Betty Kui
Systems Physiology Lab Section 8
Lab 9: Frog Nerve
Abstract
Neurons play an essential role in organisms by delivering electrical synapses
... [Show More] throughout the
body. The purpose of this study is to define and determine biphasic and monophasic action potentials,
action potential threshold, absolute refractory period, relative refractory period, and conduction
velocity of a frog's sciatic nerve. We will explore the concept of compound action potentials (CAP) and
examine the relationship between the strength of a stimulus and its effect on response amplitude of the
2nd CAP.
The sciatic nerve from euthanized Rana catesbeiana, the American bull frog, was used along
with the LabTutor software and PowerLab 15T data acquisition system to test for CAPs. The nerve
bath and PowerLab were set up as specified with diagrams and instructions on LabTutor. The sciatic
nerve was excised with a gross dissection of the frog. Once the nerve was properly isolated, sutures of
different lengths were placed on each end of the nerve to differentiate the proximal and distal ends. The
nerve was then cut and placed in a petri dish of Ringer's solution to remain moist. After the nerve bath
and PowerLab were tested, the nerve was transferred into the nerve bath for experimentation. The first
experiment utilized the sciatic nerve to find the CAP threshold. This was done by first administering
the stimulus voltage at 10mV, and then increasing the voltage by intervals of 10mV until there were
three successive responses that didn't increase in amplitude. The second experiment determined the
absolute and relative refractory periods by gradually decreasing the interval between the stimulus
voltage and the subsequent voltage. The stimulus voltage interval was first set to 4.0 ms and then
decreased to 3.0 ms, 2.5 ms, 2.0 ms, 1.9 ms, and then by steps of 0.1 ms until the interval reached 1.0
ms. For the third experiment, conduction velocity was calculated from measuring the physical distance [Show Less]