Question 1

Which of the following best describes the role of acetylcholinesterase (AChE) at the neuromuscular junction?

Accepted Answer

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

Question 2

What is the immediate effect of acetylcholine binding to receptors on the motor end plate?

Accepted Answer

Increased permeability to sodium ions, leading to depolarization.

Question 3

During muscle contraction, which event directly follows the release of calcium ions from the sarcoplasmic reticulum?

Accepted Answer

Troponin binds calcium, causing tropomyosin to move and expose active sites.

Question 4

Which equation best represents the breakdown of acetylcholine by acetylcholinesterase?

Accepted Answer

$$\mathrm{ACh} + \mathrm{H}_2\mathrm{O} \xrightarrow{\mathrm{AChE}} \mathrm{Acetate} + \mathrm{Choline}$$

Question 5

A patient is exposed to a toxin that blocks voltage-gated calcium channels at the synaptic terminal of a motor neuron. What is the most likely effect on muscle contraction?

Accepted Answer

Acetylcholine release is inhibited, preventing muscle contraction.

Question 6

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

Accepted Answer

ATP is depleted, preventing detachment of myosin heads from actin.

Question 7

Which of the following is true regarding the relationship between load and speed of muscle contraction?

Accepted Answer

As load increases, contraction speed decreases.

Question 8

A muscle fiber is stimulated repeatedly before it has completely relaxed. What phenomenon is most likely to occur?

Accepted Answer

Wave summation, resulting in increased tension.

Question 9

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 skeletal muscle fiber.

Question 10

If acetylcholinesterase is inhibited by a drug, what is the most likely effect on muscle activity?

Accepted Answer

Prolonged muscle contraction due to continued presence of acetylcholine.

Question 11

Which of the following is NOT a factor that determines the duration of muscle contraction?

Accepted Answer

Number of mitochondria in the presynaptic neuron.

Question 12

Which process is responsible for the release of acetylcholine from the synaptic vesicles into the synaptic cleft?

Accepted Answer

Exocytosis

Question 13

What is the primary function of troponin during muscle contraction?

Accepted Answer

It binds calcium ions, causing tropomyosin to move and expose actin's active sites.

Question 14

Which of the following best describes a concentric muscle contraction?

Accepted Answer

Muscle tension exceeds the load and the muscle shortens.

Question 15

A patient with tetanus infection experiences sustained muscle contractions. What is the underlying cause?

Accepted Answer

A neurotoxin prevents inhibitory signals, causing continuous stimulation of muscles.

Question 16

Which of the following best explains the concept of motor unit recruitment?

Accepted Answer

Gradually increasing the number of motor units activated to produce greater tension.

Question 17

Which phase of a muscle twitch is characterized by the release of calcium ions and the beginning of cross-bridge formation?

Accepted Answer

Contraction phase

Question 18

Which of the following is true about isometric muscle contractions?

Accepted Answer

Muscle tension is produced, but the muscle does not change length.

Question 19

Which of the following best describes the role of elastic forces in muscle relaxation?

Accepted Answer

They help return the muscle to its resting length after contraction.

Question 20

Which of the following is a direct result of acetylcholine binding to its receptor on the muscle fiber?

Accepted Answer

Opening of ligand-gated sodium channels in the sarcolemma.

Muscle Tissue: Structure, Function, and Control of Skeletal Muscle Activity

Guida di studio - Domande di pratica

Study guide - Flashcard