FERNWOOD FITNESS - PULSE eMagazine - Issue#10 - Flipbook - Page 57
WHERE IS THE CLOCK?
HOW DOES IT WORK?
Scien琀椀sts have known for a
long 琀椀me that daily rhythms
are driven by some kind
of clock in our bodies. But
they didn’t work out exactly
where it was un琀椀l the middle
of the 20th century. They
found this out when they
did surgery on hamsters.
They took out a 琀椀ny part
of the brain of hamsters
called the suprachiasma琀椀c
nucleus (SCN). A昀琀er this, the
hamsters totally lost their
rhythm – and not just on
the hamster wheel. It used
to be easy to predict when
the hamsters would run on a
wheel. But a昀琀er they lost the
SCN, they ran at any and all
琀椀mes of the day and night.
That was the 昀椀rst big step
in understanding.
How the rhythms are
produced is complex. But we
can sum things up as follows:
special clock genes in the
SCN switch on which cause
proteins to be made. As these
proteins accumulate, along
with other chemicals, they
switch o昀昀 the clock genes.
The level of proteins then drop
to point where the genes are
able to switch on again and
the cycle restarts. This cycle of
switching o昀昀 and on happens
about once every 24 hours.
The SCN sends out signals to
the rest of the body that vary
according to this cycle. The
cycle is not just determined by
the SCN itself: it responds and
adapts to signals from outside
the body (principally light and
dark) to keep the organism
synchronised with the world
around it – that is, 琀椀cking at
the right 琀椀me.
IS LIGHT IMPORTANT
TO HOW THE BODY
CLOCK WORKS?
The most important external
signal for the biological clock
is light. When the eye senses
light, it sends signals to the
SCN. This resets the clock
every day. Our body does
this to make sure rhythms
don’t dri昀琀 out of line with the
environment. Although our
