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Tips for living well: taking time out
continued from page 1
We have drift-off
Let's wind back your life to yesterday evening. As the day drew to a close, you were probably unwinding as you watched late-night TV or made the best of that last glass of wine, but it was a different story inside your body. Your SCN had registered that daylight levels had fallen and sent a message to a tiny cone-shaped structure in your brain called the pineal gland. In response, it began pumping out a special sleepiness hormone called melatonin into your bloodstream. As your melatonin levels rose (which normally happens about two hours before bedtime), you started to feel drowsy, your core body temperature dropped and you began to feel ready for sleep.
Once under the covers, most of us take around 20 minutes to drop off and then every 90 minutes or so your brain cycles through five distinct sleep stages. The first two stages are fairly light and you can be woken easily if disturbed. Then, as the electrical activity in your brain is progressively dampened down, complete relaxation takes over and you enter the deeper third and fourth stages. Finally you reach the fifth stage - REM (rapid eye movement) sleep - which occupies a quarter of the night. Your eyes will dart madly back and forth under your eyelids as your brain goes full-tilt into electrical overdrive and begins experiencing highly emotional dreams.
Meanwhile back to last night - deep in your veins, that soporific hormone melatonin probably peaked between around 2 and 4 a.m., insuring that your distinct sleep cycles continued through the night. But while you were hopefully happily exploring the land of nod, there wasn't much rest for your master timekeeper, the SCN. As this morning broke and the light began to rise, it had to be on call to send a wake-up message to another gland in your brain, called the pituitary. The pituitary gland is part of a complex brain circuit (called the HPA or hypothalamic-pituitary-adrenal axis). A cascade of chemicals gets produced along this path, which ends just above your kidneys at the adrenal glands. Here, adrenaline and cortisol get pumped out - chemicals that raise your heart rate and blood pressure, make you feel alert and help release energy. So, as your cortisol level rose with this morning's light, it put paid to the sleepy effects of last night's melatonin and your brain began to wake up. And just to help you along the way, the pituitary gland did its morning chore as your very own in-built alarm clock - within 30 minutes of first waking, it had triggered a cortisol boost of a massive 100 per cent to ensure you didn't doze off again (in theory, that is, if the well-worn snooze button on most alarm clocks is anything to go by).
We have drift-off
Let's wind back your life to yesterday evening. As the day drew to a close, you were probably unwinding as you watched late-night TV or made the best of that last glass of wine, but it was a different story inside your body. Your SCN had registered that daylight levels had fallen and sent a message to a tiny cone-shaped structure in your brain called the pineal gland. In response, it began pumping out a special sleepiness hormone called melatonin into your bloodstream. As your melatonin levels rose (which normally happens about two hours before bedtime), you started to feel drowsy, your core body temperature dropped and you began to feel ready for sleep.
Once under the covers, most of us take around 20 minutes to drop off and then every 90 minutes or so your brain cycles through five distinct sleep stages. The first two stages are fairly light and you can be woken easily if disturbed. Then, as the electrical activity in your brain is progressively dampened down, complete relaxation takes over and you enter the deeper third and fourth stages. Finally you reach the fifth stage - REM (rapid eye movement) sleep - which occupies a quarter of the night. Your eyes will dart madly back and forth under your eyelids as your brain goes full-tilt into electrical overdrive and begins experiencing highly emotional dreams.
Meanwhile back to last night - deep in your veins, that soporific hormone melatonin probably peaked between around 2 and 4 a.m., insuring that your distinct sleep cycles continued through the night. But while you were hopefully happily exploring the land of nod, there wasn't much rest for your master timekeeper, the SCN. As this morning broke and the light began to rise, it had to be on call to send a wake-up message to another gland in your brain, called the pituitary. The pituitary gland is part of a complex brain circuit (called the HPA or hypothalamic-pituitary-adrenal axis). A cascade of chemicals gets produced along this path, which ends just above your kidneys at the adrenal glands. Here, adrenaline and cortisol get pumped out - chemicals that raise your heart rate and blood pressure, make you feel alert and help release energy. So, as your cortisol level rose with this morning's light, it put paid to the sleepy effects of last night's melatonin and your brain began to wake up. And just to help you along the way, the pituitary gland did its morning chore as your very own in-built alarm clock - within 30 minutes of first waking, it had triggered a cortisol boost of a massive 100 per cent to ensure you didn't doze off again (in theory, that is, if the well-worn snooze button on most alarm clocks is anything to go by).
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