06-Action_potential - BSCI330 Cell biology and physiology...

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BSCI330 – Cell biology and physiology Fall 2009 LAB MANUAL – Lab Exercise #6 Carpenter et al. 2009. BSCI330 Laboratory Manual. University of Maryland, College Park. 1 EXERCISE 6: THE ACTION POTENTIAL In marked contrast to resting potentials, action potentials are a highly specialized electrical property that is characteristic of only a select number of excitable cells . The best examples in our bodies include neurons (the functional cells of nervous tissue) and muscle fibers (the force-producing contractile tissue of the body), although other types exist, such as glandular cells. Signaling by means of regenerative electrical impulses exists in many other multicellular organisms, even some plants—the rapid closing of the carnivorous Venus flytrap is mediated by an electrical action potential event. The primary utility of the action potential is that it is extremely fast , and can be used to communicate signals rapidly between widely separated points to trigger, coordinate and integrate physiological events in the body. Of your primary tissue types, two of them—muscle tissue and nervous tissue—are excitable tissues. Nervous tissue must quickly receive environmental stimuli, process this information, and send out commands. These commands are predominantly received by muscle tissue, which must rapidly carry out the commands of the nervous system. The selective advantage of such signaling is obvious, since the more quickly an organism can sense and respond, the better its chances of survival in an uncertain world. Just these sorts of selective advantages probably drove the evolution of the rapid, stereotyped and regenerative electrical impulse that we call the action potential. As you have learned or will learn soon in lecture, the action potential is the result of the spatiotemporal interaction of the activities of two distinct types of voltage-gated ion channels that are present in the plasma membranes of excitable cells. Keep this in mind as you study the action potential— the event is actually a composite of two separate ionic current events that overlap each other. Although this seems obvious now, it was not always so clear at all. In fact, the original work in the 1940’s by the British neurophysiologists Alan Hodgkin and Andrew Huxley—demonstrating the composite ionic nature of the action potential and providing a mathematical model for the event—was awarded the Nobel Prize. There are not predictions to form for every part of this simulation, but make sure you are recording all information in your lab notebook, as you will definitely asked questions about action potentials on the lab practical. Modeling the Action Potential using the Neurosys program The NEUROSYS computer program was written by Mr. Zayd Eldadah (a former Biology major and BSCI 230 alumnus) and Dr. Herbert Levitan, former Professor of Biology at the University of Maryland. This simulation allows the experimenter to record several properties of an action potential after delivering stimuli of variable intensities (strength and duration) under different environmental conditions.
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This note was uploaded on 12/15/2009 for the course BSCI 330 taught by Professor Payne during the Spring '08 term at Maryland.

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06-Action_potential - BSCI330 Cell biology and physiology...

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