Explain how an action potential is transmitted from one neurone to another at a synapse.

A good answer would start with a definition of a synapse ('the junction between two neurones') and then be formatted as bullet points or numbers for clarity and backed up with a diagram.Action potential arrives at presynaptic neurone This causes voltage-gated Ca++ channels to open in the presynaptic neuroneCa++ enters presynaptic neurone, causing vesicles containing neurotransmitters to move to, and fuse with, the presynaptic membrane (by exocytosis), releasing the neurotransmitters into the synaptic cleftNeurotransmitters diffuse across the synaptic cleft and bind to neurotransmitter receptors on the postsynaptic membraneIf the neurotransmitter is excitatory, this will cause positive ions (e.g. Na+, K+, Ca++) to enter the postsynaptic neuroneThe result is a depolarisation of the postsynaptic neuroneIf the postsynaptic neurone is depolarised above the threshold potential, this elicits an action potential in the postsynaptic neurone (all-or-nothing rule)