Caffeine, Nicotine are alkaloids and act as central nervous system stimulant, weather consumed in food or as medicines. It alters the way your body functions and changes your behavioral pattern. Main effect of caffeine on the body is to increases temporary sense of wakefulness and alertness. It may also cause disturbed sleep, irregular heartbeats, high blood pressure, tremors, nervousness, dizziness, dependency if consumed in excess.
Caffeine is similar to Adenosine, an inhibitory neuro transmitter present in human cells. It binds with the adenosine receptors present in brain and acts as a depressant. When caffeine is consumed our nerve cells recognizes it binds with Adenosine receptors and provide an immediate jolt and eleminate drowsiness temporarily. since caffeine is CNS stimulant it causes the body toforget that it is tired. But the caveat is that tolerance is built quickly; to make up for adnenosine receptors that have been inhibited by caffiene, brain develpos more receptors as a result more caffeine is needed to prevent drowsiness. When brain detects increased levels of adenosine, it makes you feel more tired and drowsy and now you need even more caffeine to keep energy levels and helps your barin to functions at your best.
Caffeine immediately improves the mood by stimulating Dopamine, although it depletes Serotonin over time, which will ultimately cause you to feel even more drowsy and dull. Serotonin helps to regulate many bodily functions, including sleep cycles, carbohydrate cravings, pain control, digesation and etc. low levels of serotonin have also been linked with depressed immune functions.
The negative effects are linked to overconsumption of caffeine. it interferes with the sleep cycle. a person who takes caffeine on daily basis, no longer experiences the gud effects of it and feels more awake and unable to concentrate. The less caffeine you consume, the better it works. While body and brain receptors responds to caffeine as part of normal biology- more you use, your body gets more used to its signals, and stops responding in same way. There no desirable response. This is called Attenuation, same doses of caffeine has less effects.
Caffeine is considered under psychoactive substances producing dependence. If it is consumed in excess it produces physical dependence, psychic dependence and tolerance and withdrawal syndrome
The typical content of caffeine in commonly used drinks is as follows, tea - 45 mg/ cup, instant coffee- 60mg/ cup, brewed coffee- 100mg/cup, cola drinks 20-50 mg/can. caffeine is also present in chocolates. Excessive consumption of caffeine more than 250mg per day is called as caffienism, producing restlessness, nervousness, excitement, insomnia, flushed face, diuresis, muscle twitching, ramblings of thoughts and speech, irregular heartbeats, psychomotor agitation.