Question 1

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

Accepted Answer

It is the site where a motor neuron communicates with a muscle fiber to initiate muscle contraction.

Question 2

During the process of muscle contraction, which event directly follows the release of acetylcholine (ACh) into the synaptic cleft?

Accepted Answer

ACh binds to receptors on the muscle fiber's sarcolemma, causing ion channels to open.

Question 3

A patient is exposed to a toxin that blocks voltage-gated Na$$^+$$ channels on the sarcolemma. Which of the following would most likely occur?

Accepted Answer

The muscle fiber would not be able to generate an action potential, preventing contraction.

Question 4

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

Accepted Answer

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

Question 5

Which of the following events occurs during the repolarization phase of the muscle action potential?

Accepted Answer

Voltage-gated K$$^+$$ channels open, allowing K$$^+ to $$exit the cell.

Question 6

A muscle fiber is unable to relax after contraction. Which of the following is the most likely cause?

Accepted Answer

Calcium ions are not being pumped back into the sarcoplasmic reticulum.

Question 7

Which of the following best describes the 'refractory period' in skeletal muscle fibers?

Accepted Answer

It is the time after an action potential during which the muscle fiber cannot be stimulated again until repolarization is complete.

Question 8

Which of the following is the correct sequence of events for muscle fiber contraction (cross-bridge cycling)?

Accepted Answer

1. Myosin heads attach to actin, 2. Power stroke, 3. ATP binds to myosin, 4. Myosin detaches from actin

Question 9

A patient with myasthenia gravis experiences muscle weakness due to:

Accepted Answer

Autoimmune destruction of acetylcholine receptors at the neuromuscular junction.

Question 10

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, resulting in sustained contraction.

Question 11

During the depolarization phase of the muscle action potential, which ion movement is primarily responsible for the change in membrane potential?

Accepted Answer

Na$$^+$$ ions enter the muscle fiber through voltage-gated channels.

Question 12

Which of the following best describes the 'motor unit' in skeletal muscle?

Accepted Answer

A single motor neuron and all the muscle fibers it innervates.

Question 13

Which of the following is true regarding the 'all-or-none' principle of muscle fiber contraction?

Accepted Answer

A muscle fiber contracts completely or not at all in response to a threshold stimulus.

Question 14

Which of the following best explains why larger, fleshy muscles contract more slowly and hold contraction longer than smaller muscles?

Accepted Answer

They have slower myosin ATPase activity and different enzyme properties.

Question 15

Which of the following events occurs during the latent period of a muscle twitch?

Accepted Answer

Excitation-contraction coupling occurs, but no tension is produced yet.

Question 16

A researcher measures the membrane potential of a muscle fiber and finds it is returning to its resting value after an action potential. Which process is most responsible for this change?

Accepted Answer

Efflux of K$$^+$$ ions through voltage-gated channels.

Question 17

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

Accepted Answer

It breaks down acetylcholine in the synaptic cleft, terminating the signal.

Question 18

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

Accepted Answer

1. Action potential travels down T-tubules, 2. Ca$$^{2+}$$ released from SR, 3. Ca$$^{2+}$$ binds to troponin, 4. Cross-bridge formation

Question 19

A muscle fiber is repeatedly stimulated at a high frequency, and the tension does not return to baseline between stimuli. Which phenomenon is being observed?

Accepted Answer

Tetanus

Muscle Contraction and Neuromuscular Physiology Study Notes

Guida di studio - Domande di pratica

Study guide - Flashcard