What is the term for the rhythmical changes in the body that occur over a 24-hour period?

The term for the rhythmical changes in the body that occur over a 24-hour period is known as a circadian rhythm. This biological process influences various bodily functions, including the sleep-wake cycle, hormone release, body temperature, and other physiological processes that repeat roughly every 24 hours. Circadian rhythms are driven by the internal body clock and are influenced by external cues, particularly light and darkness in the environment.

Understanding circadian rhythms is vital for maintaining overall health and well-being, as disruptions to this natural cycle can lead to various health issues such as sleep disorders and metabolic problems. This concept is distinct from ultradian rhythms, which refer to cycles shorter than 24 hours, and diurnal cycles, which are often used more informally and may not specifically denote the intrinsic biological basis that circadian rhythms encompass. The nocturnal phase typically refers to activities or behaviors that occur at night, but it does not capture the broader context of the 24-hour cycle that circadian rhythms represent.