A Closer Look
The circadian rhythm, present in humans and most other animals, is generated by an internal clock that is synchronized to light-dark cycles and other cues in an organism's environment. This internal clock accounts for waking up at the same time every day even without an alarm clock. It also causes nocturnal animals to function at night when diurnal creatures are at rest. Circadian rhythms can be disrupted by changes in daily schedule. Biologists have observed that birds exposed to artificial light for a long time sometimes build nests in the fall instead of the spring. While the process underlying circadian rhythm is still being investigated, it is known to be controlled mainly by the release of hormones. In humans, the internal clock is located within the brain's hypothalamus and pineal gland, which releases melatonin in response to the information it receives from photoreceptors in the retina. Nighttime causes melatonin secretion to rise, while daylight inhibits it. Even when light cues are absent, melatonin is still released in a cyclical manner.
Words nearby circadian rhythm
How to use circadian rhythm in a sentence
Sometimes a column has the economy and rhythm of a short story.
Royal Christmases have a rhythm and routine—but this year Will, Kate, and baby George have their own, more relaxed plans.
A car parked at a red light honked its horn in rhythm with the chant as the crowd passed in front of it.
Most rhythm sections play pretty straight, but we were pushing him, the way we were with Miles.
I never got a definitive answer, but I think he was used to having a rhythm section that would not be that dynamic under him.
The significance of time is determined by the movement of any selection, or, in other words, the rhythm.
The reason we associate rhythm with the significance of time is that rhythm is a measurer of time.
The rhythm of a simple tune plays favourably on a child's ear, enhancing life according to this great law.Children's Ways|James Sully
Much more attention should be given than is ordinarily devoted to the consideration of rhythm.
Their music is entirely of a light character, but they have rhythm and grace in a remarkable degree.Music-Study in Germany|Amy Fay
Cultural definitions for circadian rhythm
An activity cycle lasting twenty-four hours. Many living things, including humans, follow a circadian rhythm. (See biological clock.)