regulation of circadian rhythm

Definition

Target type: biologicalprocess

Any process that modulates the frequency, rate or extent of a circadian rhythm. A circadian rhythm is a biological process in an organism that recurs with a regularity of approximately 24 hours. [GOC:dph, GOC:jl, GOC:tb]

The circadian rhythm is an approximately 24-hour cycle in biological processes that is regulated by an internal biological clock. This clock is located in the suprachiasmatic nucleus (SCN) of the hypothalamus, a small region of the brain. The SCN receives light signals from the eyes, which synchronize the internal clock with the external environment. The SCN then sends signals to other parts of the brain and body, regulating various physiological processes, including sleep-wake cycles, hormone production, body temperature, and metabolism.

The regulation of circadian rhythm is a complex process involving multiple interconnected molecular pathways. These pathways involve a network of transcription factors, which are proteins that bind to DNA and regulate gene expression. The core clock genes, including PER, CRY, CLOCK, and BMAL1, play a central role in generating the circadian rhythm.

The expression of these core clock genes oscillates over a 24-hour cycle, with peaks and troughs in their activity. This oscillation is driven by a negative feedback loop:

1. **Transcription and translation:** CLOCK and BMAL1 proteins form a heterodimer that binds to the promoters of the PER and CRY genes, activating their transcription.
2. **Protein accumulation:** The PER and CRY proteins accumulate in the cytoplasm.
3. **Nuclear translocation and inhibition:** The PER and CRY proteins form a complex that translocates to the nucleus, where they inhibit the activity of the CLOCK/BMAL1 complex, thereby reducing the transcription of PER and CRY genes.
4. **Protein degradation:** PER and CRY proteins are eventually degraded, allowing the cycle to begin again.

This negative feedback loop results in a rhythmic expression of the clock genes, which drives the rhythmic expression of other genes involved in the regulation of circadian rhythm.

In addition to the core clock genes, other genes and factors contribute to the regulation of circadian rhythm. These include:

* **Light:** Light is a primary zeitgeber (time giver) that synchronizes the internal clock with the external environment. Light signals are detected by photoreceptor cells in the retina and transmitted to the SCN through the retinohypothalamic tract.
* **Hormones:** Hormones such as melatonin, cortisol, and growth hormone have a role in regulating circadian rhythm.
* **Neuronal activity:** The SCN is composed of a network of neurons that communicate with each other and with other parts of the brain to regulate circadian rhythm.
* **Environmental cues:** Other environmental cues such as temperature, social interactions, and food availability can also influence circadian rhythm.

Disruptions to circadian rhythm, such as from shift work, jet lag, or exposure to artificial light at night, can have negative consequences for health, including increased risk of sleep disorders, metabolic disease, cardiovascular disease, and cancer.'
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Compounds (2,773)