Question

Which receptors are blocked in Myasthenia Gravis?

• A. Acetylcholine (ACh) receptors
• B. Ca++ receptors
• C. Na2+ receptors
• D. Opioid receptors

Hint:

Autoantibodies attack the post-synaptic nicotinic receptors at the NMJ.

Answer 1

The Correct Option is A

Step 1: Myasthenia gravis is an autoimmune disorder of the neuromuscular junction. The body produces antibodies directed against the nicotinic acetylcholine receptors (AChRs) on the post-synaptic membrane of skeletal muscle. Step 2: These antibodies block and destroy AChRs and cause loss of the post-junctional folds, so even though acetylcholine is released normally, the muscle cannot respond effectively. This produces fatigable muscle weakness that worsens with activity and improves with rest. Step 3: Because the defect is a shortage of working AChRs, giving an anticholinesterase (such as neostigmine or edrophonium) raises synaptic acetylcholine and transiently improves strength - the basis of the diagnostic Tensilon test and of treatment. Step 4: The distractors (calcium, sodium and opioid receptors) are not the autoimmune target here, so option (a), acetylcholine receptors, is correct.