18 Questions
What happens when Ca2+ binds to troponin in muscle contraction?
Troponin changes shape, exposing myosin binding sites on the thin filaments.
What initiates the cross bridge cycling in muscle contraction?
Myosin binding to actin.
What occurs when the muscle action potential ceases in terms of calcium levels?
Ca2+ is released from the SR to the cytosol.
What happens when Ca2+ levels are low in muscle contraction?
Tropomyosin blocks active sites on actin.
What leads to relaxation in muscle fibers during contraction?
Tropomyosin unblocking active sites.
What occurs each time an action potential arrives at the neuromuscular junction?
The voltage-sensitive tubule proteins change shape.
What happens when Ca2+ is absent in muscle contraction?
Relaxation occurs
During excitation-contraction (E-C) coupling, where does the action potential propagate?
Along the sarcolemma and T tubules
Which protein blocks active sites on actin in muscle contraction?
Tropomyosin
What leads to the sliding of myofilaments during muscle contraction?
Binding of troponin and myosin
In which step of excitation-contraction (E-C) coupling are calcium ions released?
From the terminal cistern of SR
What happens to myosin-actin interaction if tropomyosin is blocking the active sites?
It is inhibited
What is the role of ATP in muscle contraction?
ATP hydrolysis energizes the myosin head for cross bridge formation
How does higher intracellular calcium concentration contribute to muscle contraction?
Ca2+ binds to troponin, triggering a shift in tropomyosin, allowing myosin and actin interaction
What happens during the working (power) stroke in the cross bridge cycle?
Myosin heads pivot and pull thin filaments toward the center of the sarcomere
What is the function of tropomyosin in muscle contraction?
Tropomyosin blocks myosin-binding sites on actin filaments at rest
What causes cross bridge detachment in the sarcomere?
ADP and Pi bind to myosin heads, causing them to release from actin
In the context of muscle contraction, what does troponin do?
Troponin binds Ca2+ and triggers a conformational change in tropomyosin
Test your knowledge on the process of muscle contraction, including the role of Ca2+, troponin, myosin, actin, and cross bridge cycling. Understand how E-C coupling, Ca2+ release channels, and SR function during muscle contraction.
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