Select the correct statement with respect to disorders of muscles in humans.
- Failure of neuromuscular transmission in myasthenia gravis can prevent normal swallowing.
- Accumulation of urea and creatine in the joints causes their inflammation.
- An overdose of vitamin D causes osteoporosis.
- Rapid contractions of skeletal muscles cause muscle dystrophy.
Answer
(1) Failure of neuromuscular transmission in myasthenia gravis can prevent normal swallowing.
Solution
(1) Correct: as per NCERT, myasthenia gravis is an auto-immune disorder affecting the neuromuscular junction, leading to fatigue, weakening and paralysis of skeletal muscle. Swallowing needs skeletal muscles of the mouth and pharynx, so it can be affected.
(2) Incorrect: gout (inflammation of joints) is due to accumulation of uric acid crystals, not urea and creatine.
(3) Incorrect: osteoporosis is an age-related disorder of decreased bone mass; decreased levels of estrogen are a common cause.
(4) Incorrect: muscular dystrophy is the progressive degeneration of skeletal muscle, mostly due to a genetic disorder.
Answer: (1)