Circadian rhythms are any physical, mental and behavioural changes
that follow a roughly 24-hour cycle, responding primarily to light and darkness
in an organism's environment. These rhythms are found in most living things. Circadian
rhythms are important in determining human sleep patterns.
How does the circadian rhythm come about?
Circadian rhythms are produced by natural factors within the body,
but however are also affected by the environment around us. Light is one of the
main things that influence these rhythms by turning genes which control an
organism's internal clocks, on or off.
Where is it located?
The primary circadian “clock” in mammals is located in the
hypothalamus, in the suprachiasmatic nucleus (SCN). The SCN controls the
production of melatonin, a hormone that makes you sleepy. It receives its
information through the eyes and so when there is less light, the SCN tells the
brain to release more melatonin to make you sleepy. If this suprachiasmatic
nucleus is destructed, it would result in an absence of a regular sleep-wake
rhythm.
How do circadian rhythms affect body function and health?
Circadian rhythms influence sleep-wake cycles, hormone release, body
temperature and other body functions.
Health problems can be caused by a disturbance of the circadian rhythm;
it has been linked to various sleeping disorders such as insomnia. They also
play a part in the reticular activating system, which is crucial for
maintaining a state of consciousness.
Even though obesity and diabetes are mostly associated with
lifestyle and genetic factors, a disturbance of the circadian rhythm can affect
metabolism. Chronic jet-lag and shift work (services available 24/7) are
examples of a disturbance of the circadian rhythm. These cause humans to eat
during their normal resting periods which can cause an increase in body mass
and insulin secretion and therefore lead to obesity and diabetes.
How does circadian rhythm research contribute
to human health?
Scientists have found that the time a drug is
given to a patient has an affect on the drug’s efficiency. Circadian rhythm
research can maximise the therapeutic effect of drugs such as chemotherapeutic
drugs (used for cancer treatment) on patients by targeting the times in which
the normal cells are less likely to be undergoing DNA synthesis. This is
effective because when cells are not undergoing synthesis, higher levels of
drugs can be tolerated. The circadian rhythm research can also lead to
treatment for sleep disorders. KHL
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