Synapse

Illustration of a nerve impulse passing from one neuron to another in the intrasynaptic space. The action potential arrives in the presynaptic terminal (yellow synaptic terminal button). The transmitter is synthesised in the vesicles. When the presynaptic terminal is depolarised, the calcium channel opens (orange receptor on the synapse). The Ca2+ enters the channel and leads to fusion between the vesicles and presynaptic membrane. The transmitter is freed into the synaptic clefts and attaches to its receptor located in the postsynaptic membrane (blue receptor). The opening and closing of the calcium channels leads to a modification in the membrane potential; either a depolarisation or hyperpolarisation can then occur (if depolarisation is large enough, it can lead to action potential). (Photo by: BSIP/Universal Images Group via Getty Images)