compound action potential - Zhejiang...
Transcript of compound action potential - Zhejiang...
EXPERIMENT 3Compound action potential of
toad sciatic nerve
Ying-ying Chen, PhDDept. of Physiology, Zhejiang University School of Medicine
bchenyy@zju.edu.cn
EXPERIMENTAL PHYSIOLOGY
IntroductionMembrane potentials
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action potentialResting potential
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The duration of biphasic action potential is dependent on the distance between two recording electrodes
duration
Sciatic nerve: consists of a bundle of nerve fibers
Compound action potential (CAP): resultant recording is the sum of the effect of each of the nerve fibers comprising the trunk
Cross-section of a sciatic nerve
Cell bodies Axons or nerve fibers
Spinal cord
Stimulus artifact: a passive current flow through the extracellular surface of saline-soaked nerve and detected by the recording electrodes, when a stimulus is applied to the nerve
Increase the intensity of
stimulus
threshold stimulus
suprathreshold stimulus
maximal stimulus
Stimulus artifact Action potential
Objectives
To record the CAP of the toad sciatic nerve
To examine the effect of stimulus intensity on the
magnitude of the CAP
To determine the conduction velocity of the CAP
Remove the upper body and internal organs
Remove the skin from both legs
Fix the frog on the frog board with the dorsal surface uppermost
Remove the urostylePlace a thread under the root of the sciatic nerve and ligate itCut the nerve between the knot and the vertebral columnisolate the sciatic nerve
transfer the nerve to the nerve chamber
s1 s2 R1 R2 R3 R4
Stimulating electrodes Recording electrodes
stimulator
nerve
Nerve chamber
Start the softwareClick on the “RM6240USB2.0q(I)(English)” icon on the Desktop Click on the Experiment menu and select the “compound action potential”Select the “Syn trigger” on the Stimulator control panelBreadth =intensity of stimulus
Exercise 1: stimulus and response
Measure the following values:Intensity of threshold stimulus: (V)Intensity of maximal stimulus: (V)
Increase the intensity of
stimulus
threshold stimulus
suprathreshold stimulus
maximal stimulus
Record the following values in a biphasic action potential induced by maximal stimulus:Latency of action potential: (ms)
Action potential duration: (ms)
Peak amplitude of positive phase: (mV)
Peak amplitude of negative phase: (mV)
Latency Duration
Peak amplitude of positive phase
Peak amplitude of negative phase
Exercise 2: conduction velocityV=d/t = (d2-d1)/(t2-t1) (m/s)
d1 or d2: distances Between distal stimulating electrode (S2) and proximal recording electrode
t2
t1s1 s2 R1 R2 R3 R4
d1 d2
Exercise 3:monophasic action potential
Record the following values in a monophasic action potential induced by maximal stimulus : Duration: (ms) Peak amplitude: (mV)
duration
Peak amplitudes1 s2 R1 R2 R3 R4