Final answer:
In Myasthenia Gravis, the transmission of impulses is disturbed at the neuromuscular junction due to autoantibodies blocking acetylcholine receptors, leading to muscle weakness and fatigue.
Step-by-step explanation:
In Myasthenia Gravis (MG), there is a disturbance in the transmission of impulses at the neuromuscular junction. MG is an autoimmune disease characterized by the production of autoantibodies that block the receptors for the neurotransmitter acetylcholine (ACh) on muscle cells. This leads to weakened muscle contractions and can result in paralysis.
The correct answer to the question is a) Neuromuscular junction. Motor neuron axons connect to muscle fibers at this junction, and the synaptic end bulbs of the motor neurons secrete acetylcholine, which binds to receptors on the sarcolemma of the muscle cells. This process is crucial for initiating muscle contraction. In cases of Myasthenia Gravis, the immune system mistakenly attacks the acetylcholine receptors, disrupting this signaling process, and leading to progressive muscle weakness and fatigue.