Compound Action Potential Lab Report

Much like cells are the fundamental unit of a living being, neurons are the fundamental unit of the nervous system. These neurons work together with other excitable cells to produce action potentials when they receive electrical or chemical stimuli. Action potentials can be thought of as an “all-or-nothing” event and occur as a large-scale depolarization when sodium and other positive ions rapidly enter the neuron through membrane channel proteins. Once initiated, action potentials travel down the length of the axon and when it reaches the end a neurotransmitter is released into the synapse. Neurotransmitters work differently and some can act to inhibit the neurons while others activate them. After the action potential is complete, the neuron must repolarize and go through a refractory period. During this time the neuron is incapable of producing another action potential (Stillman, 2005). In this lab, compound action potentials (CAPs) will be measured from an isolated sciatic nerve from a cane toad, Bufo marinus. Compound action potentials are the total sum of action potentials from the multitude of neurons that compose a nerve (Stillman, 2005).
The absolute and relative refractory periods will be found by stimulating the nerve with a series of pulses. The velocity of the compound action potential as it travels down the nerve will then be calculated to determine the nerve conduction velocity. Lastly, the temperature sensitivity of nerve conduction velocity will be tested by measuring the speed at which the compound action potential travels down the nerve at both hot and cold temperatures. It was hypothesized that threshold voltage, maximal CAP amplitude, refractory period, nerve conduction velocity and temperature sensitivity of nerve conduction velocity would be