Assume the potentials from the following combinations of dendrites reach the axon hillock/trigger zone at the same time. Which combination will have the greatest chance of generating an action potential?
A) 1, 2, 4
B) 2, 3, 4
C) 3, 4, 5
D) 1, 4, 5

Question

Assume the potentials from the following combinations of dendrites reach the axon hillock/trigger zone at the same time. Which combination will have the greatest chance of generating an action potential? 
A) 1, 2, 4 
B) 2, 3, 4 
C) 3, 4, 5 
D) 1, 4, 5

Quizplus · Accepted Answer

In order to generate an action potential in a neuron, the combined potential of the incoming signals (EPSPs) must reach the threshold potential at the axon hillock/trigger zone. This threshold potential is typically around -55mV. 
Combination 1, 2, 4 has only two dendrites contributing to the signal, while combination 3, 4, 5 has three dendrites, making it more difficult to reach threshold potential. Combination 2, 3, 4 has an inhibitory signal from dendrite 3 which would cancel out some of the excitatory signals from dendrites 2 and 4. 
Combination 1, 4, 5 has the most dendrites contributing to the signal, making it the strongest combination and therefore the most likely to reach threshold potential and generate an action potential.

Assume the Potentials from the Following Combinations of Dendrites Reach