How does caffeine and ethanol affect the heart rate?

... How does caffeine and ethanol affect the heart rate? Introduction At rest a normal adult heart beats around 75 times per minute. During strenuous exercise it may rise to 200 beats per minute. The SAN (sino-atrial node) controls the heart rate. Information is sent via two autonomic nerves that link the SAN with cardiovascular centre in the medulla of the brain, the rate increases or decreases depending on the information received. Factors, which affect the heart:> The secretion of adrenaline. This may be under stress, excitement or other emotions.> Movement of the limbs (exercise). Heart rate and breathing rate increase due to oxygen levels falling and levels of carbon dioxide rising.> Blood pressure. When blood pressure is too high, a mechanism prevents increase in heart rate. Adrenaline is a hormone, which is produced by the adrenal gland; it is usually secreted in tiny amounts, when stressed or scared. It raises

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