EEG (electroencephalography) signal intensity EEG is a method to monitor neural
ID: 1551767 • Letter: E
Question
EEG (electroencephalography) signal intensity EEG is a method to monitor neural activities in the brain. Many electrodes are placed on the head (see the figure in the right) to measure electrostatic potential. Let's consider one such electrode and the magnitude of the signal measured by the electrode. (a) First, for a axon of radius 0.5 mu m, calculate the total electric charge that flows into the axon when an action potential is generated. Assume that Na^+ can flow into the axon only through the node of whose length is 1 mu m. (b) Assuming that the total electric charge carried by the Na^+ at action potential generation is distributed over a small volume (like a point-charge), calculate the electrostatic potential due to this net electric charge at the distance of 1 cm from the center of the charge distribution.Explanation / Answer
a) Electric field can be given as :
E = kQ/r2
k = 8.99×109 Nm2/c2
Q= 1.6×10-19 C
r= 0.5×10-6m
By putting values :
E = (8.99×109)(1.6×10-19)/(0.5×10-6)2= 5753.6 N.C
b) electrostatic potential can be given as:
V = KQ/r = (8.99×109)(1.6×10-19)/(1×10-2)= 1.44×10-7 v
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