Biology / Unit 12 Bio 2831 short lesson, about 20 seconds
EPSP, IPSP, and Summation
Captions available
The idea
An excitatory postsynaptic potential depolarizes toward threshold, per Bio 2823; an inhibitory one hyperpolarizes away; summation at the axon hillock combines inputs into one firing decision.
In practice
Multiple weak EPSPs arriving close together can summate into a signal strong enough to cross threshold, even if no single input could.
Where people slip
IPSPs can cancel EPSPs — the net summed voltage determines whether the neuron fires.
Your place on the trail
Every lesson rests on earlier ones and opens later ones. Tap any to jump.
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