Question 1

Which of the following best describes the difference between isotonic and isometric muscle contractions?

Accepted Answer

Isotonic contractions involve muscle length change with constant tension, while isometric contractions generate force without changing muscle length.

Question 2

During the depolarization phase of an action potential in a neuron, which ion channels open and what is the direction of ion movement?

Accepted Answer

Sodium channels open, and Na$$^+$$ moves into the cell.

Question 3

A patient is experiencing muscle weakness due to a defect in the acetylcholine receptor at the neuromuscular junction. Which process is most directly impaired?

Accepted Answer

Generation of an end plate potential in the muscle fiber

Question 4

Which of the following best explains why the resting membrane potential of a neuron is negative?

Accepted Answer

There is greater permeability to K$$^+$$ than Na$$^+ at $$rest, and K$$^+$$ diffuses out of the cell.

Question 5

Which of the following is the correct sequence of events for muscle contraction at the molecular level?

Accepted Answer

Calcium binds to troponin, tropomyosin shifts, myosin binds to actin, power stroke occurs.

Question 6

A muscle fiber is stimulated at a high frequency, resulting in a sustained contraction without relaxation. What is this phenomenon called?

Accepted Answer

Tetanus

Question 7

Which of the following best describes the 'all-or-none' principle of action potentials?

Accepted Answer

Once threshold is reached, an action potential of fixed size is generated; subthreshold stimuli do not produce action potentials.

Question 8

During muscle relaxation, which process is essential for returning calcium ions to the sarcoplasmic reticulum?

Accepted Answer

Active transport of Ca$$^{2+} by $$the Ca$$^{2+}-$$ATPase pump

Question 9

A person is running a marathon and experiences muscle fatigue. Which of the following is a major contributor to this fatigue?

Accepted Answer

Accumulation of inorganic phosphate and lactic acid in muscle cells

Question 10

Which of the following best explains why cardiac muscle cannot undergo tetanus?

Accepted Answer

The refractory period in cardiac muscle is longer than the contraction period, preventing summation.

Question 11

Which of the following statements about the sodium-potassium pump is correct?

Accepted Answer

It moves 3 Na$$^+$$ out of the cell and 2 K$$^+$$ into the cell per ATP hydrolyzed.

Question 12

A patient is given a drug that blocks voltage-gated calcium channels at the axon terminal of a motor neuron. What is the most immediate effect?

Accepted Answer

Inhibition of acetylcholine release into the synaptic cleft

Question 13

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

Accepted Answer

Troponin binds calcium, causing tropomyosin to move and expose myosin-binding sites on actin.

Question 14

Which of the following is true regarding the refractory period of a neuron?

Accepted Answer

It is the period during which a neuron cannot generate another action potential, regardless of stimulus strength.

Question 15

Which of the following best explains the role of ATP in the cross-bridge cycle of muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to detach from actin after the power stroke.

Question 16

A person is exposed to a toxin that prevents the breakdown of acetylcholine in the synaptic cleft. What is the most likely effect on muscle function?

Accepted Answer

Sustained muscle contraction (spastic paralysis) due to continuous stimulation

Question 17

Which of the following best describes the function of the T-tubules in skeletal muscle fibers?

Accepted Answer

They conduct action potentials from the sarcolemma into the interior of the muscle fiber.

Question 18

Which of the following is a key difference between fast-twitch and slow-twitch muscle fibers?

Accepted Answer

Slow-twitch fibers rely more on aerobic metabolism and are more resistant to fatigue than fast-twitch fibers.

Question 19

Which of the following best explains the effect of hyperkalemia (elevated extracellular K$$^+) on $$the resting membrane potential of a neuron?

Accepted Answer

It depolarizes the membrane, making it more likely to fire an action potential.

Comprehensive Study Guide: Muscle Physiology, Neurophysiology, and Synaptic Transmission

Guida di studio - Domande di pratica

Study guide - Flashcard