Frog Sciatic Nerve Properties during a Compound Action Potential PDF

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Emma Vasquez BIO 4072 Lab 2: Frog sciatic nerve Frog Sciatic Nerve Properties during a Compound Action Potential Methods: No changes from written lab protocol Results: Experiment 1: Effect of Stimulus Strength

Figure 1: Action potential generated by stimulus just above threshold at 0.13mv

Figure 2: Action Potential generated by a maximal stimulus at 0.25V.

Figure 3: Relationship between stimulus amplitude and action potential amplitude

The goal of Experiment 1 was to determine how the amplitude of the compound action potential varies as a function of stimulus intensity. In order to do this, the threshold stimulus was first found by gradually increasing stimulus strength until an action potential was observed. An action potential was first observed at 0.13 V (Figure 1). Next, the stimulus strength was continually increased until there was no further changes and a maximal stimulation response was observed. This was observed at 0.25 V (Figure 2). Experiment 2: Effect of Stimulus Duration

Figure 4: Relationship between stimulus duration and activation threshold

The goal of experiment was to test the hypothesis that the threshold voltage for stimulating an action potential is dependent upon the duration of stimulating pulse width. In order to do this, the voltage that just barely produces an action potential while stimulus duration was set at 0.10ms was found. This was at 0.2V. Then, the stimulus duration was changed, and the threshold stimulus was found with each new duration setting. Very small changes were made to the pulse width in order to acquire 8 points for strength-duration curve. The rheobase voltage was found 0.2 V. Therefore, the chronaxie is 0.1 ms. Experiments 3 and 4: The effects of temperature on stimulation threshold and conduction velocity

Figure 5: Relationship between temperature on stimulation and conduction velocity

The goal of this experiment was to determine the velocity at which the action potential moves down the sciatic nerve. The conduction velocity is found by measuring the distance between recording electrodes and the time is takes for the action potential to travel that distance. This was all done by connecting a second recording cable to the Powerlab and to a second set of recording electrodes. Therefore, the action potential will be recorded on 2 different channels. The difference in time between each action potential was determined to calculate conduction velocity. The following experiment focused on how the threshold for stimulation and the conduction velocity vary with temperature. This was done by first determining the stimulation threshold at room temperature. Then, the temperature of the nerve was changed by dropping cold 4°C and warm 37°C Ringer’ solution on it. Three action potentials were recorded to calculate the conduction velocity. Experiment 5: Recording polarity Reversing the polarity of the recording electrodes inverses the wave form of the action potential. Experiment 6: Refractory Period As the interval between the two stimuli was shortened, the amplitude of the action potential decreases and the time in which is responds also increase (responds slower). The outer boundary of the relative refractory period begins at 5.5ms gap. The outer boundary of the absolute refractory period is at a 1ms gap....