MCQs on Skeletal Muscle, Muscle Contraction, Neuromuscular Junction, Joints, Rheumatoid Arthritis, Osteoporosis, and Gout

1. The functional contractile unit of skeletal muscle is:

A. Myofibril
B. Sarcolemma
C. Sarcomere
D. Fascicle

Answer: C. Sarcomere

2. Which band remains unchanged in length during skeletal muscle contraction?

A. A band
B. I band
C. H zone
D. Z line

Answer: A. A band

Explanation: The length of thick filaments does not change during contraction.

3. The protein responsible for binding calcium during muscle contraction is

A. Tropomyosin
B. Troponin C
C. Troponin I
D. Myosin

Answer: B. Troponin C

4. Which structure anchors thin filaments in a sarcomere?

A. M line
B. H zone
C. Z line
D. A band

Answer: C. Z line

5. During maximal contraction of skeletal muscle, which structure may disappear?

A. A band
B. Z line
C. H zone
D. Sarcolemma

Answer: C. H zone

6. ATP is directly required for:

A. Exposure of active sites on actin
B. Calcium release from SR only
C. Detachment of myosin head from actin
D. Troponin activation

Answer: C. Detachment of myosin head from actin

7. In rigor mortis, muscles become stiff because:

A. Excess ATP is present
B. Calcium is absent
C. Myosin cannot detach from actin due to ATP depletion
D. Actin is destroyed

Answer: C. Myosin cannot detach from actin due to ATP depletion

8. The immediate source of calcium for skeletal muscle contraction is:

A. Extracellular fluid
B. T-tubules
C. Sarcoplasmic reticulum
D. Mitochondria

Answer: C. Sarcoplasmic reticulum

9. Which protein has ATPase activity in skeletal muscle?

A. Actin
B. Troponin
C. Tropomyosin
D. Myosin head

Answer: D. Myosin head

10. The triad of skeletal muscle consists of

A. One T-tubule and two terminal cisternae
B. Two T-tubules and one terminal cisterna
C. Three T-tubules
D. Sarcolemma and SR

Answer: A. One T-tubule and two terminal cisternae

11. The sequence of events during contraction is correctly represented as:

A. ATP hydrolysis - Ca²⁺ release - Cross-bridge formation
B. Ca²⁺ release - Troponin activation - Cross-bridge formation
C. Cross-bridge formation - Ca²⁺ release - ATP hydrolysis
D. Troponin activation - Ca²⁺ release - Cross-bridge formation

Answer: B. Ca²⁺ release - Troponin activation - Cross-bridge formation

12. The I band contains:

A. Thick filaments only
B. Thin filaments only
C. Thick and thin filaments
D. No filaments

Answer: B. Thin filaments only

13. The neurotransmitter released at the neuromuscular junction is:

A. Dopamine
B. Acetylcholine
C. GABA
D. Norepinephrine

Answer: B. Acetylcholine

14. Acetylcholine acts on which receptor at the motor end plate?

A. Muscarinic M2 receptor
B. Nicotinic Nm receptor
C. Nicotinic Nn receptor
D. β2 receptor

Answer: B. Nicotinic Nm receptor

15. The enzyme responsible for rapid degradation of acetylcholine in the synaptic cleft is:

A. Monoamine oxidase
B. Catechol-O-methyltransferase
C. Acetylcholinesterase
D. Choline acetyltransferase

Answer: C. Acetylcholinesterase

16. Which ion triggers exocytosis of acetylcholine from the presynaptic terminal?

A. Sodium
B. Potassium
C. Calcium
D. Chloride

Answer: C. Calcium

17. Myasthenia gravis primarily affects:

A. Presynaptic calcium channels
B. Acetylcholine synthesis
C. Postsynaptic nicotinic receptors
D. Acetylcholinesterase activity

Answer: C. Postsynaptic nicotinic receptors

18. Botulinum toxin causes paralysis by:

A. Blocking nicotinic receptors
B. Inhibiting acetylcholine release
C. Increasing acetylcholine degradation
D. Blocking calcium uptake into SR

Answer: B. Inhibiting acetylcholine release

19. Lambert-Eaton syndrome is characterized by antibodies against:

A. Nicotinic receptors
B. Acetylcholinesterase
C. Voltage-gated calcium channels
D. Sodium channels

Answer: C. Voltage-gated calcium channels

20. Fibrous joints are joined by:

A. Cartilage
B. Synovial fluid
C. Fibrous connective tissue
D. Ligaments only

Answer: C. Fibrous connective tissue

21. An example of a primary cartilaginous joint is

A. Intervertebral disc
B. Pubic symphysis
C. Epiphyseal plate
D. Knee joint

Answer: C. Epiphyseal plate

22. The knee joint is classified as a

A. Fibrous joint
B. Cartilaginous joint
C. Synovial joint
D. Syndesmosis

Answer: C. Synovial joint

23. Functionally, synarthrosis refers to

A. Freely movable joint
B. Slightly movable joint
C. Immovable joint
D. Saddle joint

Answer: C. Immovable joint

24. Which joint permits movement in a single plane?

A. Ball-and-socket joint
B. Hinge joint
C. Saddle joint
D. Condyloid joint

Answer: B. Hinge joint

25. The shoulder joint is an example of

A. Pivot joint
B. Saddle joint
C. Ball-and-socket joint
D. Plane joint

Answer: C. Ball-and-socket joint

26. The atlantoaxial joint is a

A. Pivot joint
B. Hinge joint
C. Condyloid joint
D. Saddle joint

Answer: A. Pivot joint

27. Rheumatoid arthritis is primarily a

A. Degenerative disease
B. Autoimmune inflammatory disease
C. Metabolic disease
D. Infectious disease

Answer: B. Autoimmune inflammatory disease

28. The characteristic pathological lesion of rheumatoid arthritis is:

A. Tophus
B. Osteophyte
C. Pannus
D. Bouchard node

Answer: C. Pannus

29. Which joint involvement is most characteristic of rheumatoid arthritis?

A. Distal interphalangeal joints
B. First metatarsophalangeal joint only
C. Symmetrical involvement of small joints
D. Vertebral joints only

Answer: C. Symmetrical involvement of small joints

30. Rheumatoid factor is most commonly

A. IgG against IgM
B. IgM against Fc portion of IgG
C. IgA against IgG
D. IgE against collagen

Answer: B. IgM against Fc portion of IgG

31. The most specific laboratory marker for rheumatoid arthritis is

A. ESR
B. CRP
C. Anti-CCP antibody
D. Rheumatoid factor

Answer: C. Anti-CCP antibody

32. Osteoporosis is characterized by:

A. Defective mineralization of bone
B. Increased bone mass
C. Reduced bone mass with normal mineralization
D. Excess cartilage formation

Answer: C. Reduced bone mass with normal mineralization

33. The gold standard diagnostic investigation for osteoporosis is:

A. X-ray
B. MRI
C. DEXA scan
D. CT scan

Answer: C. DEXA scan

34. A T-score of −2.5 or below indicates:

A. Normal bone density
B. Osteopenia
C. Osteoporosis
D. Osteoarthritis

Answer: C. Osteoporosis

35. Postmenopausal osteoporosis is primarily related to deficiency of

A. Growth hormone
B. Estrogen
C. Testosterone
D. Cortisol

Answer: B. Estrogen

36. Which cell is mainly responsible for bone resorption?

A. Osteoblast
B. Osteocyte
C. Osteoclast
D. Chondrocyte

Answer: C. Osteoclast

Gout

37. Gout is caused by deposition of

A. Calcium phosphate crystals
B. Calcium oxalate crystals
C. Monosodium urate crystals
D. Cholesterol crystals

Answer: C. Monosodium urate crystals

38. The most common site of the first acute gout attack is:

A. Hip joint
B. Knee joint
C. First metatarsophalangeal joint
D. Shoulder joint

Answer: C. First metatarsophalangeal joint

39. Hyperuricemia results from increased levels of:

A. Urea
B. Uric acid
C. Creatinine
D. Bilirubin

Answer: B. Uric acid

40. Needle-shaped, negatively birefringent crystals are seen in

A. Rheumatoid arthritis
B. Osteoarthritis
C. Gout
D. Septic arthritis

Answer: C. Gout

41. Which enzyme is inhibited by allopurinol?

A. Cyclooxygenase
B. Lipoxygenase
C. Xanthine oxidase
D. Carbonic anhydrase

Answer: C. Xanthine oxidase

42. Tophi are

A. Cartilaginous nodules
B. Osteophytes
C. Deposits of monosodium urate crystals in tissues
D. Fibrous tumors

Answer: C. Deposits of monosodium urate crystals in tissues

43. Assertion (A): During muscle contraction, the length of actin and myosin filaments remains constant.

Reason (R): Muscle contraction occurs due to sliding of filaments past each other.

A. Both A and R are true, and R explains A
B. Both A and R are true, but R does not explain A
C. A is true, R is false
D. A is false, R is true

Answer: A

44. Assertion (A): Osteoporosis predisposes to fractures.

Reason (R): Bone mineralization is defective in osteoporosis.

A. Both true and R explains A
B. Both true but R does not explain A
C. A true, R false
D. A false, R true

Answer: C

Explanation: Mineralization is normal in osteoporosis; bone mass is reduced.

45. Assertion (A): Myasthenia gravis causes muscle weakness.

Reason (R): Autoantibodies destroy nicotinic acetylcholine receptors at the NMJ.

A. Both A and R are true, and R explains A
B. Both true but R does not explain A
C. A true, R false
D. A false, R true

Answer: A

Memory-Based One-Liners

46. The protein masking myosin-binding sites on actin is

A. Troponin
B. Tropomyosin
C. Titin
D. Nebulin

Answer: B. Tropomyosin

47. Freely movable joints are termed

A. Synarthrosis
B. Amphiarthrosis
C. Diarthrosis
D. Syndesmosis

Answer: C. Diarthrosis

48. Most abundant purine end product in humans

A. Urea
B. Uric acid
C. Creatinine
D. Ammonia

Answer: B. Uric acid

49. The hallmark cytokine involved in rheumatoid arthritis is

A. IL-4
B. TNF-α
C. Erythropoietin
D. Gastrin

Answer: B. TNF-α

50. The power stroke during muscle contraction is produced by

A. ATP binding to myosin
B. Release of ADP and Pi from myosin head
C. Calcium binding to actin
D. Sodium influx into muscle

Answer: B. Release of ADP and Pi from myosin head

Dr. Alok Singh