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Excitable Cells - Lecture 11 (06/03/2018)
The flow of charged ions generates a current, which can be measured using electrical recording equipment. These measurements are made on physiological samples.
Electrophysiological recordings are made to record extremely fast (sub-millisecond timescale upwards) and extremely sensitive (as little as one ion channel), with good spatial resolution.
These allow the details of individual channels to be dissected, such as the activation,
inactivation and pore properties.
Types of Recordings:
Not specific, as it cannot measure the activity of a single neurone or single cell, giving superficial information.
Suited for the clinic.
Electrodes are usually placed on the head, and these measure the areas of activity in the brain directly under each electrode, with the same principle as an ECG and ERG.
Difficult to perform.
Suited for the lab to measure neuron activity.
Usually the electrode is pushed through the cell membrane into the cell.
These can target specific neurones, but not the individual channels.
Very difficult to perform.
Suited for the lab to measure channel activity.
This technique uses a blunted pipette, which cannot go through the membrane, so instead it is sealed onto the membrane so that there is no leakage of current.
The aim is to isolate a single channel underneath the patch.
Neher and Sakmann were awarded the Nobel prize in 1991 for inventing the patch technique in order to investigate how current spreads along neurones and measure how synapses degrade and action potentials propagate.
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