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 necessary for crossbridge formation.

Question 2

A patient with Duchenne muscular dystrophy has a mutation affecting dystrophin. What is the primary consequence of this mutation at the cellular level?

Accepted Answer

Disrupted structural linkage between the cytoskeleton and extracellular matrix.

Question 3

Which connective tissue layer directly surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 4

During the sliding filament mechanism, what happens to the length of the A band and I band as the muscle contracts?

Accepted Answer

A band remains the same, I band shortens.

Question 5

Which of the following is TRUE regarding the role of Ca$^{2+}$ in excitation-contraction coupling?

Accepted Answer

Ca$^{2+}$ binds to troponin, causing a conformational change that moves tropomyosin away from myosin binding sites.

Question 6

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

Accepted Answer

It contains multiple nuclei within a single plasma membrane.

Question 7

Which of the following is the correct sequence of events in the crossbridge cycle?

Accepted Answer

Myosin binds ATP, detaches from actin, hydrolyzes ATP, reattaches to actin, performs power stroke.

Question 8

Which protein is responsible for the elastic recoil of muscle after being stretched?

Accepted Answer

Titin

Question 9

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

Accepted Answer

Maintaining posture

Question 10

Which of the following best distinguishes cardiac muscle from skeletal muscle?

Accepted Answer

Cardiac muscle is striated and involuntary, with a pacemaker setting contraction rate.

Question 11

Which of the following statements about myofibrils is CORRECT?

Accepted Answer

Myofibrils contain parallel arrangements of myofilaments forming sarcomeres.

Question 12

Which of the following is a function of myoglobin in skeletal muscle cells?

Accepted Answer

Binding oxygen for use in aerobic metabolism.

Question 13

Which of the following best describes the difference between G-actin and F-actin?

Accepted Answer

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

Question 14

Which of the following events directly leads to muscle relaxation?

Accepted Answer

Reuptake of Ca$^{2+}$ into the sarcoplasmic reticulum.

Question 15

Which of the following is the correct formula for the percentage of myosin heads actively pulling at one time during muscle contraction?

Accepted Answer

$\sim 50\%$

Question 16

Which structure is the contractile unit of muscle?

Accepted Answer

Sarcomere

Question 17

A patient presents with muscle weakness and inability to generate rapid movements. Which muscle type is most likely affected?

Accepted Answer

Skeletal muscle

Question 18

Which of the following is TRUE regarding the role of ATP in muscle contraction?

Accepted Answer

ATP is required for detachment of myosin heads from actin after the power stroke.

Question 19

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

Accepted Answer

They transmit the action potential deep into the muscle fiber.

Question 20

Which of the following is a functional characteristic of muscle tissue that allows it to resume its resting length after being stretched?

Accepted Answer

Elasticity

Cellular Physiology of Muscle: Structure and Function of Muscle Tissue

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