Autoimmune disruption of neuromuscular transmission

Steps:

• Myasthenia gravis involves autoantibodies targeting acetylcholine receptors at the neuromuscular junction.
• These antibodies block or degrade receptors, reducing acetylcholine binding.
• Initial muscle contractions occur, but repeated stimulation depletes available receptors, causing fatigue.
• This impairs sustained muscle activation without affecting nerve impulse generation.

Why B is correct:

• Autoantibodies limit receptor availability, preventing effective repeated stimulation as defined by neuromuscular transmission failure in autoimmune disorders.

Why the others are wrong:

• A: Muscles are blocked due to impaired transmission, not inability to block.
• C: No permanent stimulation; instead, muscles weaken and fatigue.
• D: Nerves carry impulses normally; the issue is at the junction.

Final answer: B