Question 1

Which of the following best describes the role of the Na$$^+/K$^+$$ ATPase pump in maintaining the resting membrane potential of a muscle cell?

Accepted Answer

It uses ATP to move 3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell, maintaining a negative charge inside.

Question 2

A patient is given a drug that blocks acetylcholine (ACh) receptors on the sarcolemma. What is the most likely effect on muscle contraction?

Accepted Answer

Muscle contraction will be inhibited because ACh cannot bind and open ligand-gated Na$$^+$$ channels.

Question 3

During the excitation phase of muscle contraction, which event directly triggers the release of acetylcholine from the motor neuron?

Accepted Answer

Binding of Ca$$^{2+} to $$synaptic vesicles after Ca$$^{2+}$$ enters the neuron.

Question 4

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

Accepted Answer

ATP is no longer produced, so myosin heads cannot detach from actin.

Question 5

Which equation correctly represents the coupled reaction for ATP production using creatine phosphate in muscle cells?

Accepted Answer

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

Question 6

A marathon runner relies primarily on which pathway for ATP production, and what is the main byproduct?

Accepted Answer

Aerobic respiration; carbon dioxide and water

Question 7

If acetylcholinesterase is inhibited at the neuromuscular junction, what is the most likely outcome?

Accepted Answer

Acetylcholine will accumulate, causing prolonged muscle contraction.

Question 8

Which of the following is TRUE regarding the sliding filament model of muscle contraction?

Accepted Answer

Myosin heads attach to actin, pull it toward the M line, and detach when ATP binds.

Question 9

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

Accepted Answer

Troponin binds Ca$$^{2+}$$, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 10

Which of the following muscle energy sources provides the highest yield of ATP per glucose molecule?

Accepted Answer

Aerobic respiration

Question 11

A child with malignant hyperthermia is exposed to an anesthetic that triggers massive Ca$$^{2+}$$ release from the sarcoplasmic reticulum. What is the most immediate physiological consequence?

Accepted Answer

Uncontrolled muscle contraction and excessive heat production.

Question 12

Which of the following is a direct effect of insufficient ATP during muscle contraction?

Accepted Answer

Myosin heads remain attached to actin, preventing relaxation.

Question 13

Which of the following best explains muscle fatigue during prolonged exercise?

Accepted Answer

Depletion of ATP and accumulation of lactic acid impair muscle contraction.

Question 14

Which of the following statements about the sarcomere during contraction is correct?

Accepted Answer

The Z discs move closer together, increasing overlap between actin and myosin.

Question 15

Which muscle fiber type is most likely to contract when oxygen levels are low, such as during sprinting?

Accepted Answer

Fast-twitch (Type IIb) fibers

Question 16

What would happen to muscle contraction if extracellular calcium levels were abnormally low?

Accepted Answer

Muscle contraction would be impaired because insufficient Ca$$^{2+}$$ would be available to bind troponin.

Question 17

Which of the following is NOT a product of aerobic respiration in muscle cells?

Accepted Answer

Lactic acid

Question 18

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

Accepted Answer

It stores and releases Ca$$^{2+} to $$trigger contraction.

Question 19

Which of the following events occurs FIRST during the excitation-contraction coupling in skeletal muscle?

Accepted Answer

Binding of acetylcholine to ligand-gated channels on the sarcolemma

Question 20

Which of the following is a consequence of not using oxygen to create ATP in muscle cells?

Accepted Answer

Increased production of lactic acid, leading to muscle fatigue

Muscle Physiology: How Muscle Cells Contract

Guida di studio - Domande di pratica

Study guide - Flashcard