How Drugs Affect the Brain

Ayanna Smith

The human brain is the most complex organ in the body. You need it to drive a car, to enjoy a meal, to breathe, and to enjoy everyday activities. The brain regulates your body’s basic functions, and allows you to interpret and respond to everything you experience.

The brain is made up of many parts with interconnected circuits that work together as a team.  Networks of neurons send signals back and forth to each other and among different parts of the brain, spinal cord, etc. Drugs interfere with the way neurons send, receive, and process signals via neurotransmitters. Neurotransmitters are endogenous chemicals that enable neurotransmission. It is a type of chemical messenger which transmits signals across a chemical synapse, such as a neuromuscular junction, from one neuron  to another “target” neuron, muscle cell, or gland cell.

Drugs interfere with the way neurons send, receive, and process signals via neurotransmitters. Some drugs, such as marijuana and heroin, can activate neurons because their chemical structure mimics that of a natural neurotransmitter in the body. Other drugs, such as amphetamine or cocaine, can cause the neurons to release abnormally large amounts of natural neurotransmitters or prevent the normal recycling of these brain chemicals by interfering with transporters.

Drugs will alter brain areas that are necessary for vital functions and may drive the compulsive drug use that marks addiction. Brain areas affected by drug use include:

the Basal Ganglia, which play an important role in positive forms of motivation, including the pleasurable effects of healthy activities, the Extended Amygdala which plays a role in stressful feelings like anxiety, and the Prefrontal Cortex which powers the ability to think.

Just as drugs produce intense euphoria, they also produce much larger surges of dopamine, powerfully reinforcing the connection between consumption of the drug, the resulting pleasure, and all the external cues linked to the experience. Large surges of dopamine “teach” the brain to seek drugs at the expense of other, healthier goals and activities.

For the brain, the difference between normal rewards and drug rewards can be likened to the difference between someone whispering into your ear and someone shouting into a microphone. As a result, the person’s ability to experience pleasure from naturally rewarding activities is also reduced.