When an action potential reaches the axon terminal: neurotransmitter molecules are released from the axon terminal and bind to receptors on the postsynaptic neuron, causing either an inhibitory hyperpolarization or an excitatory depolarization. sodium ions are released from the axon terminal, enter the cell body of the postsynaptic neuron through its sodium channels, and may initiate an action potential in that neuron. calcium ions are released from the axon terminal, bind to and open the sodium channels on the cell body of the next neuron, and may initiate an action potential in that neuron. neurotransmitter molecules are released from the axon terminal, bind to and open the potassium channels on the cell body of the next neuron, and may initiate an action potential in that neuron.