2. Bioelectrodes

Question 1

biopotential electrodes

Answer 1

objective: measure current / potentials in the body
interface between body and apparatus
conduct small current across the interface

Question 2

half cell potential description

Answer 2

potential difference between diff electrolyte regions
- metal placed in electrolyte (ionizable solution), causes distribution of charges & [cations] and [anions] change,
creates pot diff between close-to-electrode electrolyte and elsewhere - separation of charge at the interface -
double electric layer

Question 3

how to measure half cell potential voltage?

Answer 3

• determined by metal involved, [ions] in soln, temp
• not possible to use voltmeter on single electrode, use second metal w half cell potential - H (pot is 0)
• two beakers w metal + H, voltmeter, salt bridge. if current flows to metal: +V, if flows to H: -V
• when 2 metals in same solution: Vnet = Va - Vb

Question 4

electrode circuit

Answer 4

half cell potential, R + C associated with electrode-electrolyte interface, R associated with res in electrolyte

Question 5

problems w half cell potential in biomed field

Answer 5

• half cell potentials can be 1000 times greater than biopotentials, can be issue with biomed instruments
• compensation: diff amps to cancel half cell potential, counter offset voltage, AC coupling to remove DC offset due to hcp

Question 6

metal-electrolyte interface

Answer 6

• interface: current crosses L-R
• Cation reaction - oxidation, cations discharged into -
• electrolyte, e- remain in electrode
• Anion reaction - reduction, anion comes from -
• electrolyte, e- remain in electrode
• makes electrolyte solution near electrode neg
• no current: O = R, electrode to electrolyte: O > R, electrolyte to electrode: R > O

Question 7

electrochem cell, full electrochem cell

Answer 7

ec cell: 2 half cells, each with electrode and electrolyte

fec cell: ions/atoms from one loose e (O) to their electrode, while other gain e (R) from electrode

Question 8

Intracellular recordings (4)

Answer 8

1. microelectrode: capillary glass, insulated metal, solid state multisite recording
2. ECG electrode
3. EEG electrode
4. EMG electrode

Question 9

microelectrodes (3)

Answer 9

• can be inserted into individual bio cells, record AP
  1. capillary glass microelectrode
  2. insulated metal electrode
  3. solid state multisite recording electrode