Question 1

Which of the following best describes the function of the transverse (T) tubules in skeletal muscle fibers?

Accepted Answer

They transmit electrical impulses from the sarcolemma deep into the muscle fiber.

Question 2

What is the primary role of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

To store and release calcium ions during muscle contraction.

Question 3

During muscle contraction, which of the following changes occur in the sarcomere?

Accepted Answer

The I band and H band both decrease in width.

Question 4

Which protein directly blocks the active sites on actin molecules in a resting muscle fiber?

Accepted Answer

Tropomyosin

Question 5

What triggers the exposure of active sites on actin, allowing cross-bridge formation?

Accepted Answer

Release of calcium ions from the sarcoplasmic reticulum

Question 6

A muscle fiber is described as multinucleate. What does this mean?

Accepted Answer

It contains hundreds of nuclei just beneath the sarcolemma.

Question 7

Which of the following best explains the sliding filament theory?

Accepted Answer

Thin filaments slide toward the center of the sarcomere alongside stationary thick filaments.

Question 8

Which structure marks the boundary between adjacent sarcomeres?

Accepted Answer

Z line

Question 9

What is the function of titin in the sarcomere?

Accepted Answer

It keeps thick and thin filaments aligned and provides elasticity.

Question 10

Which of the following statements about myofibrils is correct?

Accepted Answer

They are bundles of myofilaments that can actively shorten to produce contraction.

Question 11

A patient has a genetic defect that prevents the formation of functional troponin. Which of the following would most likely occur in their skeletal muscle fibers?

Accepted Answer

Tropomyosin would not move away from actin's active sites, preventing contraction.

Question 12

Which of the following best describes the role of mitochondria in skeletal muscle fibers?

Accepted Answer

They provide ATP required for muscle contraction.

Question 13

If the sarcolemma of a muscle fiber is damaged, which of the following processes would be most directly affected?

Accepted Answer

Transmission of electrical impulses into the muscle fiber

Question 14

Which of the following is true regarding the A band in a sarcomere during contraction?

Accepted Answer

The A band remains the same length.

Question 15

A researcher is studying a muscle fiber under a microscope and observes that the I bands are significantly reduced in width, but the A bands remain unchanged. What can be concluded about the state of the muscle fiber?

Accepted Answer

The muscle fiber is contracted.

Question 16

Which of the following best explains why skeletal muscle fibers are multinucleate?

Accepted Answer

They are formed by the fusion of multiple embryonic cells, resulting in many nuclei.

Question 17

Which of the following events occurs FIRST during the contraction of a skeletal muscle fiber?

Accepted Answer

Calcium ions are released from the sarcoplasmic reticulum.

Question 18

A patient with a vitamin D deficiency is likely to have impaired muscle contraction. Which of the following best explains why?

Accepted Answer

Vitamin D is necessary for calcium absorption, which is essential for muscle contraction.

Question 19

Which of the following best describes the role of the M line in the sarcomere?

Accepted Answer

It connects the central portions of each thick filament to its neighbors.

Question 20

During a muscle contraction, which of the following best describes the sequence of events involving calcium ions?

Accepted Answer

Calcium ions bind to troponin, causing a conformational change that moves tropomyosin and exposes active sites on actin.

Structural Organization and Function of Skeletal Muscle Fibers

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