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Psychology
Alcohol and the Brain
GABA Up, Glutamate Down
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Alcohol changes how neurons communicate, so its effects are not just about feeling relaxed or social. It slows reaction time, weakens judgment, disrupts memory, and reduces coordination by shifting the balance of chemical signals in the brain. These changes matter because they can affect driving, decision making, learning, relationships, and safety. The brain areas most affected include the prefrontal cortex, hippocampus, cerebellum, and reward pathways.
Key Facts
- Alcohol enhances GABA signaling, which increases inhibition and slows brain activity.
- Alcohol blocks glutamate signaling, especially at NMDA receptors, which reduces excitation and can impair learning and memory.
- BAC = grams of alcohol per 100 mL of blood, and higher BAC generally means stronger brain impairment.
- The prefrontal cortex supports planning, impulse control, and judgment, and alcohol reduces its ability to regulate behavior.
- The teen and young adult brain is still developing until about age 25, making it more vulnerable to alcohol related changes.
- Tolerance means the same amount of alcohol produces less effect over time, which can increase risk for dependence.
Vocabulary
- GABA
- GABA is the brain's main inhibitory neurotransmitter, meaning it reduces the activity of neurons.
- Glutamate
- Glutamate is the brain's main excitatory neurotransmitter, meaning it increases the activity of neurons.
- Prefrontal cortex
- The prefrontal cortex is the front part of the brain that helps with planning, judgment, impulse control, and decision making.
- Tolerance
- Tolerance is when repeated alcohol use makes the brain less responsive to the same amount of alcohol.
- Dependence
- Dependence is a state in which the brain and body adapt to alcohol and may function poorly or feel withdrawal symptoms without it.
Common Mistakes to Avoid
- Thinking alcohol is only a stimulant because it can make people feel energetic at first, which is wrong because alcohol mainly acts as a depressant that slows brain activity.
- Assuming tolerance means alcohol is less harmful, which is wrong because tolerance can lead people to drink more and increase the risk of dependence and brain damage.
- Believing impaired judgment begins only when someone looks drunk, which is wrong because decision making and reaction time can decline before obvious signs appear.
- Ignoring age as a risk factor, which is wrong because teen and young adult brains are still developing and may be more sensitive to alcohol's long term effects.
Practice Questions
- 1 A person's reaction time is 0.25 s when sober and increases to 0.40 s after drinking. By how many seconds did reaction time increase, and what is the percent increase?
- 2 A student drinks 5 standard drinks in 2 hours. If the body metabolizes about 1 standard drink per hour, about how many standard drinks remain unmetabolized at the end of the 2 hours?
- 3 Explain why alcohol can make a person feel relaxed while also making their judgment, memory, and coordination worse. Use GABA, glutamate, and at least one brain region in your answer.