve Impulse reaches the neuromuscular junction, triggering muscle activation.
- Motor neuron releases Acetylcholine (Ach), a neurotransmitter, into the synaptic gap, facilitating communication between nerve and muscle cells.
- Ach binds to muscle receptor sites, initiating the muscle contraction process.
- Binding of Ach stimulates receptors, leading to the opening of sodium (Na+) channels in the muscle cell membrane.
- Influx of Na+ ions alters the cell's polarity, generating an electrical current known as an Action Potential.
- The Action Potential travels along the sarcolemma, spreading across the muscle fiber to initiate contraction.
- The Action Potential triggers the sarcoplasmic reticulum to release stored calcium ions (Ca++) into the muscle cell and surrounding sarcomeres.
- Increased Ca++ levels enable myosin heads to attach to actin filaments within the sarcomeres, forming cross-bridges essential for contraction.
- Myosin heads pull actin filaments towards the center of the sarcomere, resulting in sarcomere shortening and muscle contraction.
- When the Action Potential ceases, Ca++ is reabsorbed by the sarcoplasmic reticulum, allowing myosin and actin to return to their original positions, leading to muscle relaxation.
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