Caffeine crystals photomicrograph, viewed by polarized light

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Inside the body caffeine acts through several mechanisms, but its most important effect is to counteract a substance called adenosine that naturally circulates at high levels throughout the body, and especially in the nervous system. In the brain, adenosine plays a generally protective role, part of which is to reduce neural activity levels – for example, there is some evidence that adenosine helps to induce torpor in animals that seasonally hibernate. Adenosine acts as an inhibitor neurotransmitter that suppresses activity in the central nervous system. Consumption of caffeine antagonizes adenosine and increases activity in neurotransmission including acetylcholine, epinephrine, dopamine, serotonin, norepinephrine and glutamate. There has also been conclusive evidence that caffeine inhibits acetylcholinesterase, an enzyme that breaks down acetylcholine; therefore the duration of acetylcholine is increased in the nicotinic and muscarinic receptors in the central nervous system.

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Photo credit: © Scenics & Science / Alamy / Afripics
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Keywords: adenosine, bull, caffeine, chemistry, coffee, crystals, filter, health, light, microscope, photomicrograph, polarized, red, tea, viewed