Autumnal Equinox: Water dry up

April 5th, 2012
by Jo Law

The Bureau of Meteorology’s announcement of the end of the 2011 – 12 La Niña event may signal: ‘water dry up’, but this pentad began with a tremendous downpour in Austinmer. Lightning flashed over the ocean and thunder roared as I read Hollis his bedtime stories. The thunder claps directly overhead sent the little boy clinging tightly onto me. Daylight saving ended that night, or more precisely in the early morning of Sunday April 1st, at 2am. ‘Turning back the clock’ holds the promise of a sleep-in. Although a small child in the household may prevent such an eventuality, there is always the consolation price of putting forward his bedtime.

Like weather, sleep is a frequently discussed topic that almost everyone has something to say about. When babies and young children come into the picture, there seems to be no way of getting away from talking or thinking about sleep. Sleepiness or the process of falling asleep is a complex biological process that involves at least 2 physiological mechanisms: first, the accumulation of the chemical, adenosine, in the basal forebrain during our wakeful hours; secondly, the secretion of the hormone, melatonin, from the pineal gland as night falls and light fades.

The first mechanism occurs when adenosine increases during our waking hours. An elevated levels of this chemical is what makes us sleepy. It has been shown that adenosine steadily decreases during sleep. The second mechanism is tied to the light/dark cycle. Melatonin is released when photoreceptors in our eyes sense no light (i.e. darkness). The circulation of melatonin in the body contributes to the drowsiness experienced before sleep. The light of daybreak sends signals to the brain and ‘resets’ our body clock, synchronizing our circadian rhythm to the Earth’s rotation. Artificial lighting provides a way to suppress the the production of melatonin while caffeine presents itself as a convenient blocker of adenosine. It seems that we try as hard to stay awake as we do to get more sleep.

So winding our clocks back provides a way for our bodies to adjust to the shortening daylengths. The accumulated adensosine breaks down during sleep. As the light of dawn sends signals to our pineal glands to cease the production of melatonin, we gradually rise to the surface of our consciousness from a night of sound sleep, hopefully.

This pentad ends on the day Hong Kong celebrated its Children’s day. Tonight, our child went to bed at a respectable hour of 8 o’clock.

2 Responses to “Autumnal Equinox: Water dry up”

  1. 1 Lucas
    April 5th, 2012 at 21:40

    nice diagram jo!

    i’m sure Mr Tufte would approve.

    Wish you still had that old system of comment on blog = postcard in the mail!

  2. 2 Jo Law
    April 9th, 2012 at 23:43

    Thanks, Lucas. The inspirational Mr Tufte has been behind all these maps and graphs.

    Sorry, no postcards but the posters should be something to look forward to.