Neurons use chemical signaling mechanisms to communicate with one another. These impulses are transmitted at specialized junctions called synapses. The sending or signaling neuron triggers the release of neurotransmitters (or chemicals) into the synaptic cleft. From there the transmitters bind to receptors on the post synaptic or receiving neuronal cell. These receptors are the gate keepers of neuronal cells and they open and close to send or receive chemicals that signals which direct the actions and reactions of the cell. Chemical synapses can be excitatory or inhibitory. In an inhibitory synapse, binding of the neurotransmitter causes a change in ion permeability that tends to block the generation of opening of the plasma membrane in the receiving cell. For most cases, the binding of an inhibitory neurotransmitter causes a hyper-polarization in closing of the postsynaptic or receiving membrane.