Question 1

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

Accepted Answer

It stores and releases calcium ions necessary for muscle contraction.

Question 2

A patient is diagnosed with Duchenne Muscular Dystrophy (DMD). Which of the following is a direct consequence of this disease at the cellular level?

Accepted Answer

Disruption of the structural proteins that anchor myofibrils to the sarcolemma, leading to muscle fiber degeneration.

Question 3

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

Accepted Answer

The I band and H zone both narrow, while the A band remains unchanged.

Question 4

Which property of muscle cells allows them to return to their original length after being stretched?

Accepted Answer

Elasticity

Question 5

A toxin blocks the release of acetylcholine at the neuromuscular junction. What is the most likely effect on skeletal muscle contraction?

Accepted Answer

Muscle contraction will not occur because the muscle fiber will not be depolarized.

Question 6

Which of the following best explains why smooth muscle can contract up to 80% of its resting length, while skeletal muscle can only contract 30–40%?

Accepted Answer

Smooth muscle filaments are arranged obliquely and lack sarcomeres, allowing greater shortening.

Question 7

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

Accepted Answer

Pumping blood throughout the body by producing the beating of the heart.

Question 8

A muscle fiber is stimulated repeatedly at a high frequency, resulting in a sustained contraction with no visible relaxation. What is this phenomenon called?

Accepted Answer

Fused tetanus

Question 9

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

Accepted Answer

It binds calcium ions, causing tropomyosin to move and expose actin active sites.

Question 10

A patient is exposed to botulinum toxin, which prevents acetylcholine release at the neuromuscular junction. Which of the following symptoms would you expect?

Accepted Answer

Flaccid paralysis of skeletal muscles

Question 11

Which of the following equations correctly represents the relationship between force, cross-sectional area, and muscle tension?

Accepted Answer

$$F = \sigma \cdot A$$

Question 12

Which of the following best explains the 'latch state' in smooth muscle contraction?

Accepted Answer

It is a state where the muscle remains contracted with minimal ATP consumption.

Question 13

During the crossbridge cycle, what event directly causes the power stroke?

Accepted Answer

Release of ADP and inorganic phosphate from the myosin head

Question 14

Which of the following is true regarding the arrangement of myofilaments in smooth muscle compared to skeletal muscle?

Accepted Answer

Smooth muscle filaments are arranged obliquely and anchored to dense bodies, not sarcomeres.

Question 15

Which of the following best describes the function of the Z disc in a sarcomere?

Accepted Answer

It anchors thin filaments and serves as an attachment point for elastic filaments.

Question 16

A muscle fiber is stretched to twice its resting length before stimulation. What is the most likely effect on the tension it can generate?

Accepted Answer

Tension will be greatly reduced because there is minimal overlap between thick and thin filaments.

Question 17

Which of the following is a unique feature of cardiac muscle cells compared to skeletal muscle cells?

Accepted Answer

Presence of intercalated discs for electrical and mechanical connection.

Question 18

Which of the following best describes the role of the Na+/K+ pump in muscle fibers?

Accepted Answer

It maintains the resting membrane potential by moving 3 Na+ out and 2 K+ into the cell.

Question 19

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

Accepted Answer

Action potential in sarcolemma → T-tubule depolarization → Ca$$^{2+}$$ release from SR → Crossbridge formation

Muscle Tissue and Physiology: Structure, Function, and Types

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