Basic Neurology Question

Darren darren at
Thu Nov 9 13:49:15 EST 2000

Hello everybody, and first can I say in advance, thank you for any
information that you may provide.

I am currently completing a write-up on an A-level (people in the UK will
know what this is) practical, looking at various attributes of a nerve, in
particular a crab nerve.

One of the experiments is looking at refractory period, by using a series of
electrodes, connected to a computer which sends and records stimuli and
responses. This particular experiment involves sending two impulses through
the nerve at varying intervals ranging from 1ms to 20ms, and then recording
the amplitude of the second response.

My understanding of the theory has led me to understand that the whole idea
is that because the sodium channels in the neurone membrane are not open
until after repolarisation and the resing potential is restored (ie. the
refractory period), the results should show that as the delay between the
stimuli increases, so should the amplitude of the second impulse - having
allowed longer for the refractory period to have completed.

The problem I have is that the results show exactly the opposite, that at
20ms the second response amplitude is 0.014mV and at 1ms it is 0.527mV -
which as far as I can tell is back to front.

My question is, is my theory wrong, is my application of the theory to the
results wrong, or, as I suspect, are my results wrong and actually back to
front ?

Any help will be gratefully appreciated.


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