Q: A patient is unable to maintain muscle contraction despite continued stimulation. Which of the following is the most likely physiological cause of this muscle fatigue?

Disruption of membrane potential due to imbalances in K\textsuperscript{+}, Na\textsuperscript{+}, and Ca\textsuperscript{2+} ions.

Question 1

Which of the following best describes the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions involve muscle length change and movement of a load, while isometric contractions generate tension without changing muscle length.

Question 2

A patient is unable to maintain muscle contraction despite continued stimulation. Which of the following is the most likely physiological cause of this muscle fatigue?

Accepted Answer

Disruption of membrane potential due to imbalances in K	extsuperscript{+}, Na	extsuperscript{+}, and Ca	extsuperscript{2+} ions.

Question 3

Which equation correctly represents the direct phosphorylation of ADP by creatine phosphate in muscle cells?

Accepted Answer

$$\mathrm{ADP} + \mathrm{CP} \rightarrow \mathrm{ATP} + \mathrm{Creatine}$$

Question 4

During a sustained muscle contraction, which process is responsible for the rapid replenishment of ATP after initial stores are depleted?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate.

Question 5

A sprinter is running a 100-meter dash. Which metabolic pathway is primarily supplying ATP to their muscles during the first few seconds of the race?

Accepted Answer

Direct phosphorylation of ADP by creatine phosphate.

Question 6

Which of the following best explains why smooth muscle can maintain contraction for long periods with minimal fatigue?

Accepted Answer

Smooth muscle contraction is slow, sustained, and most ATP is generated aerobically.

Question 7

Which statement about the length-tension relationship in skeletal muscle is correct?

Accepted Answer

Force decreases if sarcomere length is less than 80% or greater than 120% of resting length.

Question 8

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

Accepted Answer

Smooth muscle fibers are spindle-shaped, have a single nucleus, and lack striations.

Question 9

A muscle is stimulated at increasing frequencies, and each contraction builds on the previous one until a smooth, sustained contraction is achieved. What is this phenomenon called?

Accepted Answer

Tetanus (temporal summation).

Question 10

Which of the following best describes the role of calmodulin in smooth muscle contraction?

Accepted Answer

Calmodulin binds calcium ions and activates myosin light chain kinase, initiating contraction.

Question 11

Which of the following is true regarding the energy efficiency of muscle contraction?

Accepted Answer

Only about 40% of the energy released is used for work; the rest is lost as heat.

Question 12

Which of the following best explains the stress-relaxation response in smooth muscle?

Accepted Answer

Smooth muscle briefly contracts in response to stretch, then adapts to the new length and relaxes.

Question 13

Which of the following is a correct statement about motor unit recruitment in skeletal muscle?

Accepted Answer

Increasing stimulus strength recruits more motor units, increasing contractile force.

Question 14

Which of the following is a property of single-unit (visceral) smooth muscle?

Accepted Answer

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

Question 15

Which of the following best describes the role of the Na	extsuperscript{+}/K	extsuperscript{+} pump during muscle contraction?

Accepted Answer

It restores ion gradients after excitation-contraction coupling.

Question 16

Which of the following is true regarding the oxygen debt (EPOC) after intense exercise?

Accepted Answer

EPOC refers to the amount of oxygen needed to restore muscle to its pre-exercise state.

Question 17

Which of the following is a correct statement about the source of calcium for contraction in smooth muscle?

Accepted Answer

Most calcium used for contraction in smooth muscle comes from extracellular sources.

Question 18

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

Accepted Answer

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

Question 19

A muscle fiber is stimulated with a load greater than the tension it can develop. What type of contraction occurs?

Accepted Answer

Isometric contraction.

Contractile Properties of Skeletal and Smooth Muscles: Anatomy & Physiology I Study Notes

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