Unit 1 : The body and its diseases

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Balanced Diet
Balance of energy and food groups
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Aids movement of food through gut
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Need a constant supply to replace water lost through urinating, breathing and sweating
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Provides energy
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Fats (Lipids)
Make up cell membranes and physically protect organs
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Growth, repair of tissues and make enzymes
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Vitamin D - calcium absorption
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Mineral salts
Iron - Haemoglobin, Calcium - Blood formation
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Diet high in fruit and veg
Good source of vitamins, minerals and fibre, can reduce risk of heart disease
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Diet low in salt and fat
Lower blood pressure, reduce risk of heart attack/stroke, sat fats increase cholesterol leading to heart disease
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Glycaemic Index
How quick carbohydrates in different foods raise blood sugar levels after eating, value from 0 - 100
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Glycaemic Load
Takes into account the amount of carbohydrates in an average portion of food
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Type 2 diabetes
Insulin produced doesn't work well - cells become resistant to insulin
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Body Mass Index - 30+ increase risk of heart disease, low life expectancy
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Link of type 2 diabetes and obesity with weight
Body fat causes cells to become resistant to insulin
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Gut bacteria
Large numbers in the colon, in digestive system. Help body break down indigestable carbs, releasing extra nutrients. Prevent growth of harmful bacteria by competing with them
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Vitamin K
Some gut species produce Vitamin K, needed by liver to synthesise thrombin, an enzyme needed for blood clotting.
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Isotonic Sports Drinks
Replace glucose, electrolytes and water used up in exercise, same concentration of solutes as body fluid, helping absorption
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Large molecules made of smaller molecules that are joined together by condensation reactions
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Why do large molecules have to be broken down?
Have to be hydrolysed to smaller molecules to be absorbed in the gut
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What's food made up of?
Same as humans, fats, proteins and carbohydrates
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Large biological molecules
Limited to carbohydrates, lipids and proteins
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Single sugar molecules, when 2 join together a disaccharide is formed
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More than two monosaccharides joined together
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Glucose joins to make what...?
Maltose, starch, glycogen and cellulose
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Proteins primary structure?
Sequence of amino acids in the polypeptide chain
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Proteins secondary structure?
Hydrogen bonds from between amino acids, alpha helix or beta pleated sheet forms
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Proteins tertiary structure?
More bonds (hydrogen or ionic) or disulfide bridges form between different parts of polypeptide chain, forming 3D shape
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What are proteins made of?
Amino acids
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What are fats made of?
Glycerol and fatty acids
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What are digestive enzymes?
Allow hydrolysis reactions to take place rapidly under certain conditions in the gut
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Physiological Conditions of digestive enzymes
Body temperature - 37 degrees celcius, Alkaline conditions in the small intestines for carbohydrase and lipase to work; made by the liver producing bile which neutralises stomach acid, Hydrochloric acid made by stomach - acidic conditions for pepsin
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Chromatography and calculation of the Rf value
Technique by which components of a mixture can be identified
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Rf value
Distance travelled by spot/Distance travelled by solvent
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What are enzymes?
Catalysts that lower activation energy through formation of enzyme-substrate complexes
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Lock and Key
Each substrate will only fit into the active site of one specific enzyme, substrate gets very close to active site, thus lowering activation energy
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Induced fit
Enzyme has a basic shape that's flexible which changes when substrate collides with it, making active site close fit for substrate, lowering activation energy needed for reaction
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Temperature on rate of reaction
More heat, more kinetic energy so molecules move faster, making enzymes more likely to collide. Energy also increases meaning a reaction likely to happen. If temp too high, reaction stops,
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pH on rate of reaction
Above/Below optimum pH, the H+ ions and OH- ions can mess up ionic and hydrogen bonds which hold tertiary struture together, making active site change shape. - Enzyme gets denatured
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Substrate Concentration on rate of reaction
The higher the substrate concentration, the faster the reaction. More substrate molecules, more chances of collisons between enzyme and substrate. Until Saturation point, where active sites are full and adding more makes no difference
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Humans can digest starch but not cellulose
Different types of carbohydrates. Bodies produce enzyme amylase - speeds up digestion of starch into simple sugars. Cellulose doesn't fit into active site of amylase, body doesn't produce enzymes that it can fit into so we can't digest it
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Causes of lactose intolerance
If body doesn't have enough of the enzyme lactase which digests the sugar 'lactose' found in milk
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Symptoms of lactose intolerance
Fermented by bacteria, bacteria causes stomach cramps, excessive flatulence (wind), bloating and nausea. Sugar lowers water potential of gut contents causing diarrhoea
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Enzymes are analytical reagents, (substances used in analytical tests)
Specific so make the test accurate, React with low concentrations of substrate making test sensitive, They work quickly.
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Glucose Oxidase and Peroxidase in testing for glucose
Testing urine for glucose could diagnose diabetes, as normally doesn't contain it. Special strip dipped in urine. Coloured square at end with two enzymes (title) and pink dye. G.O catalyses reaction of glucose, oxygen and water.
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Glucose Oxidase and Peroxidase in testing for glucose 1
Making gluconic acid + hydrogen peroxide (latter made if glucose present). Latter reacts with pink dye, turning it blue. This reaction catalysed by peroxidase. H.P + pink dye = blue dye + water
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Enzymes in medicine (alpha-1-antitrypsin
Trypsin from smoking causes (emphysema) lung disease, by damage to a protein called elastin, an elastic that allows alveoli to go back to normal shape after breathing out, treatment is alpha-t-antitrypsin
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What is alpha-1-antitrypsin
It's produced in the liver and circulates in the bloodstream, it inhibits the action of the enzyme elastase, which breaks down elastin in healthy lung tissue, but when inhibited by alpha-1-antitrypsin, it only breaks down old/damaged tissue
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Enzymes in medicine (Pancreatic Enzyme Replacement Therapy)
Help CF sufferers digest food. Artificial enzymes in capsules are given to patients before/with meal to replace digestive enzymes that're normally released by the pancreas. They can then digest/absorb proteins, carbs + fats
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What do diseases do to enzymes?
Disease can result in changes in the concentration and distribution of enzymes in the body.
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Pancreatitis and enzymes
Digestive enzymes get activated too early in pancreatitis sufferes, and begin to digest the pancreas, as bits are killed off, the ability to produce enzyme is affected resulting in changes of concentration and distribution of enzymes.
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What does efficient gas exchange require?
A large surface area, a short diffusion pathway and a large concentration gradient, maintained by ventilation.
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Pancreatitis and enzymes 1
It may result in increased concentration of digestive enzymes in the blood, or decrease in concentration of enzymes in the gut. Causing digestive problems, abdominal pain, nausea and vomiting
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How's gas exchange impaired in people with cystic fibrosis?
The epithelium lining has goblet and ciliated cells. CF sufferes have thick mucus which the cilia can't waft upwards, so mucus builds up. Making volume of air able to pass through lower so concn gradient lower.
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Gas exchange in the lungs
As we breathe in, air enters the trachea which then splits into 2, one to each lung. Each bronchus then branches off into smaller tubes called bronchioles which end in small 'air sacs' called alveoli.
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What's Fick's Law?
Surface area x concentration gradient/diffusion pathway
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How else does CF reduce the efficiency of gas exchange?
A 'mucus plug' may form. Mucus completely blocks airway, preventing air reaching a whole section of alveoli, thus decreases concentration gradient across them.
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What's the fluid mosaic model?
Phospholipid molecules form a continuous double layer (bilayer), this is 'fluid' as phospholipids are constantly moving. Protein molecules are scattered through the layer, like tiles in a mosaic
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Active transport
A solute attaches to a specific carrier protein in the plasma membrane of the cell, the carrier protein changes shape and moves it across the membrane releasing it on the other side. Energy from ATP moves solute against concentration gradient
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Osmosis in terms of water potential
Diffusion of water molecules across partially permeable membrane from high water potential to low water potential. Water will diffuse both ways, but net movement wil be side with lower potential.
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Water potential
The potential of water molecules to diffuse out of or into a solution
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CFTR protein
Plasma-membrane protein that actively transports CL- ions out a cell. In CF, the tertiary structure of the protein is altered, so Cl- ions aren't transported out of cell. Thus affecting water potential of mucus in respiratory tract = thicker mucus
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Why are CF sufferes prone to lung infections?
Mucus is hard to get rid of. Trapped bacteria have tme to multiply in warm, moist conditions. Large numbers cause serious infections like pneumonia. Immune system cells are hard to penetrate thick mucus and kill bacteria
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Small organelle free to float in cytoplasm or on rough ER. Site where proteins are made.
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Endoplasmic reticulum
Smooth-membranes enclosing fluid-filled sacs, Synthesised and processes lipids. Rough- membranes covered in ribosomes, folds and processes membranes
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Golgi body
Group of fluid filled, flattened sacs. Processes and packages new lipids and proteins
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small fluid-filled sac covered in membrane. Transport substances between organelles and plasma membrane
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Eukaryotic Cells
Plant and animal cells,
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Prokaryotic Cells
Smaller, simpler, bacteria
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Role of mitochondria in supplying ATP for active transport
ATP is produced in organelles called mitochondria, molecule binds to carrier protein, ATP also binds to this. Carrier protein changes shape and energy from breakdown is used to transport molecule across membrane.
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Thick mucus in the gut of a CF sufferer makes food not digest properly
Goblet cells are in digestive system around pancreas and duodenum. Digestive enzymes released by pancreas can't get through thick mucus that blocks duct leading to small intestine so food not digested properly
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Thck mucus in gut of CF sufferer makes food not absorb properly
Mucus blocks release of substance that neutralises stomach acid from glands in the duodenum. If they're not present, lining of duodenum may get damaged.
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CF sufferers need to take enzyme capsules before meals
Contain pancreatic enzymes. Lipase-digest fats. Protease-digest proteins. Amylase-digest starch
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Structure of prokaryotic cell
Flagellum-movement (not all have one) DNA-floats free Plasmids-small loops of DNA (not always present) Capsule-Protects from attack by cells of immune system and keeps moist (not all have them) Cell wall-supports cell 'peptidoglycan'
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Structure of prokaryotic cell 1
Cell membrane-control movement of substances in and out of cell (made of proteins and lipids) Ribosomes-site of protein synthesis, free in cytoplasm
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How do microorganisms cause disease?
Damage the cells of the host and produce toxins
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Salmonella food poisoning
Chocolate, eggs, chicken. Bacteria infect gut epithelial cells, divide, produce toxins preventing absorption of water in large intestine causing diarrhoea. Stomach ache, fever. Thoroughly cook food. Sufferers have lots to drink and rest.
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Droplet infection. Invade white blood cells in lungs, lay dormant for years. When immune system weakened, they replicate and spread to other tissues. Weight loss and coughing. BCG vaccine and antibiotics. Antibiotic-resistant strains are big problem
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How can antibiotics be used to treat bacterial disease
Interfering with bacterial metabolism, limited to prevention of cell wall synthesis and protein production.
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What do viruses cause?
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Core-contains genetic material (RNA) and some proteins like enzyme reverse transcriptase. Outer coating-Protein called Capsid. Extra outer layer-Envelope. Made of membrane stolen from cell membrane of previous host.
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HIV replication
Envelope attaches to receptor molecule, capsid is released into cell where it uncoats and releases RNA into cells cytoplasm. Reverse transcriptase makes complementary strand of DNA from viral RNA template.
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HIV replication 1
Double stranded DNA is made and inserted into human DNA. Host cell enzymes make viral proteins from viral DNA in human DNA. Viral proteins then assembled into new viruses which bud from cell and infect other cells.
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Initial symptom-minor infection of mucous membrane. Then no. of immune system cells decrease, more susceptible to more serious infections like chronic diarrhoea and TB. Lastly, low no. of immune system cells and suffer serious infections which kill
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How HIV is spread
Unprotected sex, Infected bodily fluids, mother to foetus.
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Antibiotics can't treat viruses
Viruses don't have their own enzymes and ribosomes so antibiotics can't inhibit them as they don't target human processes .
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Antigens and antibodies
Antigen-on cell surface of pathogen (bacteria). Activate immune system. Antibody-proteins that bind antigens to form an antigen-antibody complex.
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Role of T-Cells in response to antigens
Proteins on its surface bind to antigens presented by phagocytes which activate T-Cell which either releases substances to activate B-Cells or attach to antigens on a pathogen and kill them.
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Role of B-Cells in response to antigens
When antibody on surface of a B-Cell meets complementary shaped antigen, it binds to it. This activates B-Cell which divides by mitosis into plasma cells.
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Role of plasma and memory cells in producing primary response
When antigen enters body for first time it activates immune system - P.R. T and B cell sproduce memory cells that record specific antibodies needed to bind to antigen.
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Role of plasma and memory cells in producing secondary response
If same pathogen enters the body, memory B-cells divide into plasma cells which make right antibody to antigen. Memory T-cells divide into correct type to kill the cell carrying the antigen.
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Passive immunity
Antibodies may be acquired naturally through the placenta and via lactation as well as artifically.
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Active immunity
Vaccines contain attenuated or dead microorganisms or isolated antigens which may be used as the basis for vaccines
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Risks of mass vaccination programs
May cause side effects
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Benefit of mass vaccination programs
Person vaccinated won't get the disease and it creates herd immunity - if most people in community are vaccinated, it becomes rare.
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Use of monoclonal antibodies 'Magic bullets'
Target specific substances and cells. Targetic medication to specific cell types by attaching a therapeutic drug to an antibody. Can be used in medical diagnosis - testing for hCG in pregnancy test kits
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What are the events during the cardiac cycle?
SAN stimulates an impulse to the atrial walls. Right + left atria contract at same time, increasing pressure inside chamber. Blood passes through Atrioventricular valves into the ventricles.
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What are the events during the cardiac cycle? 2
Electrical impulse is transferred from SAN to AVN with short time delay, allowing atria to empty. Impulses go to Bundle of His along to Purkyne fibres, causing right and left ventricle walls to contract at same time from bottom up. Atria relaxes.
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What are the events during the cardiac cycle? 3
Ventricles contract, increasing their pressure which is higher than in the atria. Atrioventricular valves shut + semi lunar valves open, blood forced out of aorta + pulmonary arteries. Ventricles + atria relax.
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What are the events during the cardiac cycle? 4
Pressure in pulmonary artery and aorta cause SL valve to shut. Atria fills again due to high pressure from vena cava and pulmonary vein, and so pressure in aorta increases again.
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Myogenic stimulation
It can contract and relax without receiving signals from nerves.
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Use of artificial pacemakers to regulate heart activity
Device implanted under the skin and has a wire going to the heart. It produces an electrical current to stimulate the heart to beat.
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Atheroma formation
If endothelium (inner lining) gets damaged, white blood cells and lipids from the blood clump together under the lining forming fatty streaks. More white blood cells, lipids and connective tissue build up and harden, forming a fibrous plaque-atheroma
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Atheroma causes coronary artery to get narrow, reducing blood supply to parts of heart muscle. So decrease in oxygen causing heart pain.
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Narrow arteries from atheroma = increased blood pressure, which going through a narrow space causes the blood to push the inner layers of artery through the outer elastic layer, forming balloon like swelling. It may be burst and causes a haemorrhage
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Atheroma plaque can rupture the endothelium, damaging artery wall, platelets and fibrin accumulate here and form a blood clot. This could cause a complete blockage of the artery or get dislodged and block a vessel elsewhere.
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Deep Vein Thrombosis
May occur as a result of prolonged inactivity, ageing and long-haul flights. Can be reduced by taking drugs that prevent or slow blood clotting, compression stockings and move around regularly.
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Myocardinal Infarction
Coronary artery becomes completely blocked causing an area of the heart muscle to be completely blocked off, no oxygen. A heart attack happens causing damage/death of heart muscle. Pain in chest, sweat, short breath. Large areas=heart failure=fatal
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Deflated balloon inserted into narrow coronary artery and inflated. This compresses atheroma plaque and stretches the artery. Improves supply of blood to heart muscle so enough O2 for respration
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Coronary by-pass surgery
Open heart surgery. Bit of healthy blood vessel from another part of body is used to bypass the narrowed region of artery, improving blood supply.
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Drugs that lower blood pressure by reducing the strength of the heartbeat.
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Poor diet leads to cardiovascular disease
Blood cholesterol high, cholesterol is fatty deposits contributing to atheroma, high salt levels increase blood pressure
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Cigarettes leads to cardiovascular disease
CO combines with haemoglobin and reduces amount of O2 transported in blood. Smoking decreases amount of antioxidants in blood which protect cell damage.
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Structure of capillaries
Smallest of blood vessels. Metabolic exchange occurs-substances are exchanged between cells and capillaries. There are network of capillaries in tissue increasing surface area for exchange. Walls only 1 cell thick = speed up diffusion of substances
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Formation of tissue fluid
At start of capillary bed, near artery, pressure in capillaries is greater than in tissue fluid. This difference forces fluid out of capillaries, into spaces around cells forming tissue fluid.
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Formation of tissue fluid 1
As it leaves, the pressure drops in capillaries so its lower at end of veins. So water potential at end near vein is lower than water potential in tissue fluid, so some re-enters the capillaries from tissue fluid at vein end by osmosis.
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Formation of tissue fluid 2
Excess fluid drained into lymphatic system where its transported from the tissues and dumped back into circulatory system.
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H.B.P cause build up of tissue fluid, formation is increased as more fluid's pushed out of capillaries. The H..B.P makes it harder for water to move back into capillaries, so a swelling occurs of accumulated tissue.
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Aids movement of food through gut



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Need a constant supply to replace water lost through urinating, breathing and sweating


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Provides energy


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Make up cell membranes and physically protect organs


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