receptors are G protein coupled receptors that activate enzymes, open ion channels, and/or initiate intracellular signaling cascades Metabotropic Luteotropic Phototrophic Exotropic lonotropic The is the gap between the two cells at a chemical synapse. sarcoplasmic reticulum node of Ranvier motor end plate myelin sheath synaptic cleft is a change in a cell's membrane potential that returns it back to its resting potential. Repolarization Hyperpolarization Multipolarization Bipolarization Depolarization.