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+}$$}) $$necessary for muscle contraction.

Question 2

A patient is diagnosed with myasthenia gravis. Which of the following best explains the physiological basis of their muscle weakness?

Accepted Answer

Autoantibodies block acetylcholine receptors at the neuromuscular junction, reducing muscle fiber stimulation.

Question 3

During a muscle contraction, which event occurs immediately after acetylcholine binds to receptors on the motor end plate?

Accepted Answer

An action potential is generated along the sarcolemma.

Question 4

Which of the following best explains the 'all-or-none response' in muscle fibers?

Accepted Answer

A muscle fiber contracts completely or not at all when stimulated above threshold.

Question 5

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

Accepted Answer

Action potential travels along sarcolemma $$\rightarrow T-$$tubules depolarize $$\rightarrow$$ Calcium released from sarcoplasmic reticulum $$\rightarrow$$ Troponin binds calcium $$\rightarrow$$ Tropomyosin shifts $$\rightarrow$$ Myosin binds actin

Question 6

A marathon runner experiences muscle cramps during a race. Which of the following is the most likely physiological cause?

Accepted Answer

Depletion of ATP and accumulation of lactic acid leading to sustained muscle contraction.

Question 7

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

Accepted Answer

It breaks down acetylcholine, terminating the signal for muscle contraction.

Question 8

Which of the following muscle fiber types is most resistant to fatigue and is primarily used for endurance activities?

Accepted Answer

Type I (slow oxidative) fibers

Question 9

A muscle is unable to relax after contraction, resulting in a state known as tetany. Which of the following best explains this phenomenon?

Accepted Answer

High-frequency stimulation prevents calcium from being reabsorbed into the sarcoplasmic reticulum.

Question 10

Which of the following best describes the function of creatine phosphate in muscle contraction?

Accepted Answer

It donates a phosphate group to ADP to rapidly regenerate ATP during the initial seconds of intense activity.

Question 11

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 filaments.

Question 12

Which of the following is the correct order of connective tissue layers from the outermost to the innermost in a skeletal muscle?

Accepted Answer

Epimysium $$\rightarrow$$ Perimysium $$\rightarrow$$ Endomysium

Question 13

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

Accepted Answer

It binds calcium ions, causing a conformational change that moves tropomyosin and exposes myosin-binding sites on actin.

Question 14

A sprinter relies on the phosphagen system for energy during a 100-meter dash. Which equation best represents the reaction catalyzed by creatine kinase in this system?

Accepted Answer

$$\mathrm{Creatine\ phosphate + ADP \rightarrow Creatine + ATP}$$

Question 15

Which of the following best explains the concept of 'oxygen debt' after strenuous exercise?

Accepted Answer

It is the extra oxygen required to restore metabolic conditions to resting levels, including replenishing ATP, creatine phosphate, and converting lactic acid to glucose.

Question 16

Which of the following best describes the arrangement of fascicles in a pennate muscle?

Accepted Answer

Fascicles are short and attach obliquely to a central tendon.

Question 17

Which of the following is a characteristic unique to cardiac muscle tissue compared to skeletal and smooth muscle?

Accepted Answer

Presence of intercalated discs for synchronized contraction.

Question 18

Which of the following best describes the function of myoglobin in muscle fibers?

Accepted Answer

It stores oxygen for use during periods of high metabolic demand.

Question 19

A muscle fiber is observed to have a high number of mitochondria, abundant myoglobin, and contracts slowly. Which type of muscle fiber is this most likely to be?

Accepted Answer

Type I (slow oxidative) fiber

Question 20

Which of the following best explains why the I band of a sarcomere shortens during muscle contraction?

Accepted Answer

Thin filaments slide past thick filaments, reducing the region containing only thin filaments.

Muscle Structure, Function, and Physiology: Key Concepts and Definitions

Guida di studio - Domande di pratica

Study guide - Flashcard