A drug is any substance that affects how your body works. This includes medicines (helpful drugs), alcohol, tobacco, caffeine, and illegal drugs. All drugs carry risks and must be used responsibly.
Check: What is a drug?
Flowchart
Use the pathway to build a clear mental model. Open each node and answer the check question.
1) Understand what drugs are
2) Learn about tobacco and the circulatory system
Smoking damages the heart and blood vessels. Nicotine increases heart rate and blood pressure. Tar coats the lungs and contains carcinogens. Carbon monoxide reduces oxygen-carrying capacity of blood.
Check: How does carbon monoxide in cigarette smoke affect blood?
3) Learn about alcohol and the circulatory system
Alcohol is a depressant - it slows down brain and body functions. Long-term heavy drinking can weaken the heart muscle and raise blood pressure, increasing risk of heart disease.
Check: Why is alcohol called a depressant?
4) Understand medicinal drugs
Medicines are drugs used to treat illness. They must be used correctly - right dose, right person, with adult supervision. Even helpful medicines can be harmful if misused.
Check: Why is it important to use medicines correctly?
Explanation
What is a Drug?
A drug is any substance that changes how your body works. Some drugs are helpful (medicines), but others can be harmful. It's important to understand how drugs affect the body, especially the circulatory system.
Tobacco and the Circulatory System
Cigarette smoke contains thousands of chemicals, including:
- Nicotine - highly addictive; increases heart rate and blood pressure; makes blood vessels narrower
- Carbon monoxide - binds to haemoglobin in red blood cells, reducing how much oxygen they can carry
- Tar - sticky substance containing carcinogens (cancer-causing chemicals); damages lungs
Smoking significantly increases the risk of heart disease, stroke, and lung cancer. The good news: quitting smoking reduces these risks.
Alcohol and the Circulatory System
Alcohol is a depressant - it slows down the nervous system. Effects include:
- Immediate effects - slowed reactions, impaired judgment, loss of coordination
- On the heart - can cause irregular heartbeat; long-term heavy drinking weakens heart muscle
- On blood pressure - raises blood pressure over time
- Addiction - regular drinking can lead to physical dependence
Caffeine
Caffeine (in coffee, tea, cola, energy drinks) is a stimulant - it speeds up the nervous system. It increases heart rate and can cause difficulty sleeping. Energy drinks often contain high levels and are not recommended for children.
Medicinal Drugs
Medicines help treat illnesses when used correctly:
- Painkillers (paracetamol, ibuprofen) - reduce pain and fever
- Antibiotics - kill bacteria (don't work on viruses)
- Asthma inhalers - help open airways
Even helpful medicines can be dangerous if taken incorrectly. Always follow dosage instructions and only take medicine given to you by a parent/carer or doctor.
Key Vocabulary
- Drug: Any substance that changes how the body works.
- Depressant: A drug that slows down the nervous system (e.g., alcohol).
- Stimulant: A drug that speeds up the nervous system (e.g., caffeine).
- Carcinogen: A substance that can cause cancer.
- Addiction: When someone cannot stop taking a drug despite harmful effects.
Why does this matter?
Understanding how drugs affect the body helps you make informed decisions about your health. Tobacco and alcohol are the two most harmful legal drugs in the UK, causing thousands of deaths each year. Learning about their effects now helps protect your health throughout life.
Examples
Example 1: Smoking Ban Success
In 2007, the UK banned smoking in enclosed public spaces (pubs, restaurants, workplaces). Within a year, hospital admissions for heart attacks dropped by 2.4%. This showed how quickly reducing exposure to cigarette smoke improves heart health. The ban also helped many smokers quit.
Example 2: Warning Labels
Cigarette packets in the UK must carry graphic health warnings showing diseased organs and warnings like "Smoking kills." This is because research shows people underestimate the harm of smoking. The warnings help people understand the real risks to their heart, lungs, and blood vessels.
Example 3: Athletes and Alcohol
Professional footballers and athletes often avoid alcohol during the season. Alcohol interferes with recovery, affects coordination, and can weaken the heart over time. Many sports teams have strict rules about drinking. This shows how seriously top athletes take the effects of alcohol on performance and health.
Example 4: Medicine Safety
Paracetamol is a common painkiller found in many homes. At the correct dose, it's safe and effective. But taking too much can cause serious liver damage - even death. That's why medicines have child-proof caps and clear dosage instructions. Always ask an adult before taking any medicine.
Practice
Answer all questions, then check your answers. Your quiz result is saved on this device.
Common Mistakes
Mistake 1: Thinking "drugs" only means illegal substances
In science, a drug is ANY substance that affects how the body works. This includes medicines, caffeine, alcohol, and tobacco - not just illegal drugs. Make sure you use the scientific definition.
Mistake 2: Confusing stimulants and depressants
Stimulants speed up the nervous system (caffeine, nicotine). Depressants slow it down (alcohol). Nicotine in tobacco is a stimulant - it increases heart rate - even though smoking damages health overall.
Mistake 3: Forgetting carbon monoxide's effect
Students often remember tar and nicotine but forget carbon monoxide. This poisonous gas binds to haemoglobin more strongly than oxygen, reducing the blood's oxygen-carrying capacity. This puts strain on the heart.
Mistake 4: Thinking medicines are always safe
Medicines are drugs too, and can be harmful if misused. Taking too much, taking someone else's prescription, or mixing certain medicines can be dangerous. Always follow instructions and ask an adult.
Summary
- Drug = any substance that changes how the body works (medicines, alcohol, tobacco, caffeine)
- Tobacco: nicotine (increases heart rate), carbon monoxide (reduces oxygen in blood), tar (damages lungs)
- Alcohol: depressant (slows nervous system); long-term can weaken heart and raise blood pressure
- Caffeine: stimulant (speeds up nervous system); increases heart rate
- Medicines: helpful when used correctly, but dangerous if misused
- Both tobacco and alcohol significantly increase risk of heart disease
Skills Checklist
- I can define what a drug is.
- I can explain how smoking affects the circulatory system.
- I can explain how alcohol affects the body.
- I can distinguish between stimulants and depressants.
- I can explain why medicines must be used correctly.