Question 1

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

Accepted Answer

It stores and releases calcium ions ($$\mathrm{Ca$$^{2+}$$}) to $$trigger muscle contraction.

Question 2

A patient is unable to relax their muscles after contraction. Which protein is most likely malfunctioning?

Accepted Answer

Sarcoplasmic reticulum $$\mathrm{Ca$$^{2+}$$}$$ pump

Question 3

Which event directly triggers the release of acetylcholine (ACh) from the motor neuron at the neuromuscular junction?

Accepted Answer

Opening of voltage-gated $$\mathrm{Ca$$^{2+}$$}$$ channels in the neuron terminal

Question 4

During the contraction phase of a muscle twitch, which of the following occurs?

Accepted Answer

Cross-bridge cycling between actin and myosin increases muscle tension.

Question 5

Which of the following best explains why a muscle fiber produces maximal tension at an optimal sarcomere length?

Accepted Answer

There is maximal overlap between actin and myosin filaments, allowing the greatest number of cross-bridges to form.

Question 6

Which muscle fiber type would be most active during a marathon race?

Accepted Answer

Slow oxidative (Type I)

Question 7

A drug blocks ligand-gated sodium channels on the motor end plate. What is the most immediate effect?

Accepted Answer

End plate potential (EPP) will not be generated, preventing muscle contraction.

Question 8

Which process provides the fastest way for a muscle cell to regenerate ATP during the first few seconds of intense activity?

Accepted Answer

Transfer of a phosphate from creatine phosphate to ADP by creatine kinase: $$\mathrm{ADP + CP \xrightarrow{CK} ATP + C}$$

Question 9

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

Accepted Answer

Isotonic contractions involve a change in muscle length, while isometric contractions involve a change in tension without a change in length.

Question 10

A muscle fiber is repeatedly stimulated before it can fully relax. Which phenomenon is most likely to occur?

Accepted Answer

Wave summation leading to unfused tetanus

Question 11

Which of the following is a function of myoglobin in skeletal muscle fibers?

Accepted Answer

It binds and stores oxygen, enhancing aerobic ATP production.

Question 12

Which of the following best explains the size principle of motor unit recruitment?

Accepted Answer

Smaller motor units are activated first, followed by larger units as more force is needed.

Question 13

Which of the following is true regarding the role of ATP in cross-bridge cycling?

Accepted Answer

ATP binding to myosin causes the cross-bridge to detach from actin.

Question 14

A patient has a genetic mutation that prevents the production of troponin. What is the most likely consequence?

Accepted Answer

Muscle contraction cannot be regulated by $$\mathrm{Ca$$^{2+}$$}$$, leading to impaired contraction.

Question 15

Which metabolic pathway is most important for providing ATP during a 30-minute jog?

Accepted Answer

Oxidative phosphorylation in mitochondria

Question 16

Which of the following is a characteristic of fast glycolytic (Type IIb) muscle fibers?

Accepted Answer

They fatigue quickly and generate high force using anaerobic metabolism.

Question 17

Which of the following best describes the sequence of events in excitation-contraction coupling?

Accepted Answer

Action potential → $$\mathrm{Ca$$^{2+}$$}$$ release from SR → Troponin binds $$\mathrm{Ca$$^{2+}$$}$$ → Tropomyosin moves → Cross-bridge cycling

Question 18

Which of the following would most likely increase the force generated by a skeletal muscle?

Accepted Answer

Increasing the number of active motor units (motor unit recruitment)

Question 19

Which of the following is true regarding the relaxation phase of a muscle twitch?

Accepted Answer

$$\mathrm{Ca$$^{2+}$$} is $$actively transported back into the sarcoplasmic reticulum.

Question 20

Which of the following best explains why endurance training increases muscle fatigue resistance?

Accepted Answer

It increases the number of mitochondria and capillaries, enhancing aerobic ATP production.

Skeletal Muscle System Physiology: Structure, Function, and Mechanisms

Study Guide - Practice Questions