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(ELEC383)[2009](f)midterm~ee_jmx^_10329.pdf
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ELEC383 2009 Fall Midterm Exam Solution
Question 1
(a). Mean, Variance, Autocorrelation, and power spectral density, etc.
(b). Alpha wave: 8-13Hz Beta wave: 14-30Hz Theta wave: 4-7Hz
Delta wave: <3.5Hz
/(.f)1/2
(c). We use Vmaxto indicate the difficulty of measurement. For fixed amplitude
/(.f)1/2
signals, larger bandwidth can get a smaller Vmaxvalue which meaning it is harder to be measured. Therefore, beta wave is the most difficulty to measure.
(d). False. EEG denotes the potential fluctuations recorded from the brain. The recorded fluctuating potentials represent a superposition of the potential of millions of neurons arising from synaptic activity in the brain synchronously. Whats more, granular cells are small and radially arranged. The generated potential will be cancelled each other.
Question 2
(a)
Diffusion gradients; the inwardly directed electrical field; the membrane structure; the active transport of ions against elecctro-chemical gradient.
(b)
True. The difference of sodium ion concentration between intracellular and extracellular fluids does determine the amplitude of action potential. Another factor is the ion channel property (e.g. permeability). The action potential of a cell is the consequence of sudden change of permeability of the cell membrane to sodium ions.
(c)
Use Goldmans equation:
(d)
If Vm-20mV, calculate the PK/PNa.
Therefore,
(e)
Because of the flow of current, potential are created. And potential may be determined by considering the separate effects of source I and . I at distance r and r , or by
00 10
rr
considering the effects of a dipole of magnitude p = I 0 d at distance r .
Question 3
(a)
(b)
The periods in a cardiac, during which the voltages measured on Lead I, II and III are
zero, are called P-R segment and S-T segment. The P-R segment is due to the function of
atrioventricular node (AV node) that receives the wave of depolarization, delays it and
dispatches it to the AV bundle. The S-T segment is the period of slow repolarization of
the ventricles.
(c)
True. Lead II = Lead I + Lead III.
(d)
The driven right leg circuit in ECG measurement gives common-mode feedback to
the differential-input amplifier to cancel or alleviate the noise from the measurement
environment, such as 50Hz power line noise.
Question 4
The potential induced at three points are as follows:
Where 1=180, 2=110, 3=0, Therefore, ,
Lead I signal VAB= .2-.1=5.89*10-4 mV, Lead II signal VAB= .3-.1=1.29*10-3 mV.
Question 5
(a) Half-cell potential: Electrolyte surrounding the metal is at a difference electric potential from the rest of the solution. The half-cell potential is
where the solubility Ks and the potential of Ag are constants.
Cl
In the biological fluids the concentration of . ions is relatively high (not related to the oxidation of Ag), therefore t