Today we did a very interesting experiment on Cockroach leg samples to understand action potential. Cockroach leg was secured on a foam block using two electrodes. These two electrodes were placed across the Coxa such that there is significant amount of tissue gap between them.
Figure source: http://www.entomologa.ru/figures/22.htm
After this we stimulated the leg with a square wave generated from signal generator. Peak to peak voltage greater than 300 mV. We varied the frequency of stimulation first from 0.5 Hz to upto 10 Hz and back down to about 1 Hz. We could see the matching leg flip activity with each stimulated pulse.
We also tried to see the reverse effect where we acquired the action potential induced due to tapping at the leg. For this we removed the stimulation line and only acquired the signals from oscilloscope. So whenever there was a small tap on the end of the leg we could see a distinct induced potential on the scope.