Imagine a postsynaptic neuron is experiencing multiple simultaneous incoming synaptic potentials, which were caused by the activ
ity of several presynaptic neurons. The magnitudes of these synaptic potentials when they reach the postsynaptic cell's axon hillock are given below. Assume the neuron has a normal threshold for firing an action potential that is 15 mV more positive than its resting membrane potential. Based on what you know about spatial summation, will the neuron fire an action potential or not
The missing magnitudes of the synaptic potentials when they reach the postsynaptic cell's axon hillock are:
A. excitatory +7
B. excitatory +10
C. inhibitory -3
D. excitatory +2
E. inhibitory -4
To fire the action potential, the summation of excitatory postsynaptic potentials (EPSP) and inhibitory postsynaptic potentials (IPSP) must reach the action potential threshold, which in this case is 15mV more positive than the resting potential.
The EPSP are: +7 +10 +2= +19
The IPSP are: -3 - 4= -7
EPSP + IPSP=
+19 -7 = +12 mV
The neuron will not fire an action potential since the integration of EPSP and IPSP is below 15mv.
