At a chemical synapse, a neurotransmitter molecule, such as acetylcholine, communicates a signal from one neuron, the presynaptic cell, to another, the postsynaptic cell. Neurotransmitter molecules are stored in vesicles in the presynaptic neuron. Some vesicles dock by a specific docking proteins at the presynaptic terminal. An electric impulse, called an action potential, arrives at the synaptic terminal and docked vesicles fuse with the presynaptic membrane, dumping neurotransmitter into the synaptic cleft. Neurotransmitter binds receptors on the postsynaptic cell, which, depending on the specific receptor and cell type, open or close ion channels. Thus, the action potential passes to the new cell. The empty vesicles are recycled via endocytosis of clathrin-coated pits and take up more neurotransmitter to start the cycle again.