Drugs, alcohol and smoking

A drug is any substance that changes the way the body works. Medicines are drugs that treat illness. Other drugs, such as caffeine, nicotine and alcohol, are taken for how they make people feel, and they can harm the body, especially when used often.

Key facts

  • Medicines (paracetamol, antibiotics, insulin) treat illness or ease symptoms. Take them only as the label or a doctor says.
  • Recreational drugs: some are legal (caffeine; alcohol and tobacco for adults) and others are illegal (cannabis, cocaine, heroin).
  • Stimulants speed up the nervous system (caffeine, nicotine, cocaine); depressants slow it down (alcohol, solvents, heroin).
  • Many drugs are addictive: people feel they cannot manage without them and get withdrawal symptoms if they stop.
  • Cigarette smoke: tar coats the lungs, damages the cilia and can cause lung cancer; carbon monoxide reduces the oxygen the blood carries; nicotine is addictive and raises the heart rate.
  • Alcohol slows reactions and affects judgement; over many years heavy drinking damages the liver and brain. Smoking and alcohol in pregnancy harm the baby.

Worked examples

Example 1

Name the three harmful substances in cigarette smoke and say what each one does.

  1. Tar is a sticky black substance. It coats the lungs, damages the cilia that keep them clean, and can cause lung cancer.
  2. Carbon monoxide is a poisonous gas. It joins onto red blood cells, so they carry less oxygen.
  3. Nicotine is the addictive drug. It makes the heart beat faster and raises blood pressure.

Answer: tar damages the lungs and can cause cancer; carbon monoxide means the blood carries less oxygen; nicotine is addictive and makes the heart beat faster

Example 2

A student’s reaction times were 0.26 s, 0.25 s and 0.27 s, and then 0.22 s, 0.21 s and 0.23 s after a drink with caffeine. Find each mean and say what caffeine does.

  1. Before: (0.26 + 0.25 + 0.27) ÷ 3 = 0.26 s
  2. After: (0.22 + 0.21 + 0.23) ÷ 3 = 0.22 s
  3. The reaction time went down, so reactions were faster: caffeine is a stimulant.

Answer: before 0.26 s, after 0.22 s: caffeine is a stimulant, so reactions got faster

Example 3

Is each drug a stimulant or a depressant: caffeine, alcohol, nicotine?

  1. Stimulants speed up the nervous system: caffeine (in coffee, tea and cola) and nicotine (in tobacco).
  2. Depressants slow it down: alcohol slows reactions and makes people drowsy.

Answer: caffeine: stimulant; alcohol: depressant; nicotine: stimulant

Example 4

Why do smokers get out of breath more easily?

  1. Carbon monoxide takes the place of oxygen in red blood cells, so less oxygen reaches the muscles.
  2. Tar damages the alveoli (air sacs), so less oxygen gets into the blood, and it damages the cilia, so mucus builds up.
  3. Together these make smokers breathless sooner.

Answer: carbon monoxide means the blood carries less oxygen, and tar damages the air sacs and cilia in the lungs