Biology (11th Edition)

Published by McGraw-Hill Education
ISBN 10: 1-25918-813-2
ISBN 13: 978-1-25918-813-8

Chapter 43 - The Nervous System - Review Questions - Synthesize: 4

Answer

Karen's cells have become habituated to caffeine, needing more of it to stimulate them to the same degree as before.

Work Step by Step

Habituation is common with repeated stimuli (imagine listening to waves at the beach--you brain eventually "turns them off"). This can happen with chemicals like caffeine and is common in drug addicts who take things like cocaine and marijuana.
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