(funky music)
- Much like your computer and your microwave
or your standard model clock tower
your body comes equipped with a time keeping device.
Several actually.
The most prominent of these time keeping devices
are the circadian rhythms.
Daily cycles that run through roughly 24 hour periods
and effect things like hormone production,
body temperature, and of course sleep and wake.
Here are five surprising things
you might not have realized
about the clocks in your body.
There are many clocks operating at the same time
distributed all throughout your cells
but they're all controlled and synchronized
by a single master clock inside the brain.
This master clock is a group
of about 20,000 neurons called
the suprachiasmatic nucleus, or SCN,
which lives inside the hypothalamus.
Sort of in the center of your head
right above the optic nerve.
And this organ is important.
If you suffer damage to your SCN
it can cause all kinds of problems
for your natural circadian rhythms
such as the timing of sleep and wake.
When did organisms on Earth
first evolve internal clocks like circadian rhythms?
Many scientists think the biological clocks
first showed up more than 3 billion years ago
to track the day night cycle
in an organism called siana bacteria,
a single celled ocean dwelling creature
that still exists today.
We know it as blue green algae.
But why would some bits of floating ocean slime
need to know the time of day?
It's not they have to get up and go to work.
This actually isn't a totally settled question.
One interesting hypothesis is siana bacteria
involved circadian rhythms to create time
for two separate energy production jobs:
photosynthesis and nitrogen fixation
that would interfere with one another
if they happened simultaneously.
So we got photosynthesis during the day
and nitrogen fixation at night.
You know around two o'clock
when you've just had a nice fried ice-cream
calzone for lunch and you're trying to get through
those spreadsheets and suddenly you just hit
a great wall of sleepiness?
You're not alone.
In fact the early afternoon napping urge
is extremely common.
Circadian rhythms don't always fit our work schedules
because of another internal clock
known as sleep wake homeostasis
which is basically our body's way of saying
OK I realize you've been awake for a while now.
It's normal for an adult human to feel a little drowsy
after being awake for seven or eight hours.
In fact according to the national sleep foundation
the most common time for drowsiness in adults
are between two and four in the morning
and between one and three in the afternoon.
Our natural circadian rhythms operate
roughly on a 24 hour cycle
but they're not above being corrected
and are highly influenced by our surroundings.
Especially light and dark.
Simply put our bodies want to wake up
when the sun's up and go to sleep
when it's dark.
But in electrified societies light and dark
aren't always so predictable.
Artificial light whether that's a lamp in the living room
or a tablet screen in front of your eyes in bed
can trick our internal rhythms into thinking
it's time to be wide awake
and be watching YouTube videos in the middle of the night.
If you ever wanna become acutely aware
of the importance of your own body clocks
just try traveling to a far off longitude
and doing everything you would normally do
at the local time of day.
Not so easy, huh?
This effect commonly known as jet lag
happens when you're circadian rhythms
aren't correctly synchronized
with your new time zone.
Your brain is trained to release melatonin,
a hormone which induces sleep,
at the wrong time of day.
It can be a traveler's nightmare for a day or two.
Fortunately the body can usually adapt
just fine to the new time zone
and after a little bit of practice
and a few cycles of light and darkness
to re time the melatonin release schedule.
On the other hand the body might not adapt
nearly as well to daylight savings time
since no one ever bothers to let the sun and Earth
know we've moved seven am ahead an hour.
What's your favorite fact about biological clocks
and what do you do to make sure
yours run on time?
Let us know in the comments
and if you like this video
click on the thumbs up button
and subscribe to our channel for more.
And if you wanna learn more about body clocks
and circadian rhythms
check out ten weird facts about biological rhythms
at howstuffworks.com.
You'll be right now time. (laughs)
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