Discussions of how hormones influence behavior have generally been limited to the effects of gonadal hormones on reproductive behavior and have emphasized the parsimonious arrangement whereby the same hormones involved in the biology of reproduction also influence sexual behavior. It has now become clear, however, that other hormones, in addition to their initiated when deviations from normal are quite small, thereby maintaining plasma osmolality within relatively narrow ranges.
In the osmoregulation of body fluids, the movement of water across cell membranes permits minor fluctuations in the concentration of solutes in extracellular fluid to be buffered by corresponding changes in the relatively larger volume of cellular water. Nevertheless, the concentration of solutes in extracellular fluid may at times become elevated or is, only after osmotic dehydration exceeds the capacity of the animal to deal with it physiologically.
What this question is testing
Your task
Identify why the author included the referenced detail at that point in the passage — its function, not its content.
Common trap
Answers that merely repeat or summarize the topic of the detail instead of describing the role it plays.
Winning move
Ask what job the detail does for the paragraph, then for the passage's broader point.
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