Higher Human Biology

1. Higher Human Biology Unit 2 Physiology & Health KEY AREA 7: Pathology of Cardiovascular Disease (CVD)

2. Higher Human Biology We are going to build on the knowledge and skills that you developed during N5 and will learn about the following Physiology & Health key areas : - Key Area 1 – Reproductive Organs Key Area 2 –Hormonal Control of Reproduction Key Area 3 – Biology of Controlling Fertility Key Area 4 – Ante- and Postnatal Screening Key Area 5 – Structure and Function of Arteries, Capillaries and Veins Key Area 6 – Structure and Function of the heart Key Area 7 – Pathology of Cardiovascular Disease (CVD) Key Area 8 – Blood Glucose Levels and Obesity

3. Physiology & Health Learning Intentions KEY AREA 7– Pathology of Cardio Vascular Disease (CVD) • Process of Atherosclerosis • Thrombosis • Causes and effects of Peripheral Vascular Disorders • Control of Cholesterol levels in the body

4. 7a) Atherosclerosis Atherosclerosis is the formation of plaques called atheromas beneath the endothelium in the wall of an artery Atheromas/plaques are formed of fatty materials consisting mainly of cholesterol, fibrous material and calcium Atheromas grow over time as more and more fatty materials are added to the initial plaque This causes thickening of the artery the artery loses its elasticity the diameter of the lumen of the vessel becomes reduced blood flow becomes restricted which increases blood pressure Atherosclerosis is the root cause of various cardiovascular diseases (CVD):- Angina Strokes Heart Attacks (myocardial infarctions) Peripheral vascular disease

5. 7b) Blood Clotting Blood clotting is a protective device triggered by damage to cells Cells can be damaged e.g. when Atheromas rupture they damage the endothelium cells. The presence of damaged cells leads to the release of blood clotting factors that change the inactive enzyme prothrombin into its active form thrombin Thrombin Fibrinogen Threads of fibrin (a soluble plasma protein) (an insoluble protein) Fibrin threads form a meshwork that clots the blood, seals the wound and provides a scaffold for the formation of scar tissue The formation of a blood clot (thrombus) is called thrombosis

6. 7c) Thrombosis • Atheromas on the inside lining of an artery can damage the endothelium leading to the formation of a thrombus. • If the thrombus breaks loose, it is called an embolus • An embolus is carried along by blood until it blocks a narrow vessel and restricts or blocks block flow • If an embolus blocks a coronary artery, it’s called coronary thrombosis, and may lead to myocardial infarction (heart attack) • A thrombus that causes a blockage in an artery to the brain may lead to a stoke • In both cases cells are deprived of oxygen leading to death of the tissues

7. 7d) Causes of peripheral vascular disorders The peripheral arteries are those other than the aorta, coronary (within the heart) and carotid arteries (supplies brain with blood) Peripheral vascular disease is the narrowing of the peripheral arteries due to atherosclerosis Peripheral vascular disease mostly affects leg arteries. Blood flow to the legs is restricted and pain is felt due to lack of oxygen Deep Vein Thrombosis (DVT) is the formation of a thrombus (blood clot) in a deep vein (most commonly in the lower leg). This causes the area to be painful, swell up and veins close to the skin surface can become engorged with blood. The thrombus can break off (embolus) and can block a pulmonary artery = pulmonary embolism The person experiences chest pains, breathing difficulties and palpitations If untreated the person can collapse or die suddenly

8. 7e) Cholesterol levels Lipids are a diverse group of organic compounds which include simple lipids (e.g. fats) and more complex substances (e.g. steroids) Cholesterol is a type of lipid found in the cell membrane Cholesterol is important because it is needed for the synthesis of sex hormones e.g. testosterone, oestrogen and progesterone The presence of cholesterol at an appropriate concentration in the bloodstream is essential to the health and well-being of the human body Cholesterol is synthesised by all cells, although 25% of total production takes place in the liver from saturated fats present in a normal balanced diet A diet high in saturated fats or cholesterol causes in increase in cholesterol levels in the blood

9. 7f) Low-density Lipoproteins (LDL) Lipoproteins are molecules containing a combination of lipid and protein, and are found in blood plasma which transports the lipids from one part of the body to another Low-density lipoproteins (LDL) are produced by the liver Most body cells synthesise LDL receptors which then embed in their cell membrane. When a molecule of LDL carrying LDL-cholesterol becomes attached to the receptor, the cell engulfs the LDL-cholesterol and the cholesterol is released for use by the cell When the body cell contains an adequate supply of cholesterol, a negative feedback system is triggered which inhibits the synthesis of new LDL receptors. Therefore less LDL-cholesterol in the blood is absorbed by body cells & circulates in the blood Some of the excess cholesterol is taken up by endothelial cells lining the inside of an artery, and is deposited in an atheroma.

10. 7g) Control of cholesterol levels

11. 7h) Excess Cholesterol Some of the excess cholesterol is taken up by endothelial cells lining the inside of an artery, and is deposited in an atheroma. This will happen to people that:- Eat a diet rich in saturated fats

12. 7i) High-density lipoproteins (HDL) Some of the excess cholesterol is transported by High-density lipoproteins (HDL) from body cells to the liver for elimination – which prevents a high level of cholesterol accumulating in the bloodstream Also, HDL-cholesterol is not taken into artery walls so does not contribute to atherosclerosis The healthy balance of HDL-cholesterol and LDL-cholesterol molecules is essential to ensure excess cholesterol is not in the bloodstream Normally, HDL molecules carries about 30% of blood cholesterol, and LDL molecules carry about 70%. If there is a higher ratio of HDL to LDL, there will be a decrease in blood cholesterol, thus decreasing the chances of atherosclerosis and CVD

13. Physical activity: Regular physical activity tends to raise HDL levels Low fat diet: Dietary changes aim to reduce the levels of total fat in the diet and to replace saturated with unsaturated fats Prescribed medications: Drugs called Statins lower cholesterol in the blood by inhibiting the enzyme essential for the synthesis of cholesterol by liver cells 7k) HDL and LDL in maintaining Health

14. Physiology & Health Questions KEY AREA 7 – Pathology of CVD • Testing Your Knowledge 1 Page 186 Q’s 1-4 2. Quick Quiz