Scientific studies reveal an internal clock in our brains that counts time and then “orders” various biological changes to occur throughout the day. For example, at night, our brain’s internal clock lowers our body temperature about 2°F and slows down our heart rate, while increasing tissue-repair and energy storage activities.
In some of us, this body temperature drops early in the evening and rises again around 6 a.m., whereas in others it stays high longer and doesn’t significantly rise again until 8-9 a.m. Similarly, our body’s release of the hormone melatonin, which is critical for our feelings of sleepiness, starts later in the evening—and lasts later into the morning—in some people than others. The increasing temperature and dropping melatonin levels we experience in the morning are what makes us wake up and feel alert. Those whose body temperature increases and melatonin drops early in the morning are “larks,” and those who shift later are “owls”. Amazingly, neuroscientists have uncovered the exact molecular basis for this difference, and it all revolves around how accurately our "brain-clocks" count time. Just like some people are tall and some are short, some people’s clocks run faster and some slower.
Why does all this matter for teenagers and getting up for school?