Physiology, Health & Exercise

Physiology, Health & Exercise Lesson 5 Cardiovascular Disease

What happens when the CVS goes wrong? • Cardiovascular disease CVD • E.g: • Atherosclerosis • Thrombosis • Angina pectoris • Myocardial infarction (MI) • Hypertension • Stroke

Atherosclerosis • Disease process leads to CHD (coronary heart disease) & strokes • Fatty deposits either block the artery directly or increase the chance of the artery being blocked by a blood clot (thrombosis) • Blood supply can be blocked completely

Atherosclerosis • If occurs: • for long the affected cells are permanently damaged as starved of oxygen • in coronary artery myocardial infarction (MI) • Cardiac cells start to die within 3-4 minutes • in artery feeding brain  stroke • Brain cells start to die within 8-10 minutes • If causes narrowing of arteries of legs tissue death/gangrene • One of major causes of death in Westernised societies

Atherosclerosis-stages • Endothelial cells lining lumen of artery become damaged. • May be due e.g. to high blood pressure; toxins from cigarette smoke in blood; viral stress • Inflammatory response. • Large white blood cells (w.b.c) leave vessels and move to artery wall. W.b.c deposits chemicals from the blood particularly cholesterol. • Deposit builds upatheroma (Greek words- atheros = gruel & oma = tumour)

Atherosclerosis-stages • Calcium salts and fibrous tissue build up at the site to form a hard swelling called a plaque on the inner artery wall. • Artery wall loses some of its elasticity- i.e. hardens. • (Greek word for hardening is sclerosis- hence atherosclerosis) • Artery lumen becomes narrower. • More difficult for heart to pump blood- so rise in blood pressure

Atherosclerosis • Dangerous positive feedback loop as plaque raises blood pressure & • raised blood pressure increases chance of more plaques forming.

Atherosclerosis • Plaques tend to occur at sites where changes in the blood flow occur, e.g. where blood vessels branch • At this stage there my not be any symptoms • However if artery becomes very narrow/blocked then becomes very difficult to deliver enough blood to supply O2 and nutrients  now symptoms • Significance is particularly severe if coronary artery affected

Contributory/acceleratory factors to development of atherosclerosis • High blood pressure • Carbon monoxide in cigarette smoke • Having diabetes mellitus • High blood cholesterol levels

Atherosclerosis • Atherosclerosis can develop progressively from teenage to middle age. • Symptoms do not tend to arise until person over 50 i.e. until coronary artery blocked or a thrombus blocks an artery. • Aneurysm- when weakened artery walls bulge and eventually burst- fatal

Thrombus • The plaque has a rough surface so platelets attach • Platelets then change shape from flattened discs to spheres with long thin projections blood clot or thrombus at site which can block the artery • (Remember platelets create a network which becomes a blood clot)

Thrombus • If the thrombus breaks loose, embolus, which can then travel around the circulatory system until it reaches an artery that is too narrow to travel down. • If embolus reaches the coronary arteryembolism • Part of heart muscle diesMI • Severity depends on the area of heart muscle affected, size & location • If embolus reaches a brain artery  stroke

Thrombus

CHD Includes: • angina pectoris & • MI

Angina pectoris • Narrowing of coronary artery which limits O2 rich blood that reaches the heart muscle • Causes chest pain- angina pectoris • Usually experienced during exertion • If coronary arteries are narrowed by more than 50-70%, then the arteries cannot supply the needs of the heart muscle when it is exercising.

Angina pectoris • Heart muscle lacks O2 so respires anaerobically so produces lactic acid • Accumulated lactic acid causes pain in chest/left arm/shoulder • Shortness of breath & angina are first signs of CHD • Other symptoms are very similar to indigestion e.g. heaviness, tightness, burning pain & pressure behind breastbone • Rest removes the pain

Angina pectoris • Angina symptoms appear when atherosclerosis is quite advanced- i.e. diameter of coronary artery reduced by about 70% • There is no permanent muscle damage with angina • If angina occurs at rest then the coronary artery has narrowed to a critical degree

Myocardial Infarction (MI) • In UK over 270, 000 people suffer a heart attack each year. • Fatty plaque in coronary artery ruptures so the cholesterol released causes rapid blood clot formation • Blood supply to heart completely blocked • I.e. ischaemic- meaning without blood

Myocardial Infarction (MI)

Myocardial Infarction (MI) • When a heart attack is diagnosed quickly (within 1-2hours) and the patient reaches hospital in time, he or she may be given special clot-busting drugs that cause the clot to break up and allows the supply of blood to be restored • If muscle starved of O2 for long (3-4 minutes) causes the death of the cells i.e. heart attack or MI

Myocardial Infarction (MI) • If the zone of the dead cells is only over a small area- “silent infarction”- less likely to be fatal • If it causes the heart to beat irregularlyarrhythmia & can cause heart failure- so vitally important in diagnosis of heart disease • Approx 50% of patients who develop heart attacks have warning symptoms of angina prior to their heart attacks

Hypertension • Persistently high resting blood pressure • i.e. systolic blood pressure > 140 mm Hg • diastolic blood pressure > 90 mm Hg • >140/90

Hypertension

Hypertension • Hypertension is the major risk factor for many diseases, including CHD Contributory factors: • Diet (high salt, high fat) • Obesity • Smoking • Genetic predisposition • Stress

Hypertension Mostly controlled by: • Alteration to diet • Exercise • Medication • 20% of adult UK population suffer from hypertension and are unaware that they have it!

Stroke • Thrombus in cerebral artery • Embolus in cerebral artery • Haemorrhagic stroke- blood vessel supplying blood to brain bursts • All cause damage or death to brain cells

Physiology, Health & Exercise