Question 1

Which protein is responsible for providing elasticity and stabilizing the thick filament in the sarcomere?

Accepted Answer

Titin

Question 2

During the sliding filament theory, what is the immediate effect of ATP binding to the myosin head?

Accepted Answer

Myosin releases actin

Question 3

Which of the following best describes the role of the T-tubules in skeletal muscle fibers?

Accepted Answer

Transmit action potentials deep into the muscle fiber

Question 4

A patient presents with muscle fatigue after short-duration maximal exertion. Which of the following is a likely cause?

Accepted Answer

High extracellular potassium ($$K^+)$$

Question 5

Which muscle type is characterized by single, tapered cells, gap junctions, and the ability to contract without depolarization?

Accepted Answer

Smooth muscle

Question 6

What is the primary function of the sarcoplasmic reticulum in muscle fibers?

Accepted Answer

Storing and releasing calcium ions ($$Ca^{2+})$$

Question 7

Which of the following best explains why slow-twitch muscle fibers are more resistant to fatigue?

Accepted Answer

They have more mitochondria and myoglobin

Question 8

In the context of muscle contraction, what is the role of troponin?

Accepted Answer

Binds calcium ions to initiate contraction

Question 9

Which of the following is true regarding the 'all-or-none' principle in motor units?

Accepted Answer

All muscle fibers in a motor unit contract if the motor neuron fires

Question 10

A muscle is held at a constant length while generating force. What type of contraction is this?

Accepted Answer

Isometric

Question 11

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

Accepted Answer

Action potential → ACh release → nAChR activation → Na$$^+$$ influx → SR Ca$$^{2+}$$ release → contraction

Question 12

Which of the following is a distinguishing feature of cardiac muscle compared to skeletal muscle?

Accepted Answer

Presence of intercalated discs

Question 13

Which molecule acts as a temporal and spatial buffer for ATP in muscle cells during intense activity?

Accepted Answer

Phosphocreatine

Question 14

What is the main reason that fast-twitch glycolytic fibers fatigue more quickly than slow-twitch fibers?

Accepted Answer

They rely primarily on anaerobic metabolism

Question 15

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

Accepted Answer

Aligns actin filaments

Question 16

A muscle fiber is stimulated repeatedly with high-frequency action potentials, resulting in a sustained contraction with no relaxation. What is this phenomenon called?

Accepted Answer

Fused tetanus

Question 17

Which of the following is true regarding the length-tension relationship in skeletal muscle?

Accepted Answer

Maximum tension is generated when there is optimal overlap between actin and myosin

Question 18

Which of the following is a unique feature of smooth muscle contraction compared to skeletal muscle contraction?

Accepted Answer

Contraction can occur without an action potential

Question 19

Which of the following best describes the role of the DHP receptor in excitation-contraction coupling?

Accepted Answer

Acts as a voltage sensor to trigger Ca$$^{2+}$$ release from the SR

Question 20

Which of the following is the correct order of muscle organization from largest to smallest?

Accepted Answer

Muscle → fascicle → fiber → myofibril → sarcomere

Chapter 12: Muscles – Structure, Function, and Physiology

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