Bio topic 1: Cardiac cycle and clotting

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What occurs in systole?
The cardiac muscles contract & heart pumps blood out through aorta & pulmonary arteries
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What occurs in diastole?
Cardiac muscles relax & heart fills with blood
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Outline the stages of atrial systole.
Blood under low pressure flows into left & right atria from pulmonary veins & vena cava. Atria fills & blood pressure against atrioventricular valve increase = blood leaks into ventricles. When atria walls contract, more blood flows into ventricles.
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Outline the stages of ventricular systole.
After slight delay ventricles contract from base upwards. Increases pressure in ventricles & semilunar valves open. Blood pushed into pulmonary arteries aorta. Pressure of blood against atrioventricular valves forces them to close.
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Outline the stages of cardiac diastole.
Atria & ventricles relax & elastic recoil of the relaxing heart wall lowers pressure in atria & ventricles. Blood under high pressure in arteries & aorta drawn back towards ventricles, closes semilunar valves. Coronary arteries fill. Atria refills.
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Why do atria have thinner walls?
Blood flows through them at a low pressure & only have to pass the blood into the ventricles.
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Why to ventricles have thicker walls?
Have to deal with much higher pressure * have to push blood out to entire body.
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What is atherosclerosis?
The narrowing/blocking of an artery due to deposits of cholesterol & formation of plaques.
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What are some of the consequences of atherosclerosis
Could cause a stroke, myocardial infarction or gangrene. Narrowed arteries also have greater risk of bursting due to build up of blood.
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Why do only arteries get atherosclerosis?
Because the blood is under high pressure in the arteries due to the narrow lumen so higher chance of damage to artery walls.
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What causes the inflammatory response in atherosclerosis?
When the endothelium of the artery is damaged and then the inner lining becomes breached.
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What forms an atheroma?
The white blood cells from the inflammatory response move out of the blood vessel & into the artery wall. Then gather chemicals from the blood, esp. cholesterol which build up to form a fatty deposit called an atheroma.
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What forms plaque in the artery?
Calcium salts and fibrous tissue build up to form plaque on the inner wall of the artery
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Why does the formation of plaque make it easier to develop further cases of atherosclerosis ?
Plaque causes the artery to narrow, a narrower artery means higher blood pressure which increases the risk of the endothelium becoming damaged meaning more plaque etc.
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How is a temporary platelet plug formed when a blood vessel is damaged?
Platelets in the blood are activated by the exposed collagen in the broken blood vessel & change shape from flattened disks to spheres w. long thin projectiles. Stick to the exposed collagen & to each other forming the temp. plug.
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Where does thromoplastin come from & what does it do?
Thromoplastin is a protein produced by the activated platelets & damaged blood vessel cells. It activates series of enzymes that, in presence of calcium & vitamin K converts protein prothrombin to the enzyme thrombin.
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How is the fibrin mesh then formed?
The thrombin catalyses the conversion of the soluble plasma protein fibrinogen to the insoluble plasma protein fibrin. Once multiple fibrin molecules formed, polymerise to form fibrin mesh trapping red blood cells & platelets forming a blood clot.
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Other cards in this set

Card 2

Front

What occurs in diastole?

Back

Cardiac muscles relax & heart fills with blood

Card 3

Front

Outline the stages of atrial systole.

Back

Preview of the front of card 3

Card 4

Front

Outline the stages of ventricular systole.

Back

Preview of the front of card 4

Card 5

Front

Outline the stages of cardiac diastole.

Back

Preview of the front of card 5
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