What is the body clock?

How do we know when to wake up without an alarm?
11 February 2020




What exactly is the body clock? Megan McGregor has been finding out...

Megan - How do we know when to wake up without an alarm? Why don’t we just keep sleeping? For that we have our body clock to thank. It's our body’s way of keeping track of time to coordinate vital functions like metabolism, when we eat and when we grow and repair our tissues.

The body clock is powered by a cluster of nerve cells called the supra-chiasmatic nucleus, or SCN. This rice grain sized structure sits in the brain's hypothalamus.

The SCN "ticks" like a genetic domino effect: a series of genes turn on and off in sequence, producing proteins that turn on the next gene and turn off the first one. The whole process takes about 24 hours to complete the genetic cycle.

The clock's time is updated by signals sent from the retina, which uses daylight to reset the system. This is how we adapt to jet lag.

The SCN transmits the time signal to the rest of the brain through connections to other nerve cells, and to the rest of the body by controlling the release of the hormone cortisol from the pituitary gland.

The cortisol signal is carried through the bloodstream to pass on the time signal to every cell in the body. This means that literally every one of our organs knows what time it is, and metabolism is efficiently synced up in all of them, helping us to perform at our best each day...


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