Biology Unit 1 AQA The Heart & Heart Disease

The Heart

Two separate sides, left oxygenated, right deoxygenated.

Atrium - thin walled, only has to pump blood to ventricle.

Ventricle - thick walled, has to pump blood to lungs (therefore right thinner) and to the rest of the body.

There as two separate pumps, so the blood can increase it's pressure after visiting the capillaries in the lungs, ready to be pumped at high pressure around the rest of the body.

• Aorta - transports oxygenated blood from left ventricle to the body.
• Vena Cava - carries deoxygenated blood from the body to the right atrium.
• Pulmonary Artery - carries deoxygenated blood to the lungs.
• Pulmonary Vein - brings oxygenated blood from the lungs to the left atrium.

Heart muscle uses the blood from the coronary artery, branching off the aorta. If coronary artery gets blocked then parts of the heart can die - heart attack.

Cardiac Cycle

Diastole

• Blood returns from the pulmonary vein/vena cava to the atria.
• Atria begin to fill, the pressure in them rises.
• Pressure behind the atrioventricular valves is higher then in front, atrioventricular valves open.
• Blood flows into the ventricles.
• Atria and ventricle are still relaxed.
• Semi lunar valves are closed, pressure in front of the valves is higher then behind.

Atrial Systole

• Wave of electrical activity spreads from the SA node (pacemaker). Myogenic - contraction from within. Atrioventricular septum stops the wave crossing to the ventricles.
• Atria contract forcing remaining blood into the ventricles.
• Semi-lunar valves still closed, as the pressure in the aorta is still higher then in ventricles.

Ventricular Systole -

• Wave of electrical activity passes to the AV node. There is a delay before the reaction, so that the ventricles can fill up.
• Wave travels down to the bundle of his.
• Ventricles contract from the bottom up.
• Pressure in the ventricles increases, the pressure in front of the atrioventricular valves is higher then behind. Close.
• Pressure is higher behind the semi-lunar valves then in front, open.
• Blood moves into the aorta.

Cardiac Output is the amount of blood pumped out of one ventricle in one minute. Cardiac Output = heart rate x stroke volume cm3 perminute bpm cm3 when exercising stroke volume increases, due to heart working harder, resting heart rate decreases. heart rate = 60 seconds / time of one cycle

Heart Disease

Coronary Heart Disease - effects the coronary arteries, blood flow through these vessels may be impaired by an atheroma - can lead to a myocardial infarction.

Atheroma - fatty deposit forms within the wall of artery, begins as fatty streaks of white blood cells, enlarge to form atheromatous plaques, bulge into the lumen of artery leading to a reduction in blood flow.

Thrombosis - atheroma breaks through the lining of blood vessel, forms a rough surface interrupting smooth flow of blood - blood clot or thrombus. Can block the blood vessel, reducing the supply of blood to the tissues beyond.

Aneurysm - atheroma weakens the walls of the artery, the weak bits swell up like a balloon filled with blood. When these burst - hemorrhage - loss of blood to region of the body.

Smoking & coronary heart disease -

• Carbon monoxide - combines with hemoglobin, reduces the oxygen carrying capacity of the blood. - heart must work harder to supply enough oxygen = rise in blood pressure. May also be hard to supply the heart with oxygen during exercise.
• Nicotine - adrenaline, increases heart rate & raises blood pressure. Also makes red blood cells sticky - thrombosis.

High Blood Pressure - prolonged stress, diet and lack of exercise can increase blood pressure.

• heart must work harder to pump blood into the arteries that already have a high pressure.
• more likely to develop an aneurysm and burst.
• to resist pressure the walls thicken and harden restricting the flow of blood.

Diet -

• high levels of salt rise blood pressure