Question 1

Which of the following best describes the sequence of events that must occur for skeletal muscle contraction?

Accepted Answer

Neuromuscular junction events, muscle fiber excitation, excitation-contraction coupling, cross-bridge cycling

Question 2

During the events at the neuromuscular junction, what is the primary role of voltage-gated calcium channels?

Accepted Answer

To trigger the release of acetylcholine from the motor neuron

Question 3

Which of the following equations correctly represents the direct phosphorylation of ADP by creatine phosphate (CP) in muscle cells?

Accepted Answer

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

Question 4

A patient is exposed to a drug that inhibits acetylcholinesterase. What is the most likely effect on muscle contraction?

Accepted Answer

Muscle contraction will be prolonged due to continued presence of acetylcholine.

Question 5

Which phase of a muscle twitch corresponds to the time when calcium is being re-sequestered into the sarcoplasmic reticulum?

Accepted Answer

Period of relaxation

Question 6

If a muscle is stimulated at a frequency that does not allow complete relaxation between stimuli, what is the resulting phenomenon called?

Accepted Answer

Unfused (incomplete) tetanus

Question 7

Which of the following best explains why eye muscles contract more rapidly than calf muscles?

Accepted Answer

Eye muscles have different metabolic properties and enzymes compared to calf muscles.

Question 8

A muscle is contracting but not shortening, and the load is greater than the tension the muscle can develop. What type of contraction is this?

Accepted Answer

Isometric contraction

Question 9

Which of the following is true regarding the cross-bridge cycle in skeletal muscle contraction?

Accepted Answer

Hydrolysis of ATP cocks the myosin head into a high-energy state.

Question 10

Which of the following statements about smooth muscle contraction is correct?

Accepted Answer

Smooth muscle contraction requires phosphorylation of myosin by myosin light chain kinase.

Question 11

A muscle fiber is stimulated by a series of action potentials at increasing frequency. Which of the following best describes the resulting increase in muscle tension?

Accepted Answer

Wave (temporal) summation

Question 12

Which of the following best explains the 'size principle' in motor unit recruitment?

Accepted Answer

Smaller motor units are recruited first, followed by larger ones as stimulus intensity increases.

Question 13

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

Accepted Answer

Use of calmodulin for calcium binding

Question 14

A marathon runner is able to sustain muscle contraction for hours. Which energy pathway is primarily responsible for this endurance?

Accepted Answer

Aerobic pathway

Question 15

Which of the following best describes the mechanism by which smooth muscle can maintain contraction over a wide range of lengths?

Accepted Answer

Stress-relaxation response

Question 16

Which of the following is NOT a function of ATP in muscle contraction?

Accepted Answer

Opening voltage-gated sodium channels

Question 17

A muscle fiber is exposed to a subthreshold stimulus. What is the expected response?

Accepted Answer

No observable contraction

Question 18

Which of the following best explains why smooth muscle can contract even when stretched to twice its resting length?

Accepted Answer

It has a lattice-like arrangement of intermediate filaments and dense bodies.

Question 19

Which of the following is the correct order of events in the cross-bridge cycle?

Accepted Answer

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

Question 20

Which of the following best describes the effect of increasing the load on a muscle during contraction?

Accepted Answer

The muscle contracts more slowly and for a shorter duration.

Muscle Contraction: Mechanisms and Types in Skeletal and Smooth Muscle

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