Factors affecting human healthIB MYP Biology: Revision notes
Section 1
Communicable and non-communicable diseases
A communicable disease is caused by a pathogen (such as a virus or bacterium) and can spread from one person to another. Measles, cholera and tuberculosis are examples.
A non-communicable disease is not caused by a pathogen and cannot be passed on. Heart disease, type 2 diabetes and lung cancer are examples. They are often linked to lifestyle, such as diet, exercise, smoking and alcohol, and can also be affected by genes and the environment.
Section 2
Diet, exercise and obesity
A balanced diet has the right amounts of each nutrient. Eating more energy than you use leads to stored fat. Obesity means having so much body fat that health is harmed, and it is a risk factor for heart disease and type 2 diabetes.
Regular exercise uses energy and glucose in respiration, helps to control body mass, strengthens the heart and lowers blood pressure.
Section 3
Type 2 diabetes and heart disease
In type 2 diabetes, body cells stop responding properly to insulin, so blood glucose stays too high. It is linked to obesity and a lack of exercise, and can often be controlled with a healthier diet and exercise.
In coronary heart disease, fatty deposits build up inside the coronary arteries and narrow them. Less blood reaches the heart muscle, which can cause a heart attack. A diet high in fat, obesity, smoking and high blood pressure all raise the risk.
Do not mix up the two types of diabetes. In type 1 the pancreas does not make insulin. In type 2 the cells do not respond to it.
Section 4
Smoking
Tobacco smoke contains tar, nicotine and carbon monoxide.
- Tar damages the cilia and the lining of the airways, causing infections and a cough. It contains chemicals that cause lung cancer. Damage to the alveoli causes emphysema and breathlessness.
- Nicotine is addictive and raises heart rate and blood pressure.
- Carbon monoxide combines with haemoglobin, so the blood carries less oxygen and the heart works harder.
Smoking also damages artery walls, which raises the risk of heart disease.
Section 5
Alcohol and other drugs
A drug is a substance that changes how the body works.
Alcohol slows the nervous system, so reactions and judgement are worse and accidents are more likely. Heavy long-term drinking damages the liver (cirrhosis), the brain and the heart, and adds energy to the diet.
Other drugs, such as cannabis and heroin, affect the nervous system and can cause addiction, mental health problems and damage to organs. They also affect families and cost society money in health care and accidents.
Must Know
- Communicable diseases are caused by pathogens and spread; non-communicable diseases are not and do not
- Obesity and lack of exercise raise the risk of heart disease and type 2 diabetes
- Smoking: tar, nicotine and carbon monoxide damage the lungs and heart
- Alcohol damages the liver and nervous system
- Drugs can cause addiction
That's the notes covered.
Carry on to the next subtopic.
Exam questions on Factors affecting human health
- A health clinic in Cairo records the illnesses of its patients during one week. A group of children who attend the same nursery all have measles, which spread from one child to the others. Separately, several adults have coronary heart disease, and none of them caught it from another person.Describe two differences between communicable and non-communicable diseases.2 marks
- Sipho is 15 and lives in Johannesburg. He drinks several sugary drinks a day, often eats fried food, and spends most evenings sitting at a screen. His doctor measures his body mass and finds that he is well above the healthy range. The doctor warns him that he is at risk of serious illness later in life.Explain how regular exercise could reduce Sipho's risk of developing type 2 diabetes.2 marks
- A man in Jakarta is 52. He has smoked 20 cigarettes a day for 30 years. He is now breathless when he climbs stairs and he coughs every morning. His doctor tells him that tobacco smoke contains tar, nicotine and carbon monoxide, and that he is at risk of lung disease and coronary heart disease.Describe how tobacco smoke damages the gas exchange system.3 marks
Written by the Exaim team, led by Shaun Daswani (Head of Upper Secondary, Improve ME Institute; MSc Financial Mathematics, Imperial College London; BSc, UCL) and Jason Daswani (operational lead, Improve ME Institute; LSE).