Biology Edexcel AS - Topic 1

These are very, very brief notes. They're not sufficient for full-scale revision but more for having something brief to read over and test yourself on just before going in for the exam. 

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  • Created by: Millie
  • Created on: 04-05-13 14:50
Open circulatory system
Blood circulates in large open spaces. A simple heart pumps blood out into cavities surrounding the animal's organs. Substances diffuse between the blood and cells. The heart relaxes and the blood in the cavity is drawn back into the heart.
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Benefits of a closed circulatory system
Allows higher blood pressure as the blood is forced through narrow tube, so the blood flows faster = more efficient at delivering substances around the body. Allows the organism to have a greater metabolism + active The organism can be larger in size
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Single circulatory system
The blood flows through the heart once for each circuit around the body,
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Single circulatory system ( fish)
The heart pumps deoxygenated blood to the gills. Gaseous exchange occurs. The oxygenated blood leaves the gills and flows to the rest of the body
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How blood flow back to the heart is helped by skeletal muscles
When skeletal muscles contract they exert pressure on the veins forcing it ( and its valves) open
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Cardiac cycle stage 1
Blood under low pressure returns to the heart and flows into the left and right atrium from the pulmonary veins and vena cava
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Cardiac cycle stage 2
The pressure in the atria increases eventually forcing the AV valves ( tricuspid and bicuspid) open and blood starts to flow into the ventricles
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Cardiac cycle stage 3
Th atria walls contract, forcing more blood into the ventricles
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Cardiac cycle stage 4
Atrial systole is followed immediately by ventricular systole. The ventricles contract forcing blood into the artieries (pulmonary and aorta). The pressure against the AV valves closes them to prevent backflow
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Cardiac cycle stage 1
Blood under low pressure returns to the heart and flows into the left and right atrium from the pulmonary veins and vena cava
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Cardiac cycle stage 2
The pressure in the atria increases eventually forcing the AV valves ( tricuspid and bicuspid) open and blood starts to flow into the ventricles
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Cardiac cycle stage 3
Th atria walls contract, forcing more blood into the ventricles
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Cardiac cycle stage 4
Atrial systole is followed immediately by ventricular systole. The ventricles contract forcing blood into the artieries (pulmonary and aorta). The pressure against the AV valves closes them to prevent backflow
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Cardiac cycle stage 5
The atria and ventricles during diastole. Elastic recoil of the relaxing heart walls lowers pressure in the atria and ventricles. Blood under high pressure in the arteries is drawn back to the ventricles, closing the semilunar valves.
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Cardiac cycle stage 6
The coronoary arties fill during diastole. Low pressure in the arteries draws blood into the heart from the veins
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Why does the left side of the heart have a thick muscular wall?
It has to pump blood all around the body. The right side has a thinner muscular wall cos it only has to pump blood to the pulmonary artery.
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Why is blood clotting a vital defense mechanism for the body?
1. minimise blood loss 2. to prevent the entry of pathogens 3. provide a framework for repair
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Stroke
blood supply to part of the brain is cut off
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Heart attack / myocardial infarction
blockage of coronary vessels
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Angina
narrowing of coronary arteries which causes pain
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Reduce risk of CVD
Stop smoking. moderate regular exercise. reduce alcohol consumption. lower cholesterol / sat fat intake
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Types of drugs to treat CVD
Antihypertensives. Statins. Anticoagulants. Platelet inhibitors
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Antihypertensives
Reduce high blood pressure
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Diuretic ( anti hypertensive) + side effect
Increase vol. of urine produced, which lowers the blood. vol and bp + can cause muscle cramps, nausea and dizziness
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ACE inhibitors ( anti hypertensive) + side effect
inhibit the production of the enzyme angiotensin, which normally causes arterial constriction and a rise in bp+ cough, dizziness, heart arrhythmia, impaired kidney function
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Statins + side effects
Drugs that reduce blood cholesterol by blocking the liver enzyme that makes LDL cholesterol+ muscle aches, nausea, constipation/ diarrhea
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Anticoagulants + example+ side effect
Warfarin -it affects the synthesis of clotting factors +risk of uncontrolled bleeding
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Platelet inhibitory drug + example +side effect
clopidogrel or asprin - makes platelets less sticky + aspirin irriates the lining of the stomach and can cause bleeding. If both are used together the risk of bleeding is increased subtantially
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A diet to reduce the risk of CVD
Energy balanced, reduced sat fat, more polysat fats, reduced cholesterol, reduced salt, eat more fruit and veg ( antioxidants)
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Other cards in this set

Card 2

Front

Allows higher blood pressure as the blood is forced through narrow tube, so the blood flows faster = more efficient at delivering substances around the body. Allows the organism to have a greater metabolism + active The organism can be larger in size

Back

Benefits of a closed circulatory system

Card 3

Front

The blood flows through the heart once for each circuit around the body,

Back

Preview of the back of card 3

Card 4

Front

The heart pumps deoxygenated blood to the gills. Gaseous exchange occurs. The oxygenated blood leaves the gills and flows to the rest of the body

Back

Preview of the back of card 4

Card 5

Front

When skeletal muscles contract they exert pressure on the veins forcing it ( and its valves) open

Back

Preview of the back of card 5
View more cards

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