Q: Which equation correctly represents the change in membrane potential during muscle fiber excitation?

$$\Delta V = V_{final} - V_{initial} = +75\,\text{mV} - (-90\,\text{mV}) = 165\,\text{mV}$$

Question 1

Which connective tissue layer surrounds individual muscle fibers in skeletal muscle?

Accepted Answer

Endomysium

Question 2

A patient is exposed to a pesticide that inhibits acetylcholinesterase. What is the most likely physiological effect?

Accepted Answer

Spastic paralysis due to continuous stimulation by acetylcholine

Question 3

Which of the following best describes the role of troponin in muscle contraction?

Accepted Answer

Troponin binds calcium, causing tropomyosin to move and expose actin's active sites

Question 4

During the contraction phase of a muscle twitch, which event occurs at the molecular level?

Accepted Answer

Myosin heads bind to actin and perform a power stroke

Question 5

Which equation correctly represents the change in membrane potential during muscle fiber excitation?

Accepted Answer

$$\Delta V = V_{final} - V_{initial} = +75\,	ext{mV} - (-90\,	ext{mV}) = 165\,	ext{mV}$$

Question 6

Which of the following is TRUE regarding the difference between fast and slow skeletal muscle fibers?

Accepted Answer

Slow fibers contain more myoglobin and are more resistant to fatigue

Question 7

A patient with Duchenne Muscular Dystrophy is most likely to have a mutation in which protein?

Accepted Answer

Dystrophin

Question 8

Which of the following best explains why rigor mortis occurs after death?

Accepted Answer

Lack of ATP prevents detachment of myosin from actin

Question 9

Which structure in the muscle fiber stores calcium ions necessary for contraction?

Accepted Answer

Terminal cisternae of the sarcoplasmic reticulum

Question 10

A patient presents with drooping eyelids and double vision. Laboratory tests reveal antibodies against acetylcholine receptors. What is the most likely diagnosis?

Accepted Answer

Myasthenia gravis

Question 11

Which of the following is a regulatory protein in skeletal muscle?

Accepted Answer

Tropomyosin

Question 12

Which of the following events occurs during the relaxation phase of muscle contraction?

Accepted Answer

Calcium is actively transported back into the sarcoplasmic reticulum

Question 13

Which of the following best describes the function of the neuromuscular junction?

Accepted Answer

It transmits nerve impulses to muscle fibers via acetylcholine

Question 14

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

Accepted Answer

Action potential travels down T tubules → calcium released from SR → calcium binds to troponin → tropomyosin moves off actin

Question 15

Which of the following muscle types is autorhythmic and highly resistant to fatigue due to large mitochondria?

Accepted Answer

Cardiac muscle

Question 16

Which of the following is TRUE regarding the sliding filament theory?

Accepted Answer

Thick and thin filaments slide past each other, causing sarcomere shortening

Question 17

Which of the following best explains why ATP is required for both muscle contraction and relaxation?

Accepted Answer

ATP is required to hydrolyze myosin heads for contraction and to pump calcium back into the SR for relaxation

Question 18

Which of the following is a characteristic of smooth muscle cells?

Accepted Answer

Fusiform shape with a single nucleus and lack of striations

Question 19

A muscle is stimulated at a frequency of 45 stimuli per second, resulting in a sustained contraction with no relaxation. What is this phenomenon called?

Accepted Answer

Complete tetanus

Question 20

Which of the following best describes the function of satellite cells in skeletal muscle?

Accepted Answer

They repair damaged muscle tissue by generating new myofibers

Chapter 11: Muscle Tissue – Structure, Function, and Physiology

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