Question 1

Which of the following best describes the role of the sarcoplasmic reticulum in skeletal muscle contraction?

Accepted Answer

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

Question 2

A patient is experiencing muscle weakness due to a lack of acetylcholine at the neuromuscular junction. Which step in the muscle contraction process is most directly affected?

Accepted Answer

Generation of an action potential in the muscle fiber membrane.

Question 3

Which of the following correctly matches the connective tissue layer with its location in skeletal muscle?

Accepted Answer

Perimysium surrounds fascicles, which are bundles of muscle fibers.

Question 4

During the contraction cycle, what is required for the myosin head to detach from actin after the power stroke?

Accepted Answer

Binding of ATP to the myosin head.

Question 5

Which ion rushes into the muscle cell when acetylcholine binds to receptors at the motor endplate, leading to depolarization?

Accepted Answer

Sodium ions ($$\mathrm{Na^+})$$

Question 6

A muscle fiber is observed to have multiple nuclei, is striated, and contracts rapidly but fatigues quickly. Which type of muscle fiber is this most likely to be?

Accepted Answer

Fast glycolytic (FG) fiber

Question 7

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

ATP is no longer produced, so myosin heads cannot detach from actin.

Question 8

Which of the following is true regarding the difference between isometric and isotonic muscle contractions?

Accepted Answer

Isometric contractions generate tension without changing muscle length, while isotonic contractions change muscle length.

Question 9

A muscle responsible for fine motor control, such as those controlling eye movement, is likely to have which characteristic?

Accepted Answer

A low number of muscle fibers per motor unit.

Question 10

Which hormone is primarily responsible for stimulating muscle growth (hypertrophy) in adults?

Accepted Answer

Testosterone

Question 11

Which of the following best describes the sequence of events during skeletal muscle contraction?

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release → exposure of actin → cross-bridge formation → power stroke → cross-bridge detachment

Question 12

Which of the following statements about actin and myosin is correct?

Accepted Answer

Actin forms the thin filaments, while myosin forms the thick filaments in the sarcomere.

Question 13

A muscle twitch is best defined as:

Accepted Answer

A single, brief contraction and relaxation cycle in a muscle fiber.

Question 14

Which of the following is a correct statement about smooth muscle?

Accepted Answer

It is found in the walls of hollow organs and is responsible for involuntary movements.

Question 15

Which of the following best describes the function of satellite cells in skeletal muscle?

Accepted Answer

They act as stem cells for muscle fiber repair and regeneration.

Question 16

A marathon runner's leg muscles are primarily composed of which type of muscle fiber, and what is a key characteristic of these fibers?

Accepted Answer

Slow oxidative (SO) fibers; high resistance to fatigue due to aerobic metabolism.

Question 17

If a muscle fiber is unable to release calcium ions from the sarcoplasmic reticulum, which step in the contraction cycle will be directly impaired?

Accepted Answer

Exposure of actin binding sites for myosin.

Question 18

Which of the following best explains why gross motor muscles, such as those in the thigh, have a high muscle fiber to motor unit ratio?

Accepted Answer

They require powerful contractions rather than precise control.

Question 19

A patient is diagnosed with a disorder that prevents ATP hydrolysis in muscle fibers. Which of the following would most likely occur during muscle contraction?

Accepted Answer

Myosin heads would not be able to pivot and perform the power stroke.

Question 20

Which of the following best describes the difference between fast oxidative-glycolytic (FOG) fibers and fast glycolytic (FG) fibers?

Accepted Answer

FOG fibers have greater resistance to fatigue and utilize both aerobic and anaerobic metabolism, while FG fibers fatigue quickly and rely mainly on anaerobic metabolism.

Skeletal Muscle Structure and Function: Study Guide for BIO 1121, Chapter 10

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