What do ultradian rhythms signify?

• A. Rhythms that occur on a yearly basis
• B. Bodily rhythms that last longer than 24 hours
• C. Biological rhythms that last less than 24 hours
• D. Infrequent biological rhythms

Answer: (C)

Ultradian rhythms refer to biological cycles that occur more frequently than once a day, typically lasting less than 24 hours. These rhythms can include various physiological and behavioral processes, such as the stages of sleep, hormone release, and appetite cycles, which can repeat multiple times throughout the day. For instance, the sleep cycle comprises multiple stages that repeat every 90 minutes, exemplifying ultradian rhythms in action.

In contrast, rhythms that span a year or last longer than 24 hours do not fit the definition of ultradian. Additionally, infrequent biological rhythms would suggest irregular patterns that do not align with the regularity associated with ultradian cycles. Thus, the focus on cycles lasting less than 24 hours highlights the essential characteristic that defines ultradian rhythms.