Human Anatomy & Physiology (9th Edition)

Published by Pearson
ISBN 10: 0321743261
ISBN 13: 978-0-32174-326-8

Chapter 11 - Fundamentals of the Nervous System and Nervous Tissue - Review Questions - Critical Thinking and Clinical Application Questions - Page 426: 1


a. The resting membrane potentials of Mr Miller's cells will become less negative. This means that the the voltage value will rise closer to threshold voltage value ( for example from -70 mV to -45mV) b This makes it easier for threshold value to be reached when a neuron is stimulated. An AP is more easily generated..

Work Step by Step

Normally the concentration of K+ is higher in the ICF than in the ECF, and the concentration of Na+ is higher in the ECF than in the ICF; the Na+/K+ ATPase pump (and the kidneys) maintains these relationships. The K+ drip will overwhelm the ability of the Na+/K+ATPase pump to maintain the normal K+ gradient.. Blood K+ concentration is usually about 4.5mmol/L. As the drip increases the blood [K+] to above 5 mmol/L the ECF potassium moves into the intracellular compartment and the potassium gradient across plasma membranes will decrease-- the inside of the cell will get less negative. This means that the cell will depolarize and the membrane potential will rise closer to the threshold voltage. The consequence of this depolarization for neurons will be that an action potential (AP) will be more easily generated. Initially increase in myocyte [K+} depolarizes the cell and increases myocyte excitability. For cardiovascular health this can pose a threat. Increase in excitability of cardiac myocytes can lead to arrhthymia, and subsequent death by cardiac arrest. The danger of hyperkalemia can be emphasized by pointing out that at one time, prisoners condemned to death, were executed by being given a K+ injection.
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