Caffeine can block adenine nucleoside receptors in the brain. Adenine nucleoside can slow down the activity of nerve cells after binding with its receptor. Generally, the two are combined during sleep. Caffeine molecules are similar to adenine nucleoside and can bind to the same receptor.
However, it does not reduce cell activity, on the contrary, it prevents adenine nucleoside from binding to its receptor. Therefore, the activity of nerve cells increases, and nerve cells secrete adrenaline. Adrenaline makes the heart beat faster, blood pressure increases, muscle blood flow increases, blood flow in skin and viscera decreases, and the liver releases glucose to the blood.
In addition, caffeine, like aminopropylbenzene, can increase the neurotransmitter dopamine in the brain.
Unlike other substances that stimulate the central nervous system and alcohol, the effect of caffeine is quite short-lived. For most people, caffeine will not affect their attention and other advanced intellectual functions, so caffeinated drinks are often drunk in the workplace.
Drinking caffeine for a long time will lead to caffeine habituation in the body. If caffeine is stopped at this time, the body will be too sensitive to adenine nucleoside, and blood pressure will drop excessively, leading to headaches and other symptoms.
Too much caffeine can lead to caffeine poisoning. Its symptoms are irritability, nervousness, irritation, insomnia, blushing, polyuria and digestive tract discomfort. Some people will have these symptoms when they consume less than 250 mg a day. More than 1 g per day can cause spasms, sudden changes in thinking and language, unstable heartbeat, tachycardia and psychomotor agitation.
The symptoms of caffeine poisoning are somewhat similar to panic disorder and generalized anxiety disorder. 192 mg/kg, or for ordinary adults, 72 cups of coffee may cause half of the deaths.
There is no clear evidence that caffeine is related to bone loss and osteoporosis. In a study related to cola but excluding other carbonated drinks, it was found that caffeine was not the cause of bone loss. On the contrary, the content of phosphoric acid is directly related to osteoporosis in elderly women.