Determination of the conduction velocity and duration of the action potential of the sciatic nerve trunk

Summary

The experimental method was obtained from the official website of the Fourth Military Medical University

Operation method

Determination of conduction velocity and duration of the action potential of the sciatic nerve trunk

Principle

Peripheral nerves have the function of transmitting information, and the carrier for accomplishing this conduction function is the action potential in the conduction of nerve impulses, and the excitability of the nerves after excitation will change regularly with time. Therefore, the measurement of the presence or absence of action potentials, conduction velocity and excitability can understand the functional state of the nerve. It has certain clinical significance. Using the method of recording action potentials to determine the distance and time taken by the nerve impulse, the conduction velocity of the nerve impulse can be calculated. Using a series of double-pulse stimulation, by changing the length of the interval between the two stimuli of the double stimulation. Observe the response of the nerve trunk to the stimulation again after the excitation. You can understand the pattern of change of excitability.

Materials and Instruments

Toad or Frog
Frog Surgical Instruments Ren's Solution Electrical Stimulator Oscilloscope Specimen Case

Move

I. The preparation of sciatic nerve trunk specimens refers to the experiment: Sciatic nerve trunk maneuvers Potential guidance and recording

Setting up and connection of the apparatus 1. Commissioning Oscilloscope Scanning speed Conduction speed lmS/Div
Should not period 5mS/Div
The rest is the same as above. Sciatic Trunk Movement Potential Guidance and Recording Stimulator Conduction speed Refer to experiment: Potential guidance and recording of sciatic nerve trunk movements. TheShouldn't be too long.
Stimulation mode Continuous double
Stimulation period 0.125 S
Stimulation intensity Maximum stimulation
Wave Width Min.
Delay Large to small
2. Connections Connect the instrument according to Figure 1-3, but the signal is two-way, see Figure 2-1.

Experimental Steps and Observation Items 1. Firstly, action potentials were induced from the two pairs of recording electrodes by maximal stimulation.2. Using an oscilloscope cursor, measure the latency t1 at the first recording electrode and t2 at the second recording electrode, and the time between the peaks of the negative phase waves of the two action potentials, T. Measure the distances from the stimulating electrodes to the first recording electrode, s1, and to the second recording electrode, s2, using the ruler in the specimen box.

3. Method I for calculating the conduction velocity of nerve trunk action potentials:

V =s1/tl or V =s2/t2
4. Method II for calculating the conduction velocity of nerve trunk action potentials:
V = (s2-s1)/(t2-t1)
5. method III for calculating the rate of conduction of action potentials in the nerve trunk:
V = (s2-s1)/T
6. Observe and record the differences in amplitude, time course, and shape of the action potentials guided by the two pairs of recording electrodes. Refer to Figure 2-2.

7. Remove the scanning line of the latter recording electrode, adjust the instrument, and measure the period of inactivity. The stimulus intensity is selected as the maximum stimulus, and two artifacts and their elicited action potentials can be seen before and after.
8. Adjust the delay knob to shorten the time between the double stimulation waves and observe the change in the amplitude of the action potential caused by the second stimulus.
9. When the second action potential disappears, and no second excitation can be induced even if the stimulus intensity is increased, use the oscilloscope cursor to read out the time between the two artifacts, i.e., the absolute period of inappropriateness (approximate value).
10. Adjust the intensity of the stimulus, observe and record the period of inappropriateness at different intensities.

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