Lecture 11 Flashcards
What is used to measure membrane potential?
Electrophysiological Methods (With microelectrodes)
Potential Sensitive staining (Optical spectroscopy)
What is a microelectrode composed of?
Glass capillary with a conducting wire immersed in it
Why is the microelectrode made of Ag/AgCl?
To avoid distruving electrolysis
Why is the electrolite of the microelectrode usually KCl?
To avoid potential formation between the two solutions
What is the voltage-clamp technique?
A measuring device continuously monitors membrane potential, an additional current is added to balance any effect of a membrane change.
What is the key element and function of the voltage clamp circuit?
The Operational amplifier
Causes a full negative feedback
What is the patch clamp technique?
A small patch of membrane is seperated, the currents in this patch are measured.
Which chemical can be used to block Na+ channels in the patch pipette technique?
TTX (Tetrodotoxin)
Give two kinds of dye which are used for optical measurement of membrane potentials
Electric potential sensitive dyes
Electrically charged dyes
How do electrically charged dyes work?
If membrane potential changes, so will the dye distribution.
Membrane potential is then calculated with the Nernst eqation.
The distribution of the dyes must be…
Homogeneous and uniform
Not forming polymers or binding to cell organelles
Give three biopotentials on the body surface
Electromyogram
Electrocardiogram
Electrocephalogram
Give the pathway for depolarisation of cardiac muscles.
SA Node - depolarises both atria
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AV node - depolarises both ventricles
The potential values measured on the body surface are dependent on…
The location of the electrodes
The triangular shape of the three ECG leads on the chest is called the…
Einthoven Triangle
Standard limb leads (bipolar lead)
