Flashcards in Snail electrophysiology Deck (20)
On a microscope what does the focus knob do ?
it enables you to focus the image of the specimen
it is used to move the lens closer and further away from the specimen to get a sharp image
what is the amplifier used for ?
it is used to measure the resistance of the recording electrode and adjust the bridge balance of the electrode
what is the micromanipulator used for ?
to maneuver the electrode into place before impaling a neuron
what is the difference between the F1 and A1 pins ?
F1 pins are much smaller and finer than the A1 pins because the F1 pins are used to pin down the brain whereas the A1 pins are used to pin down the snail
what are the stages in the siphon principle for perfusing the snail brain ?
1- fill a beaker with hepes saline
2- attach a syringe to one end of the tube
3- stick other end of tube into the beaker of hepes saline and place on shelf in faradays cage
4- secure tube with blue tack
5- apply suction through the tube using syringe and then remove syringe and the saline should be flowing through the tube
6- once there is flow in the tube the pin is placed in the preparation near the electrode
7- using tissue paper place it at the edge of the bath to prevent overflow of saline
8- once the sink is full it is drained using a syringe
what is an example of a ganglion from lymnaea stagnalis?
left pedal ganglion
why is pronase added to the preparation bath before intracellular recordings take place?
to remove and soften the inner connective tissue sheath to alow the recording electrode to impale the cell
what solution was the intracellular recording electrode filled with ?
potassium sulphate - K2SO4
what is the bridge balance ?
the bridge balance is set up to compensate for the large electrode resistance so that the voltage reading obtained from the neurons is the actual membrane voltage of those neurons
why is the electrode resistance so large ?
for measuring membrane voltages of neurons a microelectrode is used to enable us to electrically contact the cytoplasm, however the electrode needs to be very small and sharp to penetrate the cell without killing it or causing major damage and this is what causes the large electrode resistance
what does the clean switch on the amplifier do ?
it is used to unblock the electrode, the electrode is often blocked when the resistance is too high
what does too low a resistance indicate ?
it indicates the tip is broken and needs to be discarded
once you have the recording electrodes in contact with the cell, how is impalement bought about ?
tapping the base plate- this will cause slight vibrations enough to allow the electrode to impale the cell without damaging it too much
what do you do after impalement of your neuron ?
switch off the illuminator to prevent the preparation over heating
what is ohms law?
V=I x R
what can affect the input resistance of a cell ?
it is affected by ion channels
what does the input resistance of a neuron reflect ?
reflects the extent to which membrane channels are open
what does a low input resistance represent ?
high conductance and open channels
what does a high input resistance represent ?
low conductance and closed channels