1. What two events facilitate the fast repolarizing (hyperpolarizing) phase of the action potential?

2. (a) Why are action potentials most likely initiated at the axon hillock/axon initial segment? (b) What experiment approach could one use to test this idea?

3. Why does broadening the presynaptic action potential (making it wider) increase the size of the post-synaptic excitatory post-synaptic potential?

4. In our local circuit, GABAB receptors are present on the presynaptic terminal of GABAergic synapses. Activation of GABAB receptors acting via adenylyl cyclase inhibits activation of voltage-gated Ca2+ channels in response to presynaptic action potentials. (a) Activation of these GABAB receptors in our local circuit would have what general effect on the postsynaptic neuron? (b) Why?

5. What are the two factors need to occur for to allow Ca2+ influx through NMDA receptors?

6. Why is the endocannibinod system considered a retrograde signaling pathway? What does activation of the endocannibinod system generally do to presynaptic release probability (Pr)?