Question

One treatment option for acquired myasthenia gravis is acetylcholinesterase inhibitors. Select the most correct description of how this treatment helps to alleviate the symptoms.

A: blocks the enzymatic breakdown of ACh receptors, restoring normal numbers and neuromuscular activity to normal

B: increases the break down of acetylcholine (ACh), reducing the need for ACh receptors on the post-synaptic membrane

C: stimulates the release of acetylcholine (ACh) from pre-synaptic vesicles

D: blocks the enzyme that breaks down acetylcholine (ACh), increasing the amount of ACh available at the neuromuscular junction

Answer 1

Myasthenia gravis is an autoimmune disorder affected skeletal muscles wherein there are antibodies against Acetylcholine receptors present on neuromuscular junction. As a result ACh (acetylcholine) cannot bind to AChR is defective, inhibiting the muscle contraction.

Acetylcholinesterase is an enzyme that breaks down ACh. Inhibitors of Acetylcholinesterase will inhibit the acetylcholinesterase enzyme at synapse. As a result, ACh is not degraded. This will result in increased binding of ACh to AChR. Hence, symptoms of MG can be overcome.

Acetylcholinesterase has no effect on ACH receptor or on release of ACh from pre-synaptic vesicle of motor neuron.

Right choice: D: blocks the enzyme that breaks down acetylcholine (ACh), increasing the amount of ACh available at the neuromuscular junction.