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 Ca$^{2+}$ ions, which are essential for triggering muscle contraction.

Question 2

During the sliding filament mechanism, what happens to the length of the sarcomere and the filaments within it?

Accepted Answer

The sarcomere shortens, but the thick and thin filaments remain the same length.

Question 3

Which connective tissue layer surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

A patient with Duchenne muscular dystrophy (DMD) has a mutation affecting which protein, and what is its primary function?

Accepted Answer

Dystrophin; it links the cytoskeleton of muscle fibers to the extracellular matrix.

Question 5

Which of the following is TRUE regarding the functional characteristics of muscle tissue?

Accepted Answer

Extensibility refers to the ability of muscle to be stretched or extended.

Question 6

Which statement best explains the role of ATP in the crossbridge cycle of muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to detach from actin after the power stroke.

Question 7

Which of the following correctly matches the muscle type with its description?

Accepted Answer

Cardiac muscle: striated, involuntary, pacemaker sets rate of contraction.

Question 8

What is the primary function of myoglobin in skeletal muscle fibers?

Accepted Answer

It stores oxygen for use during muscle contraction.

Question 9

Which of the following events occurs FIRST during excitation-contraction coupling in skeletal muscle?

Accepted Answer

An action potential travels along the sarcolemma and down the T-tubules.

Question 10

A muscle fiber is described as a syncytium. What does this mean?

Accepted Answer

It is a multinucleated cell formed by the fusion of precursor cells.

Question 11

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

Accepted Answer

It blocks myosin binding sites on actin when Ca$^{2+}$ is absent.

Question 12

If extracellular Ca$^{2+}$ concentration is low, what is the effect on muscle contraction?

Accepted Answer

Myosin binding sites on actin remain blocked, preventing contraction.

Question 13

Which structure is the contractile unit of muscle?

Accepted Answer

Sarcomere

Question 14

What is the main difference between G-actin and F-actin?

Accepted Answer

G-actin is a globular monomer, while F-actin is a filamentous polymer formed by G-actin subunits.

Question 15

Which of the following is a function of skeletal muscle?

Accepted Answer

Generating heat to maintain body temperature.

Question 16

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

Accepted Answer

It provides elasticity and helps the muscle fiber recoil after being stretched.

Question 17

A patient is unable to maintain posture and frequently falls. Which muscle function is most likely impaired?

Accepted Answer

Maintaining posture by constantly working against gravity.

Question 18

Which of the following is TRUE regarding the arrangement of myofilaments in a sarcomere?

Accepted Answer

Thick filaments are composed of myosin and are located in the A band.

Question 19

Which of the following best explains how muscle relaxation occurs after contraction?

Accepted Answer

The sarcoplasmic reticulum reclaims Ca$^{2+}$, causing tropomyosin to block myosin binding sites on actin.

Question 20

A multi-step scenario: A person is exposed to a neurotoxin that blocks acetylcholine release at the neuromuscular junction. What is the most immediate effect on muscle contraction, and which cellular structure is directly affected?

Accepted Answer

No action potential is generated on the sarcolemma, preventing Ca$^{2+}$ release from the sarcoplasmic reticulum.

Cellular Physiology of Muscle: Structure and Function of Muscle Cells

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