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Questions and Answers
What initially stimulates muscle fibers upon receiving a message from motor neurons?
What initially stimulates muscle fibers upon receiving a message from motor neurons?
- A neurotransmitter
- Calcium ions
- An impulse (correct)
- ATP hydrolysis
Myofibrils are composed of sarcomeres, which are the fundamental contractile units of muscle fibers.
Myofibrils are composed of sarcomeres, which are the fundamental contractile units of muscle fibers.
True (A)
During muscle contraction, what ion is crucial for initiating the interaction between actin and myosin?
During muscle contraction, what ion is crucial for initiating the interaction between actin and myosin?
calcium
The binding of myosin to actin forms a ______ which is essential for muscle contraction.
The binding of myosin to actin forms a ______ which is essential for muscle contraction.
Match the events with the appropriate stage in muscle contraction:
Match the events with the appropriate stage in muscle contraction:
Which of the following explains how muscle fibers shorten during contraction?
Which of the following explains how muscle fibers shorten during contraction?
During muscle contraction, the cross-sectional area of the muscle decreases as sarcomeres clump together.
During muscle contraction, the cross-sectional area of the muscle decreases as sarcomeres clump together.
What molecule provides the energy for the power stroke during muscle contraction?
What molecule provides the energy for the power stroke during muscle contraction?
After the power stroke, ______ releases energy, causing myosin to detach and the crossbridge to break.
After the power stroke, ______ releases energy, causing myosin to detach and the crossbridge to break.
After contraction, how does a muscle return to its relaxed state?
After contraction, how does a muscle return to its relaxed state?
Flashcards
Myofibrils
Myofibrils
Long strands that make up muscle fibers, containing the contractile units.
Sarcomeres
Sarcomeres
Contractile units within muscle fibers containing actin and myosin.
Actin and Myosin
Actin and Myosin
Two myofilaments found in sarcomeres that are essential for muscle contraction.
Muscle Contraction Initiation
Muscle Contraction Initiation
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Crossbridge
Crossbridge
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Role of ATP in Contraction
Role of ATP in Contraction
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Power Stroke
Power Stroke
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Muscle Fiber Shortening
Muscle Fiber Shortening
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Muscle Relaxation
Muscle Relaxation
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Study Notes
- When a muscle contracts, a series of processes takes place.
- The message is sent from the brain to the muscle via a motor neuron.
- Motor neurons stimulate their corresponding motor units with an impulse.
- Muscle fibers consist of long strands called myofibrils.
- Myofibrils contain the sarcomeres, the basic contractile units of the muscle.
- Sarcomeres contain two myofilaments, called actin and myosin, which are essential for crossing over.
- When contraction occurs, calcium enters the sarcomere and stimulates the actin, revealing the binding sites for myosin heads to attach.
- Myosin attaches to actin to create a crossbridge.
- ATP is broken down, releasing energy that stimulates the crossbridges.
- Myosin pulls on the actin with a power stroke that pulls the actin towards the middle of the sarcomere.
- The muscle fiber shortens as the z-lines are pulled closer and the H and I zones disappear.
- Shortening causes the muscle fiber to contract, which results in the whole muscle contracting.
- When this happens, the sarcomeres are clumped together and the cross-sectional part of the muscle increases in size.
- ATP releases energy causing the myosin to detach.
- The crossbridge is broken and calcium leaves the sarcomere.
- The muscle returns to normal length and size in a relaxed state.
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Description
A message is sent from the brain to the muscle via a motor neuron. Myosin attaches to actin to create a crossbridge. Myosin pulls on the actin with a power stroke that pulls the actin towards the middle of the sarcomere.
