During a neural impulse, a neuron "fires" when
a) it is physically contacted by another cell that is transmitting the signal.
b) an electric charge travels down the axon.
c) it contracts and releases powerful chemicals directly into the bloodstream.
d) signals entering at the axon travel the length of the cell and exit through the dendrites.
e) neurotransmitters attach to the dendritic receptors.
Answer: B