Our body have its own clock that tick tocks all day long. The circadian rhythm is made up of sets of clocks controlled by brain. Circadian rhythms represents the metabolic, physiological and behavioral vibrations or oscillations that undergoes in human body during 24 hours. These rhythms are controlled by series of functions that influence each and every body part, including the skin.
The Clock that controls rhythms:
The “Main Clock or Master Clock” that controls or vibrates circadian rhythm is present in our brain and consist of approximately 20,000 cells, specifically in suprachiasmatic nucleus (NSQ). The organ regulates the hormonal levels that allow circadian rhythm. NSQ initiates hormonal and neuronal signals, in this way the peripheral organs are functionality synchronized through autonomous clocks present in different cell types.
The simple example of mechanism NSQ and circadian rhythms through hormonal levels is the control of our sleeping and waking cycle.
When there is dark, no light or sunlight or any other artificial source of light, NSQ leads to production of melatonin by the pineal gland and thus high level of melatonin helps us fall asleep.
Similarly, when there is light around us, the light hits the retina and optic nerve of eyes, the production of melatonin stops and body wakes up from sleep.
Circadian Rhythm and Our Skin:
NSQ contacts our skin through various hormones. The oscillators or cell systems found in skin such as pigment producing melanocytes, collagen producing fibroblasts, etc. coordinates with each other and brain’s central clock to drive rhythmic functions in the skin. Circadian rhythm affects the barrier functions, cell recovery, sebum secretion, hydration levels of skin, skin temperature and cell renewal, etc.
During daytime, our skin is very much busy in protecting the skin from UV damage, pollution, oxidation, protecting against external organisms. Transepidermal water loss (TEWL), blood flow and cell proliferation is low during day time. High sebum production, high pH and temperature levels are observed during daytime.
At night, while we sleep, our skin enters in repair mode. It starts growing new skin cells, eliminating damaged cells, delivering fresh blood, oxygen and other nutrients to skin surface. Transepidermal water loss (TEWL) is high at night. Increased sensations such as itching and skin irritations are observed at night.
The circadian rhythm has impact on immediate and long term damage caused by UV radiations. Immediate damage includes DNA damage, erythema and immunosuppression, and long term damage includes photo aging or skin cancer.
Thus going to bed late, using phone and laptops at midnight, eating late, diet, excessive work, stress all these factors leads to changes in circadian rhythm.
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