Excitatory and inhibitory process
The release of a excitatory neurotransmitter (ACHe) at the synapses will cause an inflow of positively charged sodium ions (Na+) making a localized depolarization of the membrane. The current then flows to the resting (polarized) segment of the axon. Inhibitory synapse causes an inflow of Cl- (chlorine) or K+ (potassium) making the synaptic membrane hyperpolarized. This increase prevents depolarization, causing a decrease in the possibility of an axon discharge. If they are both equal to their charges, then the operation will cancel itself out. There are two types of summation: spatial and temporal. Spatial summation Nerve Synapse requires several excitatory synapses (firing several times) to add up,thus causing an axon discharge. It also occurs within inhibitory synapses, where just the opposite will occur. In temporal summation, it causes an increase of the frequency at the same synapses until it is large enough to cause a discharge. Spatial and temporal summation can occur at the same time as well.