Question 1

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

Accepted Answer

Isotonic contractions involve muscle shortening or lengthening with movement of the load, while isometric contractions generate tension without changing muscle length.

Question 2

A patient is unable to maintain a 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+, Na+, and Ca2+ ions.

Question 3

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 primarily uses aerobic pathways for ATP generation.

Question 4

During a high-intensity sprint, a runner's muscles switch from aerobic to anaerobic metabolism. What is the term for the point at which this switch occurs?

Accepted Answer

Anaerobic threshold

Question 5

Which of the following mechanisms is responsible for the graded strength of skeletal muscle contractions?

Accepted Answer

Changing the frequency and strength of stimulation, which alters the number of motor units activated.

Question 6

A muscle fiber is stimulated repeatedly at a high frequency, resulting in a smooth, sustained contraction. What is this phenomenon called?

Accepted Answer

Tetanus

Question 7

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

Accepted Answer

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

Question 8

Which of the following statements about the length-tension relationship in skeletal muscle is correct?

Accepted Answer

Force decreases if sarcomere length is greater than 120% of resting length due to insufficient filament overlap.

Question 9

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

Accepted Answer

Smooth muscle contraction is regulated by calmodulin binding to Ca2+ instead of troponin.

Question 10

A patient with a genetic mutation affecting myosin ATPase activity in skeletal muscle would most likely experience which of the following?

Accepted Answer

Slower muscle contraction due to reduced ATP hydrolysis rate.

Question 11

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

Accepted Answer

It restores ion gradients after excitation-contraction coupling.

Question 12

Which of the following is true regarding the energy systems used during light-to-moderate exercise?

Accepted Answer

Aerobic respiration provides ATP, allowing activity to continue for hours.

Question 13

Which of the following is a consequence of post-exercise oxygen consumption (EPOC)?

Accepted Answer

Lactic acid is reconverted to pyruvic acid.

Question 14

Which of the following best explains why all muscle fibers in a single motor unit are the same type?

Accepted Answer

Each motor neuron only innervates fibers with identical metabolic and contractile properties.

Question 15

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

Accepted Answer

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

Question 16

Which of the following best describes 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 17

Which of the following is true regarding the source of calcium for smooth muscle contraction?

Accepted Answer

Most calcium comes from extracellular sources.

Question 18

Which of the following is a correct statement about the ratio of thick to thin filaments in smooth versus skeletal muscle?

Accepted Answer

Smooth muscle has a thick to thin filament ratio of 1:13, allowing for more actin-gripping heads.

Question 19

Which of the following best explains why smooth muscle can contract between half and twice its resting length?

Accepted Answer

Smooth muscle filaments spiral down the cell, allowing for greater length changes.

2E) Contractile Properties of Skeletal and Smooth Muscles: Anatomy & Physiology I Study Notes

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