circadian rhythms.
Not exactly. Circadian rhythms are a subset of diurnal rhythms. Diurnal rhythms reoccur daily and can be circadian and non-circadian. Circadian rhythms can be set by the environment (entrainment), but are not dependent on environment stimulus for continuation (free-running) (ie. hormone secretion). Non-circadian rhythms are responsive to the environment, but still operate on a daily cycle (ie. the process of photosynthesis).
Circadian rhythms
circadian
True. Diurnal rhythms refer to biological processes that follow a 24-hour cycle, while circadian rhythms specifically refer to the body's internal clock that regulates these processes over a 24-hour period. Therefore, diurnal rhythms are a component of circadian rhythms.
daily cycles
epinephrine
yes
Circadian rhythms are a living organisms day/night cycles, daylight interacting with body hormone chemistry.
Biological clocks and circadian rhythms are both mechanisms that regulate physiological processes in organisms based on time. A biological clock refers to the internal timing system that can govern various cycles, including circadian rhythms, which specifically operate on a roughly 24-hour cycle. While both serve to synchronize an organism's functions with environmental cues, biological clocks can encompass a range of time scales (e.g., ultradian or infradian rhythms), while circadian rhythms are strictly tied to the day-night cycle. Ultimately, circadian rhythms are a subset of the broader category of biological clocks.
Melatonin
Circadian rhythms are regulated by the suprachiasmatic nucleus (SCN) in the brain, located in the hypothalamus. The SCN receives input from light-sensitive cells in the retina, helping to synchronize internal body clocks with the external environment.