Final answer:
The internal and external voltage charge of the postsynaptic neuron is dealt with by ligand-gated ion channels.
Step-by-step explanation:
The internal and external voltage charge of the postsynaptic neuron is dealt with by the ligand-gated ion channels. Neurons have charged membranes due to different ion concentrations inside and outside the cell. When neurotransmitters bind to postsynaptic receptors, these ion channels open, allowing ions to flow into or out of the neuron, changing the membrane potential and generating postsynaptic potentials.