Describe and explain how a signal is transmitted between neurones.

Action potential arrives down the first neurone. The action potential is a changing potential as a result of ion channels opening along the walls of the neurone, with Na+ moving in down the electrochemical gradient, creating a 40mV potential. At the end of the neurone, this potential changes the shape of the Ca2+ channel proteins, opening the channel, and allowing Ca2+ to flow in. The Ca2+ binds with the vesicles, making the vesicles bind to the membrane of the neurone. The acetylcholine in the vesicle then diffuses across the synaptic cleft, and attaches to Na+ channel proteins at the Post synaptic neurone. This opens the channels, and creates an action potential flowing down the neurone. This is called a synapse.