After you apply acetylcholine to the muscle fiber, you find that an action potential is generated in the sarcolemma. This result proves that certain events or conditions occur normally within the neuromuscular junction. Which event or condition is NOT PROVED by the above result? Explain your answer. a. ACh receptors are present in the membrane of the motor end plate b. ACh receptors bind to ACh c. Sodium permeability of the end plate membrane is increased d. Acetylcholinesterase breaks down ACh