How does light impact our circadian rhythm?
Light works in setting our circadian rhythm as a Zeitgeber—German word for “life giver”–in that is tells your body what time of day it is and therefore, what it should be doing. There are other Zeitgebers, the most important of which are social interaction and food intake, but they have a much lower impact on our circadian rhythm than light exposure and intake.
Our Circadian Rhythm
When light enters the eye, it is transmitted into the retina and turned into neural impulses that travel to the hypothalamus and to the suprachiasmatic nucleus (SCN). While the hypothalamus is the part of our brain that is responsible for a variety of core functions, the SCN is the master clock.
Light comes in via the Eye, then hits the SCN, which helps to trigger melatonin production
The SCN communicates with a variety of other neural centers that are responsible for sleep and wakefulness. The amount of light the SCN registers is what determines whether we are more or less likely to be awake or asleep, working through these other neural centers and a variety of other neural transmitters, including serotonin, acetylcholine, dopamine, and orexin.
Another important influence on the circadian rhythm – and directly related to light exposure – is melatonin.
The Chemical Structure of Melatonin
This hormone is commonly released in darkness, roughly 4-5 hours before we go to sleep, and suppressed by light, allowing us to both fall asleep and wake up. This effect is one of the reasons why it can be helpful in some people, both in shifting the circadian rhythms and in helping with sleep.
But to reiterate, the most important influence on our circadian rhythm is light; when you get light and how much light you get will be important in setting your circadian rhythm and therefore, influencing your ability to fall and stay asleep.
Related Questions:
- How does our circadian rhythm influence sleep?
- Does making your room completely dark help one to sleep better?
- Why exactly would morning light exposure help you fall asleep at night?
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