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)
What cardiac activity ocurs in the P wave?
Depolarisation of the atria
What cardiac activity ocurs in the QRS complex?
Depolarisation of ventricles
What cardiac activity ocurs in the T wave?
Repolarisation of ventricles
What is a unipolar/Wilson-type lead?
Where the RA, LA and LL electrodes are connected to a point of constant potential. (Indifferent Electrode)
Profile of an alpha wave
Resting phase of the brain (Coma/sleeping)
8-13 Hz
Profile of a beta wave
Brain activity when counting/learning
> 13 Hz
Profile of a delta wave
Deep sleep, lesions in brain
0.5-3.5 Hz
Profile of a theta wave
Induced by LSD, play role in cognitive processes
4-7 Hz
What are ECGs and EEGs recorded on?
Cathode-Ray Oscilloscope
Give the two methods of short-wave diathermy
Capacitance and inductance methods
In the capacitance method, the heat produced by dissipated kinetic energy is…
proportional to the square ofthe current (joule heating)
The inductance method uses an inductor, this produces… in the body
eddy currents
How does microwave diathermy work?
Tissue absorbes electromagnetic waves.
Radiation produced in a magnetron
