Question 1

Which of the following best describes the main structural difference between skeletal, cardiac, and smooth muscle cells?

Accepted Answer

Skeletal muscle cells are multinucleated and striated, cardiac muscle cells are branching and striated with intercalated discs, and smooth muscle cells are spindle-shaped and non-striated.

Question 2

Which connective tissue layer directly surrounds individual muscle fibers?

Accepted Answer

Endomysium

Question 3

During the sliding filament model of muscle contraction, which event occurs first?

Accepted Answer

Calcium ions bind to troponin, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 4

Which process is responsible for the rapid regeneration of ATP during the first few seconds of intense muscle activity?

Accepted Answer

Direct phosphorylation by creatine phosphate

Question 5

A patient is unable to perform fine motor tasks with their fingers. Which of the following best explains this deficit?

Accepted Answer

Their finger muscles have large motor units, resulting in less precise control.

Question 6

Which of the following is a function of the sarcoplasmic reticulum in skeletal muscle fibers?

Accepted Answer

Storing and releasing calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$for muscle contraction

Question 7

Which of the following best describes the role of acetylcholinesterase at the neuromuscular junction?

Accepted Answer

It breaks down acetylcholine, terminating the signal for muscle contraction.

Question 8

Which of the following muscle fiber types would be most prevalent in the quadriceps of a marathon runner?

Accepted Answer

Slow oxidative fibers (Type I)

Question 9

Which of the following best explains why cardiac muscle can contract without nervous system stimulation?

Accepted Answer

Cardiac muscle cells have intrinsic pacemaker activity.

Question 10

A muscle is contracting but not shortening, as when pushing against an immovable object. What type of contraction is this?

Accepted Answer

Isometric contraction

Question 11

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

Accepted Answer

Action potential travels along sarcolemma → Ca$$^{2+}$$ released from SR → Ca$$^{2+}$$ binds to troponin → Cross-bridge formation

Question 12

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

Accepted Answer

Smooth muscle contraction is regulated by calmodulin and myosin light chain kinase (MLCK).

Question 13

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

Accepted Answer

Accumulation of lactic acid and depletion of ATP

Question 14

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 15

Which of the following best describes the effect of aerobic exercise on skeletal muscle?

Accepted Answer

Increases capillary density and mitochondrial number in muscle fibers

Question 16

Which of the following is a characteristic of unitary (visceral) smooth muscle?

Accepted Answer

Cells are electrically coupled by gap junctions and contract as a unit.

Question 17

Which of the following best explains why the force of skeletal muscle contraction increases with muscle size?

Accepted Answer

Larger muscles contain more myofibrils, allowing for greater cross-bridge formation.

Question 18

Which of the following is the primary source of calcium ions for contraction in smooth muscle?

Accepted Answer

Extracellular fluid and sarcoplasmic reticulum

Question 19

Which of the following best describes the function of myoglobin in skeletal muscle fibers?

Accepted Answer

Stores oxygen for use during muscle activity

Question 20

Which of the following is a correct statement about the cross-bridge cycle during muscle contraction?

Accepted Answer

ATP hydrolysis re-cocks the myosin head for another cycle.

Muscles and Muscle Tissue: Structure, Function, and Contraction Mechanisms

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