Beyond Sunlight: How Does Your Body Know What Time It is?

The body observes a lot more than most people think:

Zeitgebers

External stimuli such as light, food, noise, and temperature, known as Zeitgebers (timegivers), help synchronize internal rhythms with the environment, while morning light suppresses melatonin and influences hormones and brain activity involved in regulating sleep and wakefulness.

For this reason…

• rising body temperature around 10am (give or take latitude and daylight savings) increases energy and alertness, while
• afternoon changes can improve muscle activity and coordination, and
• bright screens at night can disrupt these signals and make sleep more difficult.

As for that brain activity:

• Interconnected brain systems track seconds, hours, and seasons, with the suprachiasmatic nucleus (SCN) in the hypothalamus acting as the primary circadian clock.
• CLK proteins accumulate during the day and activate genes involved in wakefulness and production of PER proteins, which eventually suppress CLK production; as PER levels fall, CLK rises again, helping drive the day-night cycle.

As for how it does this, one theory proposes that predictable communication times between neurons create recurring activity patterns that the cortex can use to estimate elapsed time.

So, much the same principle as many kinds of clock!

For more on all of this, enjoy:

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Want to learn more?

You might also like:

The Circadian Rhythm: Far More Than Most People Know

Take care!