$$\text{ATP} \rightarrow \text{ADP} + \text{P}_i$$

Question 1

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

Accepted Answer

Troponin binds to calcium ions, causing a conformational change that moves tropomyosin away from actin's myosin-binding sites.

Question 2

During muscle contraction, which event directly follows the release of ADP and Pi from the myosin head?

Accepted Answer

The myosin head pivots and pulls the actin filament toward the M line (power stroke).

Question 3

Which equation best represents the hydrolysis of ATP during the cocking of the myosin head?

Accepted Answer

$$	ext{ATP} ightarrow 	ext{ADP} + 	ext{P}_i$$

Question 4

Which of the following is TRUE regarding the neuromuscular junction?

Accepted Answer

It contains synaptic vesicles filled with acetylcholine (ACh) in the axon terminal.

Question 5

What is the primary function of acetylcholine (ACh) at the neuromuscular junction?

Accepted Answer

ACh binds to chemically gated ion channels on the sarcolemma, initiating an action potential.

Question 6

Which of the following best describes the sequence of events in skeletal muscle contraction?

Accepted Answer

Events at neuromuscular junction, muscle fiber excitation, excitation-contraction coupling, cross bridge cycling

Question 7

Which statement correctly compares slow oxidative (Type I) and fast glycolytic (Type IIb/IIx) muscle fibers?

Accepted Answer

Type IIb/IIx fibers have fewer mitochondria and fatigue more rapidly than Type I fibers.

Question 8

Which of the following is a characteristic of the resting membrane potential in skeletal muscle fibers?

Accepted Answer

The inside of the cell is negative relative to the outside, typically around $$-70\ 	ext{mV}.$$

Question 9

Which event marks the beginning of muscle fiber relaxation?

Accepted Answer

Detachment of myosin from actin after ATP binds to the myosin head.

Question 10

A patient presents with muscle rigidity after death (rigor mortis). Which of the following best explains this phenomenon?

Accepted Answer

ATP is depleted, preventing myosin heads from detaching from actin, resulting in sustained contraction.

Question 11

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

Accepted Answer

The SR stores and releases calcium ions ($$	ext{Ca}^{2+}) in $$response to an action potential.

Question 12

Which of the following is TRUE regarding excitation-contraction coupling?

Accepted Answer

It involves the propagation of an action potential along the sarcolemma and the release of $$	ext{Ca}^{2+}$$ from the SR.

Question 13

Which of the following is a direct result of calcium ion ($$	ext{Ca}^{2+}) $$release from the sarcoplasmic reticulum during muscle contraction?

Accepted Answer

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

Question 14

Which of the following best describes the function of voltage-gated ion channels in skeletal muscle contraction?

Accepted Answer

They open in response to changes in membrane potential, propagating the action potential along the sarcolemma.

Question 15

Which of the following is TRUE regarding the cross bridge cycle?

Accepted Answer

ATP binding to myosin causes the myosin head to detach from actin.

Question 16

Which of the following muscle fiber types is best suited for endurance activities such as marathon running?

Accepted Answer

Slow oxidative (Type I)

Question 17

Which of the following best describes the anatomical relationship between T tubules and the sarcoplasmic reticulum (SR) in skeletal muscle fibers?

Accepted Answer

T tubules are invaginations of the sarcolemma that transmit action potentials deep into the muscle fiber, adjacent to the SR.

Question 18

Which of the following best explains why fast glycolytic fibers fatigue more quickly than slow oxidative fibers?

Accepted Answer

Fast glycolytic fibers rely primarily on anaerobic glycolysis, which produces lactic acid and less ATP per glucose molecule.

Question 19

Which of the following is the correct sequence for the cross bridge cycle in skeletal muscle contraction?

Accepted Answer

Cross bridge formation, power stroke, cross bridge detachment, cocking of myosin head

Skeletal Muscle Contraction: Structure, Physiology, and Mechanisms

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