Caffeine (C8H10N4O2), known medically as
1,3,7-trimethylxanthine, is a legal stimulant and diuretic used by a large
percentage of the Earth's human inhabitants. It can be found naturally in
drinks like coffee and tea, and has been artificially introduced into soft
drinks like 'Coke' for example. Additionally, small amounts can be found in
solid foods like chocolate. The primary method of obtaining pure caffeine is
through the decaffeination of coffee and tea, and in this state caffeine
appears as a fine white powder. When ingested, this powder is very bitter.
The primary effect of caffeine on the human body, and the
one that it is most often consumed for, is that of cardiac stimulation -
caffeine gives the consumer an 'energy boost' that lasts for a period of time
proportional to the amount of caffeine ingested. Cardiac stimulation is
achieved indirectly through the release of epinephrine (adrenaline) by the
pituitary gland; however, in order to get the pituitary to release epinephrine,
caffeine must first cause an increase in nerve cell activity in the brain.
To do this, caffeine takes the place of adenosine, a
naturally occurring chemical in the body that slows down nerve cell activity
and dilates blood vessels to allow for the increased oxygen uptake necessary
during sleep. Caffeine binds to adenosine receptor sites on nerve cells in the
brain, and instead of slowing activity, it quickens the pace at which nerve
cells fire, warding off drowsiness. It does this by lowering the trigger level
for norepinephrine, increasing the likelihood that the firing of one nerve cell
in the brain will cause neighbouring cells to fire. This increased activity in
the brain alerts the pituitary gland, and it releases epinephrine, setting off
the 'fight-or-flight' response in the human. One of the functions of the
fight-or-flight response is to release sugar (stored in the liver in the form
of glycogen) for immediate use; this is the source of the energy used in the
'boost' provided by ingesting caffeine.
How Caffeine Becomes Addictive
In addition to touching off the fight-or-flight response,
caffeine also increases dopamine levels in the brain. Dopamine is a
neurotransmitter that activates the pleasure centre in the brain; by
manipulating the level of dopamine, caffeine artificially makes the consumer
feel good for a short period of time. This is the same mechanism used by both
cocaine and heroin.
As well as providing an immediate 'feel-good' sensation,
caffeine encourages long-term addiction by depriving the consumer of a good
night's sleep. Because adenosine reception is essential to deep sleep and it is
blocked by caffeine, consumers wake up feeling irritable, and use caffeine to
mentally 'awaken' themselves so that they can function 'properly' - as though
they had had a good night's sleep. In this way, a positive feedback loop is
created, and consumers cannot abstain from caffeine consumption without adverse
effects.
Positive Uses of Caffeine
Caffeine can be used in treatment of acute asthma - because
of the overall vasodilation effect caffeine has on the human body, the airways
in the lungs are also widened slightly (this effect is known specifically as
bronchodilation), enabling someone afflicted with asthma to breathe more
easily. While there are more asthma-specific drugs on the market, caffeine will
do if there's nothing else around.
Another use of the vasodilation effect of caffeine can be
found in headache relief; constriction of blood vessels in the brain can cause
major headache pain, and caffeine relieves this pain by widening the blood
vessels. For this reason, caffeine can be found in many specialised headache
medicines.
Additionally, caffeine can be used to treat ADHD, a
hyperactivity disorder. People with ADHD have a lowered ability to focus and a
shortened attention span, and stimulants like caffeine (and Ritalin, the most
frequently-used treatment for ADHD) allow for longer periods of intense
concentration. Unfortunately, the side effects of caffeine make it impractical
as a long term solution to most medical conditions.
While caffeine causes negative results when used in the long
term, it is - like most things - safe in small amounts.
No comments:
Post a Comment