Edexcel A Level Biology, topic 1: Lifestyle, Health and Risk

Which factors effect an organism's need for a transport system? (3)

Size, surface area to volume ratio, level of activity

How do the circulatory systems of very small organisms work? And why?

Substances move around the organism by diffusion, all distances are short so diffusion is usually fast enough to meet needs

What is a mass transport system?

All particles in a liquid move in one direction around the body due to difference in pressure

How does an open circulatory system work? (3)

A simple heart pumps blood into cavities surrounding the animal's organs, substances diffuse from blood to cells, when heart muscles relax blood is drawn back into the heart through small valved openings

How does a closed circulatory system work? (3)

Blood is inclosed within tubes, heart pumping generates high pressure, forces blood around the body quickly

How does a single circulatory system work? (eg fish) (3)

Heart pumps deoxygenated blood to gills, carbon dioxide diffuses out and oxygen diffuses in, blood travels around rest of body before returning to the heart

How does a double circulatory system work? (2)

Right ventricle of heart pumps blood to lungs where it is oxygenated, blood returns to heart where left ventricle pumps it to the rest of the body

How are arteries adapted for their function? (3)

Narrow lumen to maintain high bp

Thick walls of muscle and elastic tissue so walls can expand and recoil after each beat

Thin outer layer of mainly collagen fibres to strengthen

How are veins adapted to their function? (3)

Wide lumen and thin walls because low bp

Low levels of collagen, smooth muscle cells and elastic fibres because no recoil and less strength needed

Semilunar valves to prevent blood from flowing backwards

How are capillaries adapted to their function?

Endothelium only one cell thick to allow for rapid diffusion

Vessels are only one cell wide to increase speed of flow

Describe atrial systole (3)

Low pressure blood flows into r and l atria from pulmonary veins and vena cava

Atrioventricular valves open due to high bp in atria

Blood flows into ventricles as atria walls contract

Describe ventricular systole (4)

Ventricle walls contract

Semilunar valves are forced open

Blood is forced into pulmonary arteries and aorta

Atrioventricular valves close dues to high bp in ventricle

Describe cardiac diastole (4)

Elastic recoil as atria and ventricles relax causing low bp in heart

High bp in pulmonary arteries and aorta close semilunar valves

Coronary arteries fill

Low bp in atria draws blood into heart from veins

What is the name of the valve between the right atrium and right ventricle?

Right AV valve (tricuspid)

What is the name of the valve between the left atrium and left ventricle?

Left AV valve (bicuspid)

What are the names of the valves at the entrance to the pulmonary arteries and aorta?

Semilunar valves

Describe the pathway of blood through the heart (13)

Superior and inferior vena cava

right atrium

right AV valve

right ventricle

Semilunar valve

pulmonary arteries

lungs

pulmonary veins

left atrium

left AV valve

left ventricle

semilunar valve

aorta

How is the heart's structure adapted for its function? (1)

Myocardium is much thicker on left side of heart because is needed to pump blood to entire body rather than just lungs

What are some of the main risk factors of atherosclerosis? (5)

Age

Smoking

Obesity

Excessive alcohol

Family history of CVD

Describe the steps leading to atherosclerosis (8)

Endothelium is damaged (often due to high bp)

Inflammatory response: large white blood cells from blood enter the wall

Causes accumulation of calcium salts, fibrous tissues and cholesterol

Fatty deposit builds up

Hard plaque forms on inner wall of artery as a result of calcium salts and fibrous tissues

Causes artery to harden (atherosclerosis)

Atheroma causes lumen to narrow, which increases bp

Positive feedback loop forms

Why can atheromas only form in arteries?

The bp is not high enough in veins or capillaries

How can atherosclerosis be treated? (3)

Medicine to reduce bp or cholesterol

Surgery to widen or bypass affected artery

Lifestyle changes

What can atherosclerosis lead to? (4)

Myocardial infarction

Stroke

Tissue death

Burst artery

What is an atheroma?

Build up of fatty deposits (mainly LDL) within the endothelium of an artery

Describe the blood-clotting process (8)

Platelets come into contact with damaged vessel wall

They become sticky to form a platelet plug

Platelets reacting with collagen in walls releases thromboplastin (triggering clotting cascade)

Thromboplastin with calcium and vitamin K from blood catalyses conversion of prothrombin into thrombin

Thrombin catalyses conversion of soluble fibrinogen into insoluble fibrin

Fibrin acts as a glue to trap more platelets and blood cells

Temporary platelet plug turns into blood clot

Once damage is repaired clot can dissolve back into blood

How can unwanted blood clotting be prevented? (6)

Prevent or treat atherosclerosis

Diet

Exercise

Not smoking

Bp medicine

Artery bypass

What are some of the main risk factors for CVD? (6)

Genetics

Diet

Age

High bp

Smoking

Inactivity

How does smoking increase risk of CVD? (4)

Carbon monoxide in smoke binds to haemoglobin (decrease oxygen supply to cells). Results in increase heart rate

Nicotine in smoke triggers production of adrenaline, increases heart rate and vasoconstriction so increased bp

Chemicals in smoke damage endothelium

Reduces HDL levels in blood

How does inactivity increase risk of CVD? (4)

Sufficient exercise:

Decreases bp

Helps maintain healthy weight

Increases HDL levels without effecting LDL

Deceases risk of type 2 diabetes

How do genetics affect risk of CVD? (1)

Apolipoprotein gene cluster is associated with CVD, some alleles increase risk some decrease

What are are apolipoproteins? (4)

Protein component of lipoproteins

Produces in liver and intestines

Stabilise structure of lipoproteins

Recognise receptor involved in lipoprotein uptake on plasma membrane of cells

What is apolipoprotein A (APOA)? (3)

Major protein in HDL

Helps move cholesterol from blood to liver for excretion

Mutations cause decreased HDL levels and increase risk of CVD

What is apolipoprotein B (APOB)? (3)

Major protein in LDL

Transfers cholesterol from blood to cells

Mutations cause increase in LDL levels so increase risk of CVD

What is Apolipoprotein E (APOE)? (3)

Major protein in HDL and VLDL

APOE gene has three alleles: E2, E3, E4

Having E4 slows removal of cholesterol from blood so increases risk of CVD

How does high bp increase risk of CVD? (1)

Can cause damage to the endothelium, resulting in atherosclerosis and therefore blockage of arteries

What is cholesterol and how is it transported around the body? (3)

Short lipid molecule

Insoluble

Must be combined with proteins to form soluble lipoproteins to be transported

What is LDL cholesterol and how does it effect the body? (3)

Low-density lipoprotein

Triglyceride of saturated fat, cholesterol and protein

Increases cholesterol deposition in blood so increases risk of atheromas

What is HDL cholesterol and how does it effect the body? (3)

High-density lipoprotein

Triglyceride of unsaturated fat, cholesterol and protein

Transports cholesterol from body tissues to the liver where it can be broken down and excreted

What is "good cholesterol"?

HDL cholesterol

What are the "bad cholesterols"?

LDL and VLDL cholesterol

How does diet effect risk of CVD? (3)

High LDL cholesterol diets will increase risk of developing atherosclerosis

High antioxidants diets will reduce the effect of radicals and reduce risk of CHD

High salt diets cause kidneys to retain water, increasing bp

What are radicals?

Oxidising agent that pulls hydrogen atoms from another molecule

What are the effects of free radicals? (2)

Cause damage to DNA, proteins and lipids

Damaged linked to development of CHD and cancer

What is the name of drugs used to reduce bp?

Antihypertentives

What are the four main types of anti hypertensives?

ACE inhibitors, calcium channel blockers, diuretics, statins

How do ACE inhibitors work? (1)

Decrease synthesis of angiotensin ii (hormone inducing vasoconstriction)

What are some of the side effects of ACE inhibitors? (2)

Arrhythmia and kidney disease

How do calcium channel blockers work? (1)

Prevent muscle contraction and therefore vasoconstriction

What are the side effects of calcium channel blockers? (1)

May worsen effects of heart failure

How do diuretics work? (1)

Decrease water uptake in the kidneys so lower bp

How do statins work? (1)

Inhibits enzyme involved in LDL production in liver

What are the side effects of statins? (1)

Can lead to some cancers

What is the name of the group of drugs used to prevent blood clots? (2)

Anticoagulants or platelet inhibitors

What are the two most commonly used platelet inhibitors?

Aspirin and clopidogrel

How does aspirin work?

Reduces the sickness of platelets and likely hood of clot formation

What is the major risk of combining aspirin and clopidogrel?

Bleeding in the gastrointestinal tract

What is one of the most commonly used anticoagulant?

Warfarin

How does warfarin work? (2)

Interferes with the production of vitamin K, reducing synthesis of clotting factors

What will happen if energy intake is greater than energy requirement?

Weight gain

What will happen if energy intake is less than energy requirement?

Weight loss

What will happen if energy intake is the same as energy requirement?

No change in weight

What determines somebody's basal metabolic rate (BMR)? (3)

Mass, height, age

What are the two methods of determining whether somebody is obese?

BMI and waist to hip ratio

What is the formula for BMI?

Body mass (kg) / height² (m²)

What are the two types of studies used to determine the impact of risk factors?

Cohort and case-control studies

How do cohort studies work? (2)

Large group who don't have condition

Compare risk factors and observe who go on to develop condition

How do case-control studies work? (3)

Group that have condition compared to group that don't

Info collected about past risk factors to see if there's a pattern

Important control group is representative of case group (age, sex)

What are the features of a good study? (5)

Clear aim or hypothesis

Sample representative of relevant population

Valid results

Large sample size

Control variable

People will often overestimate a risk when it is... (6)

Involuntary

Not natural

Unfamiliar

Dreaded

Unfair

Very small

What is coronary heart disease?

blockage of coronary arteries, limiting blood flow to the myocardium

What is oedema?

Build up of fluid in tissues causing swelling

What causes oedema? (5)

High bp at arterial end of capillary forces fluid and small molecules from plasma though gaps between cells in capillary walls into the intercellular space

This fluid is called tissue fluid or interstitial fluid

Blood cells and plasma proteins in capillary stop fluid from returning to blood through gaps in capillary wall

Fluid drains into network of lymph capillaries and then into the vena cave

If bp is too high fluid builds up causing swelling

Who tends to have higher BMRs? (4)

Males

Heavier people

Younger people

More active people

How does a bp monitor (sphygmomanometer) work? (4)

When cuff is inflated blood flow through artery in upper arm is stopped

Pressure above the cuff starts to build up

When cuff starts to deflate and blood can flow though artery again, pressure is measured (systolic)

A second reading is taken when no sound can be heard with a stethoscope below the cuff (diastolic)

What is systolic pressure?

Maximum bp when heart contracts

What is diastolic pressure?

Bp when heart is relaxed

What is considered a healthy range for systolic bp?

100- 140 mmHg

What is considered a healthy rage for diastolic bp?

60- 90 mmHg

How do you calculate heart rate from a cardiac cycle chart?

Divide 60 by the amount of time one cardiac cycle takes

What is stroke volume?

volume of blood pumped out by one ventricle with each beat

What is cardiac output? (2)

Volume of blood ejected by the heart in one minute:

cardiac output = heart rate x stroke volumne

What is the difference between a calorie and a Calorie? (3)

1000 calories = 1 Calorie

calorie = 1 calorie

Calorie = 1 kilocalorie

1 calorie = ____ joules

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