Experiment 3: FROG NERVE
(LAB TUTOR)
Herrera, M. | Macatingrao, S. | Padilla, J. | Tan, M.
Group 10
4b6
INTRODUCTION
Photo Retrieved from: https://step1.medbullets.com/neurology/113052/action-potential-basics
Compound Action Potentials
METHODOLOGY
Dissection
Nerve Bath
Photo retrieved from https://openwetware.org/wiki/Lab_9:_Conduction_Velocity_of_Nerves
Exercise 1: threshold voltage and maximal cap amplitude
Set the
stimulus
voltage to 10mV
Click START to
stimulate the
nerve
Click the UP arrow
in the Stimulator
Panel to increase
stimulus voltage
by 10 mV and then
click START
Repeat step 3
until you reach
a stimulus
voltage of
400mV
Exercise 2: refractory period
Set the Stimulus voltage
to the minimum voltage
required to elicit a
maximal CAP (Exercise 1),
then set stimulus interval
to 4.0ms
Click START to
stimulate the nerve
twice at the selected
interval
Repeat steps 2 & 3,
decreasing the interval
to 3.0ms, 2.5ms, 2.0ms,
1.9ms, and then by steps
of 0.1ms until the interval
between the stimuli
reaches 1.0ms
Decrease the interval
in Stimulator Panel to
3.5ms then click START
Exercise 3: conduction velocity
Enter in the stimulator
panel, a voltage that is
twice the one used in
Exercise 2
Click START
The absolute refractory period starts
at 1.3ms while the relative refractory
period starts at 1.8ms
conclusion
Exercise 1
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Exercise 2
Exercise 3
Threshold voltage and maximal CAP amplitude of the frog’s sciatic nerve
The nerves require a minimum voltage of 130 mV to elicit a compound action
potential
However the amplitude of the CAP would not increase not until the maximal
stimulus voltage was reached.
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The Absolute refractory period starts at 1.3 ms stimulus interval
The Relative refractory period starts at 1.8 ms stimulus interval
This shows that after the beginning of the action potential, the sodium and/or
calcium channels become inactivated at 1.8 ms stimulus interval
○ no signal that could open the inactivated gates
●
The conduction velocity of the frog’s sciatic nerve was measured to be 125 m/s
○ Higher than the normal range for a frog’s nerve fiber in the lab = 40 m/s.