Page 13 - BBC Knowledge - October 2017 IN

W H A T H APPEN S I N MY BO D Y

...WHEN I SLEEP?
Sleep consists of two radically different physiological states. There is rapid eye movement sleep (REM) and non-rapid eye movement sleep
(NREM). The sleep stages seem to have different functions, but why we sleep is still not completely understood. Babies spend half of their
sleep in REM, but this drops to a quarter by the age of two. It is therefore thought that REM sleep is particularly vital for the developing brain.
In NREM sleep, brain activity slows and a person woken at this stage may feel groggy.

1. Pituitary gland 2. Mouth 3. Lungs
During non-REM sleep, the pituitary gland You produce less saliva, which reduces The throat muscles relax so your airway
produces growth hormone and secretes the need to swallow. Five per cent of adults narrows when inhaling. This can cause
prolactin. This counteracts dopamine, to also grind their teeth at night, mostly during snoring, or temporarily halt your breathing
lower general arousal levels. the early stages of sleep. for a few seconds (sleep apnoea).

4. Heart 5. Limbs 6. Bladder
Your pulse drops by 10-30bpm while The extra blood swells your arms and legs Vasopressin hormone levels rise. This
you sleep, lowering your blood pressure. slightly. Muscles are paralysed while reduces the amount of urine collected in the
Less blood flows to the brain, and more dreaming, but, between dreams, you change bladder to between a half and a third of
is diverted to your muscles. sleeping position 35 times a night. normal daytime levels.

WHY DO CHAMPAGNE
BUBBLES RISE FROM
THE BOTTOM OF A GLASS?
The bubbles are filled with carbon dioxide (CO2),
a gas 800 times less dense than the surrounding liquid.
Molecules of this gas accumulate in imperfections in
the glass and start to form a bubble, whose low density
supplies enough buoyancy to break off and float towards
the surface. In the process, they run into more molecules,
making the bubble even bigger and more buoyant, If your champagne glasses
are grubby, bubbles will form
and accelerating its ascent. RM
on the specks of dirt, betraying
your shoddy washing-up skills
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OCTOBER 2017