Question

Active learning: A possible wiring diagram for synapses • Excitatory synapses in green • Inhibitory synapses in red • Which reaches the dendrite first, excitation or inhibition? . Will the excitation be long lasting or short lasting? Why?

Answer 1

1. excitation reaches the dendrite first.

Basically, a postsynaptic neuron adds together, or integrates, all of the excitatory and inhibitory inputs it receives and “decides” whether to fire an action potential.

Action potential +40 Voltage (mv) EPSPs add up to produce threshold depolarization Threshold Resting state EPSP EPSP 0 1 4 5 2 3 Time (ms)

2.   For instance, let’s suppose that excitatory synapses are made on two different dendrites of the same postsynaptic neuron, as shown below. Neither synapse can produce an EPSP quite large enough to bring the membrane potential to threshold at the axon hillock—the place where the action potential is triggered, boxed below. If both subthreshold EPSPs occurred at the same time, however, they could sum, or add up, to bring the membrane potential to threshold.