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

Question 1

Which of the following best describes the Sliding Filament Theory of muscle contraction?

Accepted Answer

It explains how muscle fibers shorten by the sliding of actin and myosin filaments past each other.

Question 2

What is the role of ATP in the cross-bridge cycle during muscle contraction?

Accepted Answer

ATP binds to myosin, causing it to detach from actin and reset for another contraction.

Question 3

Which structure is responsible for transmitting the action potential from the neuron to the muscle fiber?

Accepted Answer

The neuromuscular junction

Question 4

During muscle contraction, which ion is released from the sarcoplasmic reticulum to initiate the process?

Accepted Answer

Calcium ($$Ca^{2+})$$

Question 5

What is the function of troponin and tropomyosin in muscle contraction?

Accepted Answer

They regulate the exposure of actin binding sites to myosin by responding to calcium ions.

Question 6

Which of the following correctly lists the sequence of events in muscle contraction?

Accepted Answer

Action potential → Calcium release → Troponin activation → Cross-bridge formation

Question 7

If a toxin blocks acetylcholine release at the neuromuscular junction, what is the most likely effect?

Accepted Answer

Muscle contraction will not occur because the action potential cannot be transmitted to the muscle fiber.

Question 8

Which equation best represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$$ATP ightarrow ADP + P_i + 	ext{energy}$$

Question 9

A patient with a genetic defect in the sarcolemma would most likely experience which symptom?

Accepted Answer

Impaired transmission of action potentials, leading to muscle weakness.

Question 10

Which of the following is TRUE regarding the role of mitochondria in muscle contraction?

Accepted Answer

Mitochondria produce ATP, which is required for both contraction and relaxation of muscle fibers.

Question 11

Which process directly causes the myosin head to detach from actin during the cross-bridge cycle?

Accepted Answer

Binding of ATP to the myosin head

Question 12

If the sarcoplasmic reticulum fails to reabsorb calcium ions after contraction, what is the likely outcome?

Accepted Answer

Muscle remains contracted and cannot relax (rigor)

Question 13

Which of the following best describes the function of the sarcomere?

Accepted Answer

It is the contractile unit of a muscle fiber, containing actin and myosin filaments.

Question 14

Which event occurs immediately after acetylcholine binds to receptors on the sarcolemma?

Accepted Answer

An action potential is generated in the muscle fiber.

Question 15

A patient is unable to produce enough ATP in their muscle cells. Which step in the sliding filament theory would be most directly affected?

Accepted Answer

Detachment of myosin from actin, leading to impaired muscle relaxation.

Question 16

Which of the following is a direct result of calcium binding to troponin during muscle contraction?

Accepted Answer

Tropomyosin moves away from actin binding sites, allowing myosin to bind.

Question 17

Which formula represents the relationship between force generated by a muscle and the number of cross-bridges formed?

Accepted Answer

$$F \propto N_{cb}$$, where $$F is $$force and $$N_{cb} is $$the number of cross-bridges.

Question 18

Which of the following best explains why muscle contraction is considered an 'all-or-none' response at the level of a single muscle fiber?

Accepted Answer

Once the threshold is reached, the entire muscle fiber contracts fully or not at all.

Question 19

Which of the following would most likely result from a mutation that prevents tropomyosin from moving off actin binding sites?

Accepted Answer

Muscle contraction would be inhibited because myosin could not bind to actin.

Question 20

Which of the following is the correct sequence for the return of a muscle to its relaxed state after contraction?

Accepted Answer

Calcium is reabsorbed into the sarcoplasmic reticulum, troponin and tropomyosin block actin binding sites, ATP binds to myosin causing detachment.

Sliding Filament Theory and Muscle Contraction: Study Notes

Study Guide - Practice Questions