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ELEC 383: Introduction to Biosensors and Bioinstrumentation
MID-TERM EXAMINATION

DATE: October 30, 2009 TIME: 19:00 pm - 20:30 pm
PLEDGE OF HONOR
On my honor as a student of Hong Kong University of Science and Technology, I have neither received aid from others nor given aid to others while taking this exam. All of the answers represent my own work.
Signature: __________________ Date: ________________
Student Name:


Student Number:

Total: 20 pts. + 2 pts. (bonus)
(Please make your answers short and each answer should not be over three sentences.)
1. (4 pts.) Generally, biomedical signals can be described as random processes.
a.
List four basic methods to study the properties of biomedical signals.

b.
Estimate the frequency distribution of following EEG waves.

c.
If the averaged amplitudes of the four EEG waves are the same, which signal is the most difficult to detect? Why?

d.
EEG signal is mainly contributed from the electrical activities of granular neuron cells. True? False? Why?



2. (7 pts.) BIOPOTENTIAL
Action potentials originate from the opening of ion channels and reflect the biological activity of cells.
a.
What are the major factors affect the movements of ion across the cell
membrane?


b.
The difference in sodium ion concentrations between intracellular and extracellular fluids is the major factor to determine the amplitude of action potential. True? False? Why?

c.
Assuming that the membrane potential of pacemaker cell is determined entirely by the sodium and potassium ions at equilibrium state, find the resting membrane potential of the pacemaker cell based on following information:


[K+]extracellular=6 mEq/L; [K+]intracellular=180 mEq/L
[Na+]extracellular=150 mEq/L; [Na+]intracellular=50 mEq/L
Ratio of the potassium and sodium permeability = Pk/PNa = 6
RT/F = KT/q= 0.0615 at 37 C

d.
Suppose that the firing threshold of the cells is C 20 mV. Assuming that Pk remains constant, what is the minimum amount that PNa would need to change to fire the action potential?

e.
Explain why the propagation of an action potential can be modeled as a traveling electrical dipole.


3. (4 pts.) ELECTROCARDIOGRAPHY SIGNALS
Suppose that the locations of the RA, LA and LL electrodes form an equilateral triangle on the chest as shown below.
. Define Lead I, II , III, aVR, aVL and aVF.

LL
.
There are several times during the cardiac cycle at which the voltages measured on Lead I, II and III are zero at the same time even though the heart is contracting. Explain the origin(s) of this phenomenon.

.
It is really necessary to measure only two of the three standard ECG leads (I, II, III) because the third can be calculated from the other two. True? False? Why?

.
Explain the function of driven right leg circuit in ECG measurement.


4. (4 pts) The drawing below represents a small piece of partially depolarized ca