International A Level Biology / Cardiovascular health and risk
Risk factors for cardiovascular disease
Edexcel International A Level Biology (YBI11), chapter 3: Cardiovascular health and risk, specification point 1.12. Free lesson.
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Risk factors change the chance of developing cardiovascular disease (CVD), which affects the heart and blood vessels. Most raise risk by increasing blood pressure, damaging the artery lining or speeding up plaque formation.
How the risk factors feed one cycle
Atherosclerosis is the build-up of plaque in artery walls. The endothelium is the artery’s thin inner lining, and the lumen is the space blood flows through. High blood pressure can damage the endothelium. Inflammation then brings white blood cells and cholesterol into the artery wall, where plaque forms. Plaque narrows the lumen and makes the artery less elastic, so blood pressure rises further. This is positive feedback: each change makes the next one worse. When explaining a risk factor, link it to endothelial damage, plaque formation or raised blood pressure.
Which risk factors cannot be changed?
Three of the seven risk factors are fixed: genetics, age and gender. They cannot be changed, but knowing about them can make it more important to manage the other risk factors. Genetics: inherited alleles, or versions of genes, can lead to high blood pressure or high LDL cholesterol. Early heart disease in a parent is a warning sign. Age: plaque builds up and arteries stiffen over decades, so risk rises with age. Gender: middle-aged men have more CVD. Before the menopause, oestrogen is thought to protect women partly by raising HDL, a helpful cholesterol carrier. Women’s risk…
How diet affects blood pressure and plaque
Two nutrients to name are saturated fat and salt. They raise CVD risk in different ways, but both feed into the same cycle. A diet high in saturated fat raises LDL cholesterol. More cholesterol can then build up in damaged artery walls, so plaque forms faster. Too much salt lowers the blood’s water potential. More water is held in the blood, increasing blood volume and raising blood pressure. The higher pressure can damage the endothelium.
How smoking raises CVD risk
Two chemicals in cigarette smoke have important effects. Nicotine raises pressure and makes platelets stickier. Carbon monoxide reduces the oxygen carried in the blood. Other chemicals in smoke also damage the endothelium directly. Nicotine causes adrenaline release. The heart beats faster and the arteries constrict, or narrow. Blood pressure rises, which can damage the endothelium. Stickier platelets make a clot on a plaque more likely. Carbon monoxide binds tightly to haemoglobin, taking the sites that oxygen would use. With less oxygen carried, the heart beats faster. The heart…
How inactivity increases risk
Inactivity mainly raises risk through weight gain and blood pressure. Someone who does little exercise uses less energy each day. If they take in more energy than they use, the extra is stored as fat and they gain weight. Being overweight raises blood pressure, which can lead to endothelial damage and plaque. Regular exercise lowers resting blood pressure and raises HDL. Someone who is inactive misses both benefits.
Explain the mechanism, not just the factor
Naming a risk factor is not enough. The marks come from explaining how it raises risk and linking the mechanism to the artery. For example, nicotine raises blood pressure, which damages the endothelium, so plaque forms and narrows the coronary arteries. If several factors are present, link their effects. High blood pressure damages the endothelium, while saturated fat raises LDL cholesterol. The LDL can build up at the damaged sites, so plaque forms faster. The narrowed artery then raises blood pressure further.