$$\mathrm{ATP} + \mathrm{H_2O} \rightarrow \mathrm{ADP} + \mathrm{P_i} + \text{energy}$$

Question 1

Which of the following statements best describes the role of the sarcoplasmic reticulum in skeletal muscle contraction?

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$necessary for muscle contraction.

Question 2

During the crossbridge cycle, what event directly causes the power stroke that moves actin filaments?

Accepted Answer

Release of inorganic phosphate ($$\mathrm{P_i}) $$from the myosin head.

Question 3

Which protein blocks the myosin-binding sites on actin in a relaxed muscle fiber?

Accepted Answer

Tropomyosin

Question 4

A patient is unable to relax their muscles after contraction. Which process is most likely impaired?

Accepted Answer

Active transport of $$\mathrm{Ca$$^{2+}$$}$$ back into the sarcoplasmic reticulum by Ca$$^{2+}-$$ATPase.

Question 5

Which equation correctly represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$$\mathrm{ATP} + \mathrm{H_2O} ightarrow \mathrm{ADP} + \mathrm{P_i} + 	ext{energy}$$

Question 6

Which of the following best explains the function of titin in the sarcomere?

Accepted Answer

It stabilizes the position of thick filaments and returns muscle to resting length after stretch.

Question 7

What is the primary neurotransmitter released at the neuromuscular junction to initiate muscle contraction?

Accepted Answer

Acetylcholine

Question 8

Which of the following correctly matches the muscle type with its characteristic?

Accepted Answer

Cardiac muscle: striated and involuntary

Question 9

If a muscle fiber is unable to generate force, which structure is most likely dysfunctional?

Accepted Answer

Myofibrils

Question 10

Which process occurs immediately after acetylcholine binds to receptors on the muscle cell membrane?

Accepted Answer

Opening of sodium channels and generation of an action potential.

Question 11

Which of the following best describes the sliding filament theory of muscle contraction?

Accepted Answer

Actin and myosin filaments slide past each other, shortening the sarcomere.

Question 12

Which structure transmits the action potential deep into the muscle fiber to trigger contraction?

Accepted Answer

T-tubules

Question 13

A muscle is described as antagonistic to another. What does this mean?

Accepted Answer

It produces the opposite movement at a joint compared to the other muscle.

Question 14

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

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release → Troponin activation → Crossbridge formation

Question 15

Which muscle structure is directly responsible for the striated appearance of skeletal muscle?

Accepted Answer

The arrangement of sarcomeres within myofibrils.

Question 16

Which of the following is a function of nebulin in the sarcomere?

Accepted Answer

It helps align actin filaments within the sarcomere.

Question 17

Which event marks the end of the contraction cycle and the beginning of muscle relaxation?

Accepted Answer

Detachment of myosin from actin after ATP binds to myosin.

Question 18

A mutation prevents troponin from binding calcium. What is the most likely consequence?

Accepted Answer

Muscle contraction cannot be initiated because tropomyosin remains in place.

Question 19

Which of the following best describes the role of ATP in the crossbridge cycle?

Accepted Answer

ATP binding to myosin causes myosin to detach from actin.

Question 20

Which of the following is a direct result of calcium binding to troponin during muscle contraction?

Accepted Answer

Tropomyosin moves away from myosin-binding sites on actin.

Chapter 12: Muscles – Structure and Function in Human Physiology

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