Measuring Tissue Impedance

Question 1

State body tissues with good conductance.

Answer 1

blood, lymph, spinal liquid, urine.

Question 2

State body tissues with medial conductance.

Answer 2

internal organs, muscle tissues

Question 3

State body tissues with low conductance.

Answer 3

dry skin, bones

Question 4

What kind of resistance do living organisms normally have?

Answer 4

they have high electric resistance, reminding of dielectrics

Question 5

Why do living organisms have high electric resistance?

Answer 5

Due to the property of living organisms whose main constituents are polarized dielectric water molecules.

Question 6

What creates an action potential across the cell?

Answer 6

The cell membrane. The cell has an asymmetric ion distribution due to the selective properties of the membrane.

Question 7

Why does tissue have high resistance?

Answer 7

Due to its capacitance and ohmic resistance.

Question 8

What is capacitance?

Answer 8

The ability of a system to store an electric charge.

Question 9

What is ohmic resistance?

Answer 9

The sum of multiple different types of resistances:

the electrolyte resistance, the resistance of the current collector, the active mass, and the transition resistance between the current collector and active mass.

Question 10

What is impedance?

Answer 10

The total opposition to the flow of current.

Question 11

What is the symbol of impedance

Answer 11

Z

Question 12

What method is based on tissue impedance?

Answer 12

Rheography

Question 13

What is the current when a tissue is put across the A.C. source?

Answer 13

I = U / Z

U = voltage
Z = impedance

Question 14

What is the threshold of perception?

Answer 14

Increasing the current until something is felt.

Question 15

What to do after the tissue reaches the threshold of perception?

Answer 15

double the voltage and connect the resistor R. Adjust R in such a way that the current circuit is the same.

Question 16

What is the final equation used to measure tissue impedance?

Answer 16

R = Z

R = tissue resistance
Z = impedance

Question 17

Explain the procedure of measuring tissue impedance.

Answer 17

1) Connect the circuit.
2) Switch on the generator.
3) Adjust the output voltage at zero value.
4) Set output frequency at 500c/s.
5) Put the rheostat slider position at R=0 Ohms.
6) put two cloths moistened in NaCL solution at 5-10cm separation on the forearm. Then fix electrodes P1 and P2.
7) Switch on and off the knob K each 0.5-1s. Note the voltmeter reading when the person feels the sensation.
8) Adjust the rheostat at 5000 Ohms and double the voltage output.
9) switch off and on K every 0.5-1s, reducing the resistance by moving the rheostat slider to the left until the effect disappears.
10) note the rheostat slider position (resistance value). magnitude = resistance at f=500 c/s.
11) Take measurements of impedance Z at f=2000c/s.
12) Calculate R and C using the following formulae:
I = 2* U / (R+Z)
R = Z
13) Draw conclusions.