1. When the stimulus intensity is increased, what changes: the number of synaptic vesicles released or the amount of neurotransmitter per vesicle? 2. What happened to the amount of the neurotransmitter release when you switched from the control extracellular fluid to the extracellular fluid with no Ca2+? 3. What happened to the amount of neurotransmitter release when you switched from the extracellular fluid with no Ca2+ to the extracellular fluid with low Ca2+? 4. How did neurotransmitter release in the Mg2+ extracellular fluid compare to that in the control extracellular fluid? 5. How does Mg2+ block the effect of extracellular calcium on neurotransmitter release?