Explain the difference between spatial and temporal summation at a synapse.

-Spatial summation occurs when multiple presynaptic neurones together release enough neurotransmitter (e.g. acetylcholine) to exceed the threshold of the postsynaptic neurone. For example, neurone A and neurone B may individually release insufficient neurotransmitter but when these quantities are combined, threshold may be exceeded and an action potential generated. 

-Temporal summation occurs when one presynaptic neurone releases neurotransmitter many times over a period of time. The total amount of neurotransmitter released may exceed the threshold value of the postsynaptic neurone. The higher the frequency of the action potential the more quickly the threshold may be exceeded.