Question 1

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

Accepted Answer

It stores and releases calcium ions, which are essential for initiating muscle contraction.

Question 2

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

Accepted Answer

The I bands and H bands narrow, while the A band remains constant in width.

Question 3

A patient is experiencing muscle weakness due to a lack of acetylcholinesterase (AChE) at the neuromuscular junction. What is the most likely physiological consequence?

Accepted Answer

Prolonged muscle contraction due to continuous stimulation by acetylcholine.

Question 4

Which connective tissue layer surrounds individual muscle fibers and contains capillaries and myosatellite cells?

Accepted Answer

Endomysium

Question 5

A muscle fiber is stimulated at a frequency greater than 50 times per second, and the next stimulus arrives before the previous relaxation phase is complete. What is this phenomenon called?

Accepted Answer

Wave summation

Question 6

Which of the following equations correctly represents the conversion of creatine phosphate (CP) to ATP during muscle contraction?

Accepted Answer

$$\mathrm{ADP} + \mathrm{CP} \xrightarrow{CK} \mathrm{ATP} + \mathrm{Creatine}$$

Question 7

Which type of skeletal muscle fiber is best adapted for endurance activities such as marathon running?

Accepted Answer

Slow fibers (Type I)

Question 8

A person is lifting a heavy box. Initially, the muscle develops tension but does not change length. What type of contraction is occurring at this stage?

Accepted Answer

Isometric contraction

Question 9

Which of the following best explains why cardiac muscle cells are highly resistant to fatigue?

Accepted Answer

They rely almost exclusively on aerobic metabolism and contain many mitochondria and myoglobin.

Question 10

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

Accepted Answer

Smooth muscle can contract even when greatly stretched due to its plasticity.

Question 11

A patient with Clostridium tetani infection is experiencing sustained, powerful muscle contractions. What is the physiological basis for this symptom?

Accepted Answer

The neurotoxin prevents the inhibition of motor neurons, resulting in continuous stimulation and complete tetanus.

Question 12

Which of the following best describes the function of titin in the sarcomere?

Accepted Answer

It acts as a molecular spring, helping to restore the sarcomere to its resting length after contraction.

Question 13

Which of the following statements about the length-tension relationship in skeletal muscle is correct?

Accepted Answer

Maximum tension is produced when the maximum number of cross-bridges can form at the optimal sarcomere length.

Question 14

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

Accepted Answer

Accumulation of lactic acid and hydrogen ions lowers pH, impairing enzyme activity and calcium binding.

Question 15

Which of the following is a correct sequence of events at the neuromuscular junction leading to muscle contraction?

Accepted Answer

Action potential arrives at axon terminal → ACh released → ACh binds to receptors on motor end plate → Na$$^+$$ influx → Action potential in sarcolemma

Question 16

Which of the following hormones increases the rate of energy consumption in both resting and active muscles?

Accepted Answer

Thyroid hormones

Question 17

A muscle is attached to a 2 kg weight and develops enough tension to lift it, causing the muscle to shorten while the tension remains constant. What type of contraction is this?

Accepted Answer

Isotonic concentric contraction

Question 18

Which of the following best describes the process of recovery after intense exercise?

Accepted Answer

Lactate is transported to the liver, converted to pyruvate, and then to glucose, which is returned to muscle (Cori cycle).

Question 19

Which of the following is a characteristic of cardiac muscle tissue but NOT skeletal muscle tissue?

Accepted Answer

Cells are connected by intercalated discs containing gap junctions and desmosomes.

Muscle Tissue: Structure, Function, and Physiology

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