Question 1

Which of the following best describes the function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

A patient is diagnosed with a genetic disorder that affects the dystrophin protein. Which of the following is the most likely consequence in skeletal muscle?

Accepted Answer

Impaired transmission of force from myofibrils to the sarcolemma, leading to muscle weakness.

Question 3

Which of the following statements about the sliding filament model of contraction is correct?

Accepted Answer

During contraction, myosin heads bind to actin and pull thin filaments toward the center of the sarcomere.

Question 4

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

Accepted Answer

They are formed by the fusion of multiple myoblasts during development.

Question 5

A muscle fiber is stimulated to contract. Which sequence of events occurs first?

Accepted Answer

Binding of acetylcholine to receptors on the sarcolemma.

Question 6

Which of the following is a unique characteristic of cardiac muscle tissue compared to skeletal muscle tissue?

Accepted Answer

It can contract without nervous system stimulation.

Question 7

A muscle is attached to two bones. The attachment to the immovable bone is called the:

Accepted Answer

Origin

Question 8

Which of the following best describes the role of tropomyosin in muscle contraction?

Accepted Answer

It blocks the myosin-binding sites on actin in a relaxed muscle.

Question 9

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

Accepted Answer

The I band shortens, but the A band remains the same length.

Question 10

Which of the following is NOT a function of muscle tissue?

Accepted Answer

Production of hormones

Question 11

A researcher is studying the effect of calcium ion concentration on muscle contraction. Which equation best represents the relationship between calcium ion concentration ($$[\mathrm{Ca$$^{2+}$$}]) $$and the force of contraction ($$F) in $$skeletal muscle, assuming a direct proportionality?

Accepted Answer

$$F = k \cdot [\mathrm{Ca$$^{2+}$$}]$$

Question 12

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

Accepted Answer

They conduct action potentials deep into the muscle fiber to trigger calcium release.

Question 13

A patient presents with muscle weakness and is found to have a defect in acetylcholine receptors. Which process is most directly impaired?

Accepted Answer

Initiation of action potentials in the sarcolemma.

Question 14

Which of the following is true regarding the elastic filament in muscle fibers?

Accepted Answer

It is composed of titin and helps the muscle fiber recoil after stretching.

Question 15

Which of the following best explains why smooth muscle can contract even when nervous system stimulation is absent?

Accepted Answer

Smooth muscle can be stimulated by hormones and local chemical signals.

Question 16

Which of the following structures is responsible for the striated appearance of skeletal muscle fibers?

Accepted Answer

The regular arrangement of thick and thin filaments into sarcomeres.

Question 17

A muscle fiber is unable to relax after contraction. Which of the following is the most likely cause?

Accepted Answer

Failure to remove calcium ions from the cytosol back into the sarcoplasmic reticulum.

Question 18

Which of the following best describes the relationship between the number of motor units activated and the force produced by a skeletal muscle?

Accepted Answer

The more motor units that are stimulated, the greater the force produced.

Question 19

Which of the following is the smallest contractile unit of a skeletal muscle fiber?

Accepted Answer

Sarcomere

Question 20

Which of the following best explains why skeletal muscle fibers require a rich blood supply?

Accepted Answer

To deliver oxygen and nutrients and remove metabolic wastes generated during contraction.

Muscles and Muscle Tissue: Structure and Function

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