Alcohol Effects on the Body: Liver Damage, Reaction Time and Dependence
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Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Key concept
Alcohol is a depressant that slows nervous system activity, increases reaction time, impairs judgement and coordination, and with long-term use causes liver damage including cirrhosis.
Alcohol questions require more than a list of health effects. Extended answers must explain how alcohol acts as a depressant on the nervous system and connect this to impaired reaction time and judgement, then link long-term use to specific organ damage.
Alcohol as a depressant
Alcohol (ethanol) is a depressant. It slows the transmission of nerve impulses in the brain. This reduces inhibitions, impairs judgement and coordination, and increases reaction time. The person responds more slowly to stimuli, which is why drink-driving is extremely dangerous.
At higher doses, alcohol can cause slurred speech, blurred vision, loss of balance and unconsciousness. Very high blood alcohol levels can depress the breathing centre in the brain, leading to coma or death.
Short-term and long-term effects
Short-term effects
Long-term effects
Slower reaction time
Liver damage and cirrhosis
Impaired judgement and coordination
Brain damage and memory loss
Dehydration and nausea
Increased risk of heart disease
Lowered inhibitions
Alcohol dependence (addiction)
The liver breaks down alcohol using enzymes. Prolonged heavy drinking overwhelms the liver, leading to fatty liver, hepatitis and eventually cirrhosis, where liver tissue is replaced by scar tissue and the liver can no longer function properly.
Alcohol dependence
Regular heavy drinking can lead to tolerance (needing more alcohol for the same effect) and physical dependence. Withdrawal symptoms include tremors, anxiety, sweating and in severe cases seizures. Psychological dependence means the person feels unable to cope or relax without alcohol.
The social consequences parallel other addictive drugs: relationship breakdown, job loss, financial problems and increased risk of accidents. Exam answers should connect the depressant action on the nervous system to these broader consequences.
Try a focused question (3 marks)
Explain why a person who has consumed alcohol is more likely to have a car accident.
Show the answer and marking guidance
Alcohol is a depressant that slows nerve impulse transmission in the brain.
This increases reaction time so the driver responds more slowly to hazards.
Judgement and coordination are also impaired, making it harder to control the vehicle.
Original Cambridge-style practice written for this site. It is not an official Cambridge past-paper question.
Common mix-ups to avoid
Check these points against your own answer before moving on.
Calling alcohol a stimulant because it makes people feel confident.
Describing only liver damage without explaining the nervous system effects.
Writing that alcohol "kills brain cells" without mentioning slowed nerve impulse transmission.
Forgetting to name cirrhosis when discussing long-term liver damage.