Question 1

Which of the following best describes the main function of the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

It stores and releases Ca$$^{2+}$$ ions necessary for muscle contraction.

Question 2

A patient is experiencing muscle weakness due to a defect in acetylcholine (ACh) receptors at the neuromuscular junction. Which step in muscle contraction is most directly affected?

Accepted Answer

Depolarization of the motor end plate

Question 3

Which connective tissue sheath surrounds an individual muscle fiber?

Accepted Answer

Endomysium

Question 4

During a high-intensity sprint lasting 10 seconds, which energy source is primarily used by skeletal muscle fibers?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate (CP)

Question 5

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

Accepted Answer

Branching cells with intercalated discs

Question 6

A muscle fiber is unable to relax after contraction, resulting in a state similar to rigor mortis. What is the most likely cause?

Accepted Answer

Lack of ATP to detach myosin heads from actin

Question 7

Which of the following best explains why smooth muscle can maintain contraction for long periods with minimal energy expenditure?

Accepted Answer

Myofilaments latch together, reducing ATP consumption

Question 8

Which of the following is true regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Maximum force is generated when the muscle is at optimal resting length

Question 9

A motor unit consists of:

Accepted Answer

A single motor neuron and all the muscle fibers it innervates

Question 10

Which of the following best describes the process of temporal summation in muscle contraction?

Accepted Answer

Increasing the frequency of stimulation to produce greater force

Question 11

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

Accepted Answer

Myosin heads bind to actin, pulling thin filaments toward the M line

Question 12

Which of the following is the correct sequence of events for excitation-contraction coupling in skeletal muscle?

Accepted Answer

Action potential on sarcolemma → Ca$$^{2+}$$ release from SR → Ca$$^{2+}$$ binds troponin → Cross-bridge formation

Question 13

Which of the following best explains why muscle fatigue occurs during prolonged, intense exercise?

Accepted Answer

Ionic imbalances and accumulation of inorganic phosphate interfere with Ca$$^{2+}$$ regulation

Question 14

Which of the following is a function of muscle tone?

Accepted Answer

Maintaining posture and stabilizing joints

Question 15

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

Accepted Answer

They transmit action potentials deep into the muscle fiber to ensure simultaneous contraction

Question 16

Which of the following is true regarding the regeneration of muscle tissue?

Accepted Answer

Smooth muscle has a greater capacity for regeneration than skeletal muscle

Question 17

A muscle is attached to a bone via a tendon. Which type of attachment is this?

Accepted Answer

Indirect attachment

Question 18

Which of the following best explains why cardiac muscle cells are able to contract in a coordinated manner?

Accepted Answer

They are connected by gap junctions at intercalated discs

Question 19

Which of the following is a distinguishing feature of smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle lacks striations and has a single, centrally located nucleus

Question 20

Which of the following best describes the 'size principle' of motor unit recruitment?

Accepted Answer

Motor units with the smallest fibers are activated first, followed by larger ones as more force is needed

Muscle Tissue: Structure, Function, and Physiology

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