BIO 350-manusct2

BIO 350-manusct2 - Effect of Elevated External Potassium on...

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Effect of Elevated External Potassium on the Resting Membrane Potential, Effects of ATP and Salts in muscle contraction, and Effects of 5-HT in the Crayfish muscle and in Neuromodulation Cameron Bate 675 Rose St., Department of Biology, University of Kentucky, Lexington, KY 40506-0225 USA Phone: (859) 257-5950, Fax: (859) 257-1717 Email: RLCOOP1@email.uky.edu
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Abstract: 1. Introduction In this experiment the primary focus is on how the external concentration of potassium, , will affect the resting membrane potential in an organism. The membrane potential is created by the difference in electrical charge across a membrane. When the cell membrane is at rest, it is more permeable to potassium, compared to other ions surrounding the membrane. Since there is a leak of potassium through the cell membrane at rest, this must indicate that there is a higher concentration of potassium outside of the membrane while at rest. The resting membrane potential can be closely determined by the Nernst equation. The Nernst equation calculates the potential for movement of a single ion, being potassium in this experiment, across a biological membrane, using a crayfish and its internal membranes. Could this cause higher concentrations of external potassium to have a larger effect on the membrane potential? Especially since the membrane should stay at rest. A rise in the membrane potential of the crayfish muscle is expected, because of the higher extracellular potassium surrounding the membrane. This rise in potassium causes more sodium channels to open, becoming depolarized, and causing the cell to be more excitable (Randall, Burggren, and French 2001). To determine the effect of external potassium on the membrane potentials in an organism, the use of the crayfish, and mainly its abdomen/tail, will serve as a model for the effects of potassium. The overall increase in the external concentration of potassium should result in a decrease in the resting membrane potential, therefore resulting in less negative voltage readings received from the glass electrode that will be used to record voltage.
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The next experiment dealt the effects that the neuromodulator, 5-HT or serotonin, have on the tonic and phasic muscles of the extensor and flexor muscles in the abdomen of the crayfish. The neuromuscular junctions are what this experiment will be, in a way, manipulating and observing the mechanism of these junctions at the muscle. The two neuromuscular junctions to be observed are tonic and phasic nerve junctions in the crayfish abdomen. Tonic motor neurons tend to have more mitochondria, because when stimulated they create a longer lasting effect in muscle, firing for longer periods of time compared to phasic motor neurons. Tonic muscles are involved in muscles dealing with posture, constantly firing, but in a more efficient many, with action potentials being spread out compared to the phasic motor neurons. The tonic neurons tend to fire at a lower intensity, therefore smaller amplitude when observing the recordings in
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This note was uploaded on 03/30/2012 for the course ECO 1111 taught by Professor Xxxx during the Spring '08 term at Kentucky.

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BIO 350-manusct2 - Effect of Elevated External Potassium on...

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