Back to notes
How does the power stroke contribute to muscle contraction?
Press to flip
During the power stroke, the myosin head attaches to actin, moves to pull the actin filament, and releases ADP and phosphate, causing sarcomere shortening.
What structural feature gives skeletal muscle its striated appearance?
The arrangement of alternating thick (myosin) and thin (actin) filaments in sarcomeres gives skeletal muscle its striated appearance.
What distinguishes cardiac and smooth muscle tissues from skeletal muscle in terms of control?
Cardiac and smooth muscle tissues are under involuntary control, while skeletal muscle is under voluntary control.
Explain the function of cross bridges in the sliding filament model.
Cross bridges, formed by myosin heads, attach to actin filaments and change shape to slide the actin over the myosin during contraction.
What is the role of ATP in the power stroke?
ATP is hydrolyzed to ADP and phosphate to extend the myosin head; new ATP binding allows myosin to detach from actin and reset for another power stroke.
Describe the role of sarcomeres in muscle contraction.
Sarcomeres are the contractile units within myofibrils made of alternating thick and thin filaments, and they contract when these filaments slide past each other.
Define the role of the T-tubules in muscle contraction.
T-tubules conduct electrical impulses from the muscle fiber surface to the interior, facilitating the release of calcium ions from the sarcoplasmic reticulum.
Explain the sliding filament mechanism in terms of myofilament interaction.
In the sliding filament mechanism, myosin (thick filament) cross bridges attach to actin (thin filament) and pull them towards the M-line, causing sarcomere shortening and muscle contraction.
What happens to the sarcomere length during a muscle contraction?
The sarcomere shortens during muscle contraction as the actin and myosin filaments slide past each other.
Describe the relationship between myofibrils and muscle fibers.
Muscle fibers are composed of myofibrils, which contain the sarcomeres responsible for muscle contraction.
How do regulatory proteins control muscle contraction?
Tropomyosin blocks actin binding sites when the muscle is relaxed, and troponin binds to calcium ions, moving tropomyosin to expose sites for myosin binding and contraction.
How do the roles of actin and myosin differ in muscle contraction?
Actin serves as the track that myosin heads attach to and pull for contraction, while myosin is the motor that drives this action.
What is the significance of the M-line in muscle structure?
The M-line is the center of the sarcomere where myosin filaments are anchored and serves as a point of attachment during contraction.
What triggers the release of calcium from the sarcoplasmic reticulum?
Nerve signals lead to muscle fiber depolarization, causing calcium ion release from the sarcoplasmic reticulum, triggering contraction.
What is the function of a neuromuscular junction?
The neuromuscular junction is the site of signal exchange between the synaptic bulb of an axon terminal and a muscle fiber, initiating muscle contraction.
Previous
Next