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A 23-year-old track runner comes to your office complaining of lower extremity pain. The pain is localized to the right lower hamstrings. The patient sensed the pain immediately after completing a 1-mile sprint. Which of the following statements is true regarding muscle fibers?
A Cardiac muscle does not have actin and myosin organized into sarcomers.
B Red muscle fibers have a large mass per motor unit.
C Skeletal cells have limited sarcoplasmic reticulum.
D Smooth muscles have high ATPase activity.
E White muscles have a high capacity for anaerobic glycolysis

e?

d????

eee

eee

yes E weldone

A Cardiac muscle does not have actin and myosin organized into sarcomers. Cardiac muscle does have sarcomers, and they determine the Frank-Starling mechanism.
B Red muscle fibers have a large mass per motor unit. Red muscle fibers have a small mass per motor unit because they typically belong to muscles that do not require less power.
C Skeletal cells have limited sarcoplasmic reticulum. These muscle fibers typically have extensive sarcoplasmic reticulum because the calcium needs to bind to troponin to activate the muscle fiber.
D Smooth muscles have high ATPase activity. Smooth muscles have low ATPase activity. Cardiac and skeletal muscles have a higher ATPase activity because they are involved in more rigorous work.
E White muscles have a high capacity for anaerobic glycolysis. White muscles have a high capacity because they are used as large, powerful muscles in short-term bursts of activity

EE