BackSteps of Muscle Contraction quiz
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BackWhich of the following is the correct sequence of events for muscle contractions? a) Action potential, calcium release, cross-bridge formation, power stroke b) Calcium release, action potential, power stroke, cross-bridge formation c) Cross-bridge formation, power stroke, action potential, calcium release d) Power stroke, cross-bridge formation, calcium release, action potential
a) Action potential, calcium release, cross-bridge formation, power stroke Which of the following provides the final 'go signal' for muscle contraction? a) Acetylcholine b) Calcium ions c) ATP d) Sodium ions
b) Calcium ions During a muscle contraction, what role does ATP play?
ATP is required for the detachment of myosin heads from actin filaments and for the re-cocking of the myosin heads for another cycle of contraction. Where in the cross-bridge cycle does ATP hydrolysis occur?
ATP hydrolysis occurs after the myosin head detaches from the actin filament, providing energy to re-cock the myosin head for the next cycle. When does the sarcoplasmic reticulum release calcium?
The sarcoplasmic reticulum releases calcium in response to an action potential traveling down the T-tubules. Which is not a step of skeletal muscle contraction? a) Calcium binding to troponin b) Myosin binding to actin c) ATP binding to myosin d) Sodium binding to actin
d) Sodium binding to actin Which statement describes the mechanism of muscle contraction?
Muscle contraction involves the sliding of actin filaments over myosin filaments, powered by ATP and regulated by calcium ions. What triggers the release of calcium ions from the sarcoplasmic reticulum?
The release of calcium ions is triggered by an action potential traveling down the T-tubules. What are the 7 steps of muscle contraction?
1) Action potential arrives at neuromuscular junction 2) Acetylcholine is released 3) Action potential travels along sarcolemma 4) Calcium ions are released 5) Calcium binds to troponin 6) Cross-bridge cycle begins 7) Muscle contraction occurs Which of these events occurs first in muscle fiber contraction? a) Calcium binds to troponin b) Acetylcholine is released c) Myosin binds to actin d) ATP is hydrolyzed
b) Acetylcholine is released Which of the following occurs during the power stroke of muscle contraction?
During the power stroke, the myosin head pulls the actin filament towards the center of the sarcomere, releasing ADP and phosphate. During muscle contraction, what happens to the sarcomere?
During muscle contraction, the sarcomere shortens as actin filaments slide over myosin filaments. Which describes step three of a muscle contraction?
Step three involves the propagation of the action potential along the sarcolemma and into the T-tubules. How do calcium ions initiate contraction in skeletal muscle fibers?
Calcium ions bind to troponin, causing a conformational change that moves tropomyosin away from myosin-binding sites on actin, allowing cross-bridge formation. During a skeletal muscle contraction, what is the role of troponin?
Troponin binds calcium ions, which causes a shift in tropomyosin to expose myosin-binding sites on actin filaments. Which of the following events triggers the subsequent steps of excitation-contraction coupling? a) Release of acetylcholine b) Binding of calcium to troponin c) Action potential in the T-tubules d) Hydrolysis of ATP
c) Action potential in the T-tubules Which of the following statements about muscle contraction is true? a) ATP is not required for muscle contraction b) Calcium ions are not involved in muscle contraction c) Muscle contraction involves the sliding of actin over myosin d) Acetylcholine is not necessary for muscle contraction
c) Muscle contraction involves the sliding of actin over myosin Which step constitutes the power stroke of muscle contraction?
The power stroke occurs when the myosin head pivots and pulls the actin filament towards the center of the sarcomere. Which is the correct order of events in a contraction? a) Calcium release, cross-bridge formation, power stroke, ATP binding b) Cross-bridge formation, ATP binding, power stroke, calcium release c) Power stroke, calcium release, cross-bridge formation, ATP binding d) ATP binding, power stroke, calcium release, cross-bridge formation
a) Calcium release, cross-bridge formation, power stroke, ATP binding What role do calcium and ATP play in muscle contraction?
Calcium ions bind to troponin to expose myosin-binding sites on actin, while ATP provides energy for cross-bridge cycling and myosin head detachment. Which is not a step of skeletal muscle contraction? Multiple choice question. a) Calcium binding to troponin b) Myosin binding to actin c) ATP binding to myosin d) Sodium binding to actin
d) Sodium binding to actin Which of the following steps of the crossbridge cycle occurs immediately before the power stroke? a) ATP binding to myosin b) Myosin head binding to actin c) Release of ADP and phosphate d) Calcium binding to troponin
b) Myosin head binding to actin What is the first event in muscle fiber contraction?
The first event in muscle fiber contraction is the release of acetylcholine at the neuromuscular junction, which initiates an action potential in the muscle fiber.
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