Circadian Rhythm: Definition, Function, & Examples

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Circadian Rhythm Definition

Circadian is a Latin word where “diem” means day and “circa” means around. Circadian rhythm, it’s a biological rhythm, which is cyclic and an organized way in which organism reacts to a particular stimuli. There are other biological rhythms like the Infradian rhythm, ultradian rhythm and diurnal rhythm.

Ultradian rhythms are cyclic rhythms which lasts for a smaller period less than 24 hours, whereas Infradian rhythm last for more than 24 hours. A variant of circadian rhythm is diurnal rhythm which occurs in the day and night cycle.

What is Circadian Rhythme?

Biological rhythms are usually endogenous, which means controlled by a biological clock, from inside, whereas rhythms can be exogenous as well which requires zeitgeber. However, circadian rhythms are endogenous, which generates a 24 hour long cyclic and synchronized pattern.

Circadian rhythm are said to be in a rhythmic fashion when it possess the following features, which are;

  • Temperature reparations.
  • 24-hour rhythm which is endogenous.
  • A rhythm which can be reset due to environmental changes and 24hour synchronization.

In the hypothalamus, suprachiasmatic nuclei, circadian clock is found which drives the circadian rhythm and is present in humans and mammals. If this clock is damaged or dysfunctional it can have a huge impact on the daily chores of an individual and their health.

Thus, it may result in a circadian rhythm disorder, which can be circadian rhythm sleep disorder, which disrupts the sleep cycle. It can be due to environmental conditions, medical conditions, genetics, ageing and other reasons.

Circadian Rhythm Examples

a) Nyctinasty: Plants sleeps in the night and get up in the morning. Here the plants dangle out as they are sleeping. For instance, legumes, and in the night they crimp their leaves.

b) Cognitive performance: Due to their cognitive performance, they are quite on guard in the day time. When their role is reversed, those animals are called as nocturnal.

c) Daily rhythms in body temperature: humans have a particular variation in the body temperature that during the day time its high and while night time its low. This is the pattern observed.

d) Sleep wake cycle: Sleep wake cycle is associated with the melatonin production, during the day and night time. Suprachiasmatic nuclei in the hypothalamus, produces melatonin, which results in sleep as it is dark. This is seen in human.

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