When Sodium moves into the neuron it causes a charge change in the neuron, making it very positive. It repolarizes by pumping sodium back out of the neuron, re-establishing the potential. Neurotransmitters transmit an impulse from one neuron to another chemically. Inhibitory neurotransmitters stop impulses, excitatory neurotransmitters create and encourage impulses. For an action potential to fire the threshold of the input source must be reached.
