Myasthenia gravis primarily affects which part of the body?

Myasthenia gravis primarily affects the neuromuscular junction, which is the critical site where nerves communicate with muscles. In this condition, the immune system produces antibodies that block or destroy nicotinic acetylcholine receptors at the neuromuscular junction. This impairs the ability of acetylcholine, a neurotransmitter, to stimulate muscle contraction, leading to weakness and fatigue of the voluntary muscles.

The hallmark of myasthenia gravis is muscle weakness that worsens with activity and improves with rest. Symptoms often include ocular abnormalities, such as ptosis (drooping of one or both eyelids) and diplopia (double vision), as well as weakness in other muscle groups, including those involved in swallowing and breathing.

Understanding myasthenia gravis at the neuromuscular junction level is crucial for recognizing and managing this condition, making the neuromuscular junction the correct answer. Other options like the spinal cord, cerebral cortex, and peripheral nerves are not directly involved in the pathophysiology of myasthenia gravis, as the primary dysfunction lies specifically at the neuromuscular junction.