How Does Caffeine Work in the Brain?

by Chris Dinesen Rogers

As you enjoy the effects of caffeine with your morning coffee, you may wonder how it influences brain function. This naturally occurring chemical initiates several processes not only in the brain but also in the cardiovascular and respiratory systems. These additional effects play a role in brain function. Within 15 to 45 minutes of consumption of a caffeinated beverage, your brain will begin to feel the results.

Epinephrine Release

Caffeine directly affects the brain through the release of the hormone epinephrine, also known as adrenaline. This is part of the reason your feelings of being sleepy will abate. Epinephrine puts your body in action mode by stimulating nervous system activity. This causes you to be more alert. A study done at Leeds Metropolitan University, published in the August 2011 issue of “Appetite,” explains that caffeine ingestion can increase positive feelings like those associated with prolonged exercise, demonstrating caffeine's effects on your mood.

Blood Vessels

The blood vessels in the brain also respond to caffeine. Normally, when you become tired, your body readies you for sleep through a complex series of reactions that ultimately cause the blood vessels in your brain to dilate. Caffeine has the opposite effect. Rather than dilate, the blood vessels constrict. This increases blood flow in the brain. Other effects in different parts of the body have an impact on blood vessel constriction and its results.

Oxygen Flow

During exercise, your body adapts to your needs for increased oxygen through various effects on the cardiovascular system. Caffeine mimics some of these effects on a smaller scale due to the release of epinephrine. Breathing and heart rate increase to deliver oxygen more quickly to the cells. Your brain perceives an increase in available oxygen because of the increased oxygen intake and elevated heart rate.


Caffeine affects people differently. Some may experience negative effects such as dizziness or headache. The feelings of alertness could translate into insomnia. However, if your body is used to caffeine, you may experience negative feelings as well if you stop consuming it suddenly. These symptoms will affect brain function. You may feel fatigued or experience headaches. Some individuals may feel moody or anxious. The more caffeine you consume, the more likely you are to experience these symptoms.

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This article reflects the views of the writer and does not necessarily reflect the views of Jillian Michaels or