Caffeine effects on heart rate, reaction time, and concentration
The health effects of caffeine have been extensively studied. Short term side effects such as headache, nausea, and anxiety have been shown as symptoms of mild caffeine consumption. The long term consequences of moderate caffeine consumption can lead to a reduced risk of developing Parkinson's disease, type 2 diabetes, hepatic diseases, and cardiovascular disease. Caffeine competitively inhibits different adenosine receptors and its associated G protein to make a person feel alert, it injects adrenaline into the system to give them a boost, and it manipulates dopamine production to make them feel good. A mild stimulant of the central nervous system, caffeine also stimulates cardiac muscle, relaxes smooth muscle, increases gastric secretions, and produces diuresis.
Caffeine increases heart rate by increasing stress hormone secretions. It has been shown there is an increase in brachial diastolic blood pressure, but not in brachial systolic blood pressure. However, both aortic systolic and diastolic blood pressures increase significantly during caffeine consumption. It has been noted that long term consumption leads to increasing aortic systolic pressure which leads to chronic arterial stiffness. The results of increasing blood pressure mostly contributes to blockage of Adenosine A1 and A2 receptors. Since caffeine blocks adenosine A2 receptors which has vasodilatory function, blood vessels become less dilated.(ie. vasoconstriction) However, it is controversial whether caffeine consumption increases heart rate. Some research shows that caffeine has no influence on heart rate. It is hard to say how much dosage will cause increasing heart rate as no studies have shown significant data. Different people have different tolerance for caffeine based on individual metabolic activity, so there is no clear distiction between caffeine consumption and the amount heart rate increases.
Many people drink coffee for its ability to increase short term recall. Likewise, in tests of simple reaction time, choice reaction time, incidental verbal memory, and visuospatial reasoning, participants who regularly drank coffee were found to perform better on all tests, with a positive relationship between test scores and the amount of coffee regularly drunk. Elderly participants were found to have the largest effect associated with regular coffee drinking. Another study found that women over the age of 80 performed significantly better on cognitive tests if they had regularly drunk coffee over their lifetimes.
Coffee and caffeine are associated with attention, concentration, learning, and memory but there is no conclusive evidence yet that caffeine has any effect on memory and cognitive function.
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