One-minute lecture: What do summer days do with the brain?
With us in Estonia, the day is once too long, once too short. Tallinn University junior research fellow Mark Tamm, what happens with the brain when on Midsummer's Eve at 11 pm the sun still glows in the sky?
In summer, in addition to the weather, also our brain's working mode changes in Estonia.
The body's internal day-night rhythms are managed in the brain by a biological clock, whose main clock-turner is light. In the retina of the eye, special cells sensitive to short-wave or bluish light are found, which give the brain a sign when the day begins or ends.
At the day's ending, the pineal body located in the brain begins to secrete melatonin – the sleep hormone, which gives the body a sign that it is time to switch to night mode. In the Estonian summer, however, also the bright twilight gives the brain a sign that the day is not yet completely ended. Therefore, the melatonin level begins to rise later, sleepiness arrives later.
In everyday life, this means that the mind stays sharp longer in the evening, sleep time shifts later, and if the morning alarm clock rings also in summer at the same time, also sleep becomes less. So can long bright summer evenings make the being more alert regardless of that, that the body may not get enough time for recovery.