The Signal That Crosses a Synapse Is Stopped When

Multiple Choice

The signal that crosses a synapse is stopped when

A) a second action potential traveling down the signaling cell "sounds a retreat," and the neurotransmitters return to the signaling cell.
B) the responding cell runs out of sodium and is no longer able to respond to the stimulus.
C) the responding cell runs out of potassium and is no longer able to respond to the stimulus.
D) the neurotransmitter is enzymatically broken down or transported back to the signaling cell.