Summation (neurophysiology)

Summation, also known as frequency summation is the method of signal transduction between neurons, which determines whether or not an action potential will be triggered by the combined effects of postsynaptic potentials. Neurotransmitters emitting from the terminals of a presynaptic neuron fall under one of two categories. Excitatory neurotransmitters produce further depolarization of the postsynaptic cell, while an inhibitory neurotransmitter will mitigate the effects of an excitatory neurotransmitter. While some neurotransmitters are known to predominately produce one of the two responses, they do widely vary and how they vary ultimately depends on the type of channel to which the neurotransmitter receptor is attached.