2.7.4Inquiry Process
Coronary Heart Disease- Skills — IB Biology HL Revision Notes & Topical Questions
5 min read 5 parts Lesson 76 of 160
Curriculum Equation Key قوانين الرقم الهيدروجيني والاتزان الأيوني - pH & Acid-Base Equilibrium FormulasFast Exam Solution
pH = -log[H⁺] | pOH = -log[OH⁻] | pH + pOH = 14 | [H⁺][OH⁻] = 10⁻¹⁴
Word Equation & Conditions: الرقم الهيدروجيني = -لوغاريتم تركيز أيون الهيدروجين | pH + pOH = 14
Location & Specifications: الاتزان الأيوني، كيمياء 3 ثانوي، التحصيلي، و AP Chemistry.
Part 1 of 5How Coronary Heart Disease Develops
Coronary arteries supply the heart muscle itself with oxygenated blood.
1
Damage to the lining of a coronary artery, caused for example by high blood pressure or smoking, allows low-density lipoprotein and cholesterol to accumulate in the wall.
2
White blood cells enter and take up the lipids, forming fatty streaks, and fibrous tissue grows to produce a raised atheroma.
3
As the plaque grows, the lumen narrows and the artery becomes less elastic, a condition called atherosclerosis.
4
A rough plaque can break open, triggering platelets to form a blood clot, called a thrombus, at the site.
5
If the clot blocks the artery, heart muscle behind it is starved of oxygen and may die, which is a myocardial infarction or heart attack.
Part 2 of 5Risk Factors
Smoking
- Smoking Chemicals in tobacco smoke damage artery linings, raise blood pressure and make platelets stickier.
Diet high in saturated fat
- Diet high in saturated fat Raises blood cholesterol levels, which increases the amount of lipid deposited in artery walls.
High blood pressure
- High blood pressure Mechanical stress on the artery wall causes damage that begins plaque formation.
Inactivity and obesity
- Inactivity and obesity Lack of exercise and excess body fat are associated with higher blood pressure and unfavourable blood lipid levels.
Genetics, age and sex
- Genetics, age and sex Inherited factors, increasing age and being male are risk factors that cannot be changed.
Part 3 of 5Analysing Data
Analysing Data
Correlation
- Correlation A correlation shows that two variables change together, such as smoking and heart disease rates in a population.
Causation
- Causation Evidence for causation needs a plausible mechanism, a dose response and control of confounding variables.
Relative risk
- Relative risk Dividing the rate in an exposed group by the rate in an unexposed group shows how many times more likely disease is.
Study design
- Study design Large samples, matched groups and long follow-up periods make epidemiological studies more reliable.
| Group | Cases per 10 000 per year |
|---|---|
| Smokers | 150 |
| Non-smokers | 50 |
Part 4 of 5Worked Example
Question
- In a study, 150 per 10 000 smokers and 50 per 10 000 non-smokers develop coronary heart disease each year.
- Calculate the relative risk for smokers.
- Rate in exposed group = 150 per 10 000.
- Rate in unexposed group = 50 per 10 000.
- Relative risk = 150 ÷ 50 = 3.0.
Answer Smokers in this sample are three times as likely to develop coronary heart disease as non-smokers.
Part 5 of 5Exam Checklist & Tips
2.7.4 – Key Points for the Exam
- Atherosclerosis The build-up of fatty deposits and fibrous tissue in artery walls.
- Thrombus A blood clot that forms in a vessel.
- Myocardial infarction Death of heart muscle caused by loss of blood supply.
- Coronary artery An artery that supplies blood to the heart muscle.
- Correlation A statistical relationship between two variables that does not by itself prove cause.
Common Mistakes
- Writing that a correlation proves one factor causes the other.
- Mixing up the coronary arteries with the pulmonary artery or the aorta.
- Saying a heart attack is a failure of the heart's electrical system; it is caused by blocked blood supply.
- Confusing a thrombus (a clot in place) with atherosclerosis (plaque build-up).
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