TRB PG Assistant - Muscle physiology – types, ultrastructure, contraction Online Test (MCQ Quiz)

1. Which of the following is a characteristic feature of skeletal muscle tissue?

A) Involuntary control and branched cells B) Voluntary control and striated appearance C) Involuntary control and spindle-shaped cells D) Voluntary control and smooth appearance

2. Cardiac muscle is primarily found in which part of the body?

A) Walls of the digestive tract B) Biceps and triceps C) Walls of the heart D) Iris of the eye

3. Smooth muscle tissue is characterized by:

A) Multiple peripherally located nuclei and striations B) Single central nucleus and lack of striations C) Branched cells with intercalated discs D) Voluntary control and multinucleated cells

4. The basic contractile unit of a muscle fiber is called the:

A) Sarcomere B) Myofibril C) Sarcoplasm D) Sarcolemma

5. Which protein filament is considered the 'thick' filament in the sarcomere?

A) Actin B) Troponin C) Tropomyosin D) Myosin

6. The 'thin' filaments of the sarcomere are primarily composed of which protein?

A) Myosin B) Actin C) Myoglobin D) Creatine kinase

7. What is the function of the sarcoplasmic reticulum in muscle contraction?

A) To generate ATP B) To store and release calcium ions C) To bind to actin filaments D) To transmit nerve impulses

8. The sarcolemma is the cell membrane of a muscle fiber. What is its specialized name?

A) Endomysium B) Perimysium C) Sarcolemma D) Epimysium

9. Which of the following structures connects a muscle fiber to a motor neuron axon terminal?

A) Synaptic cleft B) Neuromuscular junction C) Motor end plate D) T-tubule

10. The binding of which ion to troponin causes a conformational change, allowing myosin to bind to actin?

A) Sodium (Na+) B) Potassium (K+) C) Calcium (Ca2+) D) Magnesium (Mg2+)

11. What is the role of ATP in muscle contraction, specifically in the 'power stroke'?

A) It binds to myosin, causing detachment from actin. B) It is hydrolyzed to ADP and Pi, releasing energy for the myosin head to pivot. C) It is stored in the sarcoplasmic reticulum. D) It is the primary component of the thin filament.

12. The A band of the sarcomere represents the region containing:

A) Only thin filaments B) Only thick filaments C) Both thick and thin filaments D) The Z-line

13. The I band of the sarcomere contains:

A) Only myosin filaments B) Only actin filaments C) The entire length of myosin filaments D) Regions where thick and thin filaments overlap

14. What is the function of the Z-lines (or Z-discs) in a sarcomere?

A) They anchor the thick filaments. B) They mark the boundaries of a sarcomere and anchor thin filaments. C) They are the region of only thick filaments. D) They contain the enzyme acetylcholinesterase.

15. The H zone within the sarcomere is the central region of the A band containing:

A) Only actin filaments B) Only myosin filaments C) Both actin and myosin filaments D) The Z-line

16. During muscle contraction, the H zone:

A) Shortens B) Lengthens C) Remains the same length D) Disappears completely

17. The sliding filament theory explains muscle contraction as:

A) The shortening of individual thick and thin filaments. B) The sliding of thin filaments past thick filaments. C) The lengthening of the sarcomere. D) The detachment of myosin heads from actin.

18. What neurotransmitter is released at the neuromuscular junction to initiate muscle contraction?

A) Dopamine B) Serotonin C) Acetylcholine D) Norepinephrine

19. The T-tubules (transverse tubules) are invaginations of the sarcolemma that:

A) Store ATP B) Release calcium ions C) Conduct action potentials deep into the muscle fiber D) Anchor the thin filaments

20. Which of the following describes the 'latch state' of smooth muscle?

A) Rapid, forceful contraction B) Sustained contraction with minimal ATP usage C) Rapid relaxation D) Inability to contract

21. Which type of muscle tissue has the ability to regenerate to a limited extent?

A) Skeletal muscle B) Cardiac muscle C) Smooth muscle D) All muscle types regenerate equally

22. What is the primary energy source for muscle contraction?

A) Glucose B) Fatty acids C) Creatine phosphate D) ATP

23. Muscle fatigue is often associated with the depletion of:

A) Myosin B) Actin C) ATP and glycogen D) Calcium ions

24. The 'all-or-none' principle in muscle physiology refers to:

A) The contraction of a single muscle fiber. B) The contraction of a whole muscle. C) The response of a motor unit to a stimulus. D) The release of neurotransmitters.

25. A motor unit consists of:

A) A single muscle fiber and its nerve supply B) A single motor neuron and all the muscle fibers it innervates C) A bundle of muscle fibers D) A sarcomere and its associated proteins

26. Which of the following is a characteristic of slow-twitch (Type I) muscle fibers?

A) High myoglobin content and fatigue resistant B) Low myoglobin content and rapid fatigue C) Primarily anaerobic respiration D) Pale color and fast contraction speed

27. Fast-twitch (Type II) muscle fibers are typically characterized by:

A) High resistance to fatigue and aerobic metabolism B) Low myoglobin content and anaerobic metabolism C) Slow contraction speed and sustained force D) Rich capillary supply and slow ATP hydrolysis

28. What is the role of myoglobin in muscle cells?

A) To bind to actin and initiate contraction B) To store oxygen C) To break down ATP D) To transmit nerve impulses

29. The process by which a muscle fiber generates tension is called:

A) Innervation B) Excitation C) Contraction D) Relaxation

30. What is the state of the myosin head when it is attached to actin and pulling?

A) Energized by ATP hydrolysis B) In the low-energy, detached state C) Bound to troponin D) Ready to bind calcium

31. Which of the following accurately describes the role of tropomyosin?

A) It binds directly to ATP. B) It blocks the myosin-binding sites on actin in a relaxed muscle. C) It is the primary component of the thick filament. D) It is responsible for calcium storage.

32. A single muscle twitch consists of which phases?

A) Contraction and relaxation B) Latent period, contraction, and relaxation C) Excitation and contraction D) Depolarization and repolarization

33. What is tetanus in muscle physiology?

A) A single, brief contraction B) A sustained, forceful contraction due to rapid stimulation C) The relaxation phase of a muscle D) The initial phase of muscle excitation

34. Which type of muscle contraction occurs when the muscle generates tension but does not change length?

A) Isotonic contraction B) Isometric contraction C) Eccentric contraction D) Concentric contraction

35. In concentric isotonic contraction, the muscle:

A) Lengthens while generating tension B) Shortens while generating tension C) Maintains constant length while generating tension D) Relaxes completely

36. Eccentric contraction is when the muscle:

A) Shortens under tension B) Contracts without changing length C) Lengthens under tension D) Contracts maximally

37. What is the function of creatine phosphate in muscle cells?

A) To directly power muscle contraction B) To rapidly regenerate ATP from ADP C) To store oxygen D) To bind to calcium ions

38. The role of acetylcholinesterase at the neuromuscular junction is to:

A) Synthesize acetylcholine B) Break down acetylcholine, terminating the signal C) Bind to acetylcholine receptors D) Inhibit muscle contraction

39. Which of the following is a characteristic of cardiac muscle cells?

A) Voluntary control and multinucleated B) Involuntary control and presence of intercalated discs C) Smooth appearance and spindle shape D) Ability to undergo extensive regeneration

40. Intercalated discs are specialized junctions found in:

A) Skeletal muscle B) Smooth muscle C) Cardiac muscle D) Nerve tissue

41. What is the primary difference between smooth muscle and skeletal muscle regarding control?

A) Smooth muscle is voluntary, skeletal muscle is involuntary. B) Both are involuntary. C) Skeletal muscle is voluntary, smooth muscle is involuntary. D) Both are voluntary.

42. Which protein is responsible for the 'spring-like' action that returns the myosin head to its resting position after ATP binding?

A) Actin B) Troponin C) Tropomyosin D) Myosin

43. The sarcoplasm is the cytoplasm of a muscle cell. What is a key component found in high concentrations within it?

A) Nucleus B) Mitochondria C) Glycogen granules D) Ribosomes

44. Which of the following is NOT a component of the thin filament in a sarcomere?

A) Actin B) Troponin C) Tropomyosin D) Myosin

45. What is the primary function of the M-line in the center of the sarcomere?

A) Anchoring thin filaments B) Anchoring thick filaments and stabilizing the sarcomere C) Containing only thin filaments D) Marking the boundary of the I band

46. The contraction of smooth muscle is generally:

A) Rapid and voluntary B) Slow and involuntary C) Rapid and involuntary D) Slow and voluntary

47. What prevents the thin and thick filaments from sliding back to their original positions during muscle relaxation?

A) The presence of ATP B) The absence of calcium ions C) The binding of troponin to actin D) The release of acetylcholine

48. Which cellular organelle is most abundant in muscle fibers to meet the high energy demands of contraction?

A) Endoplasmic reticulum B) Golgi apparatus C) Mitochondria D) Lysosomes

49. In the context of muscle contraction, the 'rigor mortis' state is characterized by:

A) Complete muscle relaxation due to lack of ATP B) Sustained muscle contraction due to the inability of myosin to detach from actin in the absence of ATP C) Rapid muscle fatigue D) Increased muscle flexibility

50. Which of the following best describes the function of the epimysium?

A) Surrounds individual muscle fibers B) Surrounds fascicles (bundles of muscle fibers) C) Surrounds the entire muscle D) Connects muscle to bone

Muscle physiology – types, ultrastructure, contraction - Online Test

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