Final answer:
Myasthenia gravis is an autoimmune disorder that blocks acetylcholine receptors, causing muscle weakness. The disease progresses from drooping eyelids to overall muscle weakness and fatigue. Myasthenia crises can occur, affecting breathing and requiring emergency care.
Step-by-step explanation:
Myasthenia gravis is an autoimmune disorder where circulating antibodies block the nicotinic acetylcholine receptors on the motor endplate of the neuromuscular junction. This blockage of acetylcholine receptors leads to muscle weakness, starting with symptoms like drooping eyelids and progressing to overall muscle weakness and fatigue. In advanced cases, myasthenia crises can occur, which can affect the muscles controlling breathing and require emergency medical care.