Lab4Cockroach1 - Introduction: In this lab, compound action...

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Introduction: In this lab, compound action potentials were recorded from the large ventral central nerve cord in cockroaches in response to sensory stimulation. This sensory stimulation was created by directing puffs of air onto sensory cerci located on the back end of these cockroaches. Neural signals that were recorded in this experiment are created through the movement of ions back and forth across the cell membrane creating waves of electrical depolarization. Within a neuron, there is a resting membrane potential where there is no net flow of ions in or out of the membrane. This resting membrane potential is around -70mV. There is more K+(potassium) inside the cell and more Na+ (sodium) outside of the cell. This negative membrane potential is due to the fact that the Na+/K+ pump, pumps 3 Na+ out of the cell for every 2 K+ inside the cell. During a depolarization however, a sequence of events happen which lead to an electrical depolarization. To begin, there is some type of sensory stimulation, which elicits the opening of a few Na+ channels allowing Na+ to rush into the membrane making it more positive. These few channels in turn activate multiple adjacent Na+, which allows for a threshold to be reached in order to elicit an action potential. This threshold must be reached in order for an action potential to occur. This process is referred to as ‘all or none.’ Either the threshold is reached and there is an action potential or the threshold is not reached and there is no further activity. After an influx of Na+ and action potential is fired and the Na+ channels are closed. The closing of these channels leads to the activation of K+ which pumps K+ out of the cell. Pumping K+ out of the cell allows the cell to become more negative allowing the neuron to regain its resting membrane potential. There is a
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slight hyperpolarization due to the delay of closing the K+ channels and then once the K+ channels are closes the resting membrane potential is once again achieved. Refer to the diagram below for a visual representation of the events (NSCI BOOK). The goal of this experiment was to record the joint activity in the nerve by observing compound action potentials. Neurons send action potentials down long processes known as axons. Axons from multiple neurons are grouped together forming whole nerves. Recording from the whole nerve allows us to record the sum of electrical activity of all the action potentials being transmitted along that nerve at any particular time. The following questions were generated to address the role of cerci and compound action potential activity: QUESTION: What is the difference in motor response to puffing air on the left side
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versus puffing air on the right side?
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Lab4Cockroach1 - Introduction: In this lab, compound action...

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