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

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

Question 1

Which of the following best describes the role of calcium ions ($$\mathrm{Ca$$^{2+}$$}) in $$skeletal muscle contraction?

Accepted Answer

They bind to troponin, causing tropomyosin to move and expose actin binding sites.

Question 2

During excitation-contraction coupling, which sequence of events occurs immediately after acetylcholine binds to its receptor on the motor end plate?

Accepted Answer

Action potential is generated along the sarcolemma.

Question 3

Which structure stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) $$during muscle contraction?

Accepted Answer

Sarcoplasmic reticulum

Question 4

A patient is exposed to a toxin that inhibits acetylcholinesterase at the neuromuscular junction. What is the most likely physiological effect?

Accepted Answer

Prolonged muscle contraction due to continuous stimulation.

Question 5

Which of the following best distinguishes isotonic from isometric muscle contractions?

Accepted Answer

Isotonic contractions involve muscle length change while tension remains constant.

Question 6

Which protein directly blocks the myosin binding sites on actin in a resting muscle?

Accepted Answer

Tropomyosin

Question 7

A muscle fiber is stimulated at increasing frequencies. Which phenomenon occurs when stimuli are so frequent that no relaxation occurs between contractions?

Accepted Answer

Complete tetanus

Question 8

Which of the following is true regarding motor units and the force of contraction?

Accepted Answer

Recruitment of additional motor units increases the force of contraction.

Question 9

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 10

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

Accepted Answer

Lack of ATP prevents detachment of myosin from actin.

Question 11

Which muscle fiber type is most resistant to fatigue and why?

Accepted Answer

Slow oxidative fibers, because they have abundant mitochondria and myoglobin.

Question 12

A marathon runner relies primarily on which energy pathway during prolonged exercise?

Accepted Answer

Aerobic respiration

Question 13

Which of the following is a property shared by all muscle tissue types?

Accepted Answer

Ability to contract in response to electrical stimulation

Question 14

Which event occurs at the neuromuscular junction to initiate muscle contraction?

Accepted Answer

Acetylcholine is released from the motor neuron and binds to receptors on the muscle fiber.

Question 15

Which of the following best describes muscle tone?

Accepted Answer

Sustained partial contraction of muscles, even at rest.

Question 16

A patient with myasthenia gravis has reduced acetylcholine receptor function. What is the expected effect on muscle contraction?

Accepted Answer

Decreased muscle contraction due to impaired synaptic transmission.

Question 17

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

Accepted Answer

Action potential travels along sarcolemma → $$\mathrm{Ca$$^{2+}$$}$$ released from sarcoplasmic reticulum → Troponin binds $$\mathrm{Ca$$^{2+}$$}$$ → Tropomyosin moves → Myosin binds actin

Question 18

Which of the following best explains the difference between slow-twitch (Type I) and fast-twitch (Type II) muscle fibers?

Accepted Answer

Slow-twitch fibers are adapted for endurance and aerobic metabolism.

Question 19

Which of the following is a direct result of wave summation in skeletal muscle?

Accepted Answer

Greater force of contraction due to increased stimulus frequency.

Muscle Physiology: Structure, Function, and Contraction Mechanisms

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