For most sleep-deprived college students, coffee is a staple of their morning routine, especially with finals fast approaching. This bitter brew has the ability to make us feel at least a little more fresh, awake, and prepared for the day.
Researchers at Johns Hopkins University have been looking into the question of what makes coffee so effective. It contains caffeine, which is a stimulant, a psychoactive substance that temporarily increases alertness and energy. Caffeine acts directly on the central nervous system (CNS), and is able to bypass the blood–brain barrier, a defense that prevents viruses and unwanted molecules from entering the CNS. This allows caffeine to interact with neurotransmitters, the chemical messengers that transmit signals between neurons, by mimicking or altering their behavior.
Caffeine is thought to work by three main mechanisms. First of all, it can constrict cerebral blood vessels, preventing the production of the chemical adenosine. High levels of adenosine are associated with sleepiness, which is why we feel tired at the end of a long day: adenosine levels in our brains gradually increase throughout the day. This interference with adenosine receptors leads to effects on other neurotransmitters that are responsible for regulating our emotions and physical states. Secondly, caffeine also activates nonadrenaline neurons, increasing the transmission of the neurotransmitter dopamine, which has been shown to improve mood and attention. Thirdly, it increases the activity of acetylcholine and raises serotonin levels to help one feel more relaxed and energetic and also improve long-term memory.
Long story short, through a variety of biological mechanisms, caffeine convinces our brains to think that we have gotten more sleep than we really did. However, user be warned: prolonged use may lead to dependence. So think twice before you drink your fourth espresso of the day, college students!