For this experiment, the sciatic nerve of a bullfrog is dissected out and used for experimentation and observation. The nerve will be used to test and measure extracellular readings of CAP at threshold stimulus, refractory periods, and conduction velocity. This should allow for a better understanding on the interpretation of compound action potentials. The purpose of this experiment is to test effects of stimulus on a bullfrog’s sciatic nerve to see the relationship between threshold, refractory periods, and conduction velocity from compound action potentials.
Materials and Methods
I. A Sciatic Nerve Dissection
A double-pithed bullfrog is taken and secured to a dissecting board. To be able to dissect the frog, it had to be anesthetized…show more content… For LabTutor, the first and second sets of recording electrodes are connected to the nerve bath as shown in the diagram. The BNC connectors of the stimulating electrode leads are connected to the outputs on the PowerLab hardware. Ringer’s solution is then added to the nerve chamber to a point about 1mm from the bottom without touching the electrodes or it could cause a short circuit in the experiment. The setup is tested with a strip of filter paper moistened with 0.16 M NaCl laid across the electrodes. LabTutor stimulates and recorded data and shows system to be working correctly. The sciatic nerve that was removed is placed in the nerve chamber length-wise and covered to prevent the nerve from drying out.
A. Eliciting the Compound Action Potential
The sciatic nerve is first used to determine the threshold voltage and maximal CAP amplitude. In LabTutor, the stimulus voltage is first set to 10 mV and the nerve will be stimulated and recorded for a period of 5 ms after a 1 ms delay. The stimulus voltage is increased by increments of 10 mV. Each stimulation is recorded until there are three successive responses that didn’t increase in amplitude or a stimulus voltage of 400 mV is reached.
B. Refractory