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Ok so for a bit of a background, I am doing a science project looking at the action potentials of the earthworm. I anaesthatized the worms then hooked them up to a spiker box (http://backyardbrains.com/products/spikerbox) and stimulated them. This is an average result: Average action potential (they all looked somewhat like this)

What I am confused about is why the action potential goes negative first before then going back up. From my readings online, I thought that the action potentials were meant to go up first then travel down and then continue on its course. If it helps I used a program called audacity to record the action potentials.

Thanks very much guys. Sorry if I'm not being clear. Just ask anything if you need more information!

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1 Answer 1

Nice graph. What happens when you reach the top of the potential (when you depolarize the membrane) that you need to go back to a resting potential to be able to stimulized again. The membrane gets "neutralized" and this reaction often over-shoots and goes below the resting potential, which is quite normal. Before reaching the normal resting potential there will be no further activation. The Wikipedia article on the "Action Potential" contains a more complete explanation.

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This answers why it hyperpolarizes after reaching the peak but why does it hyperpolarize BEFORE the action potential ? –  biogirl Dec 20 '13 at 10:33
In the graph above? My guess would be that two pulses of activation come directly behind each other. –  Chris Dec 20 '13 at 10:44
Sorry for not responding (christmas stuff). @Chris - could you please expand that a bit more? Oh a bit more information about the earthworm incase this influences how it goes negative first: they have 3 main nerve cords carrying the action potentials, 2 of them carrying the signals down the worm and the other transmitting them to the front. Would this at all influence it? –  Jamesg Dec 27 '13 at 10:03
Do you record the impulse from one isolated nerve or is it possible that you record more than one? –  Chris Dec 27 '13 at 10:41
Hm that is possible. Because the equipment I was using was not specifically "designed" for worms (it was designed for cockroaches) I have no way of knowing. If you go to the website that I have put here it has a photo of the pins which you put into the worm. However, if it is true that the results are being influenced by the other nearby nerves sending their signals, why is it the same for all the action potentials I recorded? I have around 50 photos which are almost identical to the one above (length wise). –  Jamesg Jan 18 at 23:53

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