Tick-tock goes our clock
Monday mornings don’t have to be grueling. After daylight savings time set our clocks back an hour over the weekend, getting out of bed in the morning may be easier, but that feeling won’t last. Your body needs time to adapt to the changed hours because it runs on its own biological clock.
This inner clock regulates our sleep-wakefulness cycle, our body temperature, and the amount of hormones in our blood at any given time.
Many organisms, including humans, have evolved to expect the 24-hour rotation of our planet. Diurnal species such as ourselves, active during the day, are cued by sunlight to be awake or asleep around the same time every day.
Our clock is regulated by a small area of the brain, the superchiasmatic nuclei (SCN). This group of about 10,000 cells receives signals from the retina, where sunlight is detected, and the regular variation of light “sets” the clock.
Interestingly, while the input of sunlight is important in “setting” the clock, the SCN is able to keep its own activity pattern even in the absence of sunlight, but the pattern strays closer to a 25-hour cycle, like a faulty clock when it is not “set” for too long.
The effect of the biological clock is obvious when you travel to another time zone: you still get tired at your regular bedtime, regardless of the time of day. The inner clock can be reset to new daylight hours by about one to two hours a day, so jetlag eventually wears off.
Less extreme than jetlag is the one-hour time change we experience twice a year when daylight savings starts or ends. This is why it was so easy to get up this past Monday: your body clock was slightly ahead for one day. Time, however, always has a way of catching up with you.
