Heart and circulation
Moves substances around the body.
Unicellur organisms- needs met by diffusion alone
Multicellular organisms-needs met using a circulatory system
Open circulatory system
Blood circulates in large open spaces
It is pumped into cavities to allow diffusion between blood and cells
When the heart relaxes blood is pulled back from the cavities through small valved openings along its length.
Heart and circulation
Closed circulatory system
Blood is enclosed within tubes so it is at higher pressure. Consequently it travels faster and is therfore more efficient to meet the requirements of organisms with a large surface area to volume ratio (multicellular).
Blood leaves the heart under high pressure before flowing from the arteries>arterioles> capillaries>venules>veins.
Capillaries are close to cells to allow substance exchange.
Blood then returns to the heart.
There is 2 types of circulatory system:single and double.
Single and double circulatory systems
Single circulatory system
The heart pumps deoxygenated blood under high pressure to the (gills) where diffusion/gas exchange takes place.
The oxygenated blood then leaves the gills and flows around the body before returning to the heart.
Double circulatory system
The right ventricle pumps deoxygenated blood to the lungs to receive oxygen.
The oxygenated blood returns to the heart where the left ventricle pumps the blood to the rest of the body.
This allows the system to maintain efficiency through a high metabolic rate
The transport medium
Plasma is comprised of water and dissolved substances (carbon dioxide, oxygen and food/glucose).
It transports: proteins, urea, salts and antibodies.
RBC,WBC, and platelets are carried in the blood.
It helps regulate temperature.
Water : A small polar molecule (uneven distribution of charge) , H+/O-, hydrogen bonding (H+ attracted to O- on other molecules, this makes water a liquid), chemicals dissolve in it easily (for biochemical reactions in the cytoplasm), ionic compounds become hydrated as Na+ is attracted to the O- and Cl- is attracted to the H+ ultimately causing separation, cells react with the water to carry out condensation and hydrolysis reactions, it has a high specific heat capacity (large amount of energy input only causes a small rise in temperature which helps avoid rapid internal changes.
Heart and blood vessels
Pulmonary vein (oxygenated from lungs)
Vena cava (deoxygenated blood from arms, head and lower body)
Away from heart
Aorta (main transporter, oxygenated blood to the body)
Pulmonary artery (deoxygenated blood to the lungs)
Atrioventricular valves prevent backflow of blood into the atria.
Semilunar valves prevent backflow of blood into the ventricles
Comparison between arteries/veins/capillaries
Arteries: Narrow lumen, thick walls , more collagen, elastic fibres and smooth muscle, and they have no valves.
Veins: Wide lumen, less collagen, elastic fibres and smooth muscle, thin walls and they have valves.
Capillaries: One cell thick, and 10 microns in diameter.
Elastic fibres are needed for stretch and recoil.
Collagen is needed to form a rigid and durable structure.
Smooth muscle is needed for constriction and dilation.
How does blood move through vessels?
Systole- blood is forced into the arteries which stretch to accomodate the blood.
Diastole-blood propelled forward due to stretch and recoil of the artery wall behind the blood (pulse).
When blood reaches the arterioles and capillaries there is a steady flow of blood which allows exchange of substances in the capillaries between the blood and surrounding cells (rapid diffusion) .
In the veins blood flow is assisted by skeletal muscle contractions and breathing.
Breathing causes low pressure in the thorax which draws blood back in to the heart.
Valves prevent backflow.
The heart can't directly use the blood in its chambers so the heart muscle is supplied with blood from the coronary arteries
Cardiac cycle : one complete sequence of filling and pumping blood (alternate contractions of chambers).
Cardiac cycle/atrial systole
Systole (contraction)-heart pumps blood out of the aorta and pulmonary arteries.
Diastole(relaxation)-heart fills with blood
Skeletal muscle contractions and breathing cause blood to return to the heart.
Blood under low pressure flows from vena cava and pulmonary veins into the atria.
Atrioventricular valves ope and blood leaks into ventricles.
Atria walls contract forcing more blood into the ventricles.
Cardiac cycle/ventricular systole
Ventricles contract from the base of the heart up wards which increases the pressure in the ventricles.
Blood is pushed out of the arteries.
Atrioventricular valves close to prevent backflow.
Atria and ventricles relax.
Elastic recoil lowers pressure.
Blood in arteries drawn towards ventricles so semi lunar valves shut.
Coronary arteries fill.
Low pressure in the atria draws blood from the veins.
Leads to coronary heart disease and strokes.
Fatty deposits block artery or increase chance of being blocked by a blood clot (thrombosis).
Heart -> myocardial infarction (heart attack) Brain -> stroke
Endothelial damage ( smoking/carcinogens, high blood pressure etc)
Inflammatory response where WBCs and cholesterol accumalate which causes an atheroma.
Calcium salts and fibrous tissue cause the atheroma to harden into a plaque, whcih reduces vessel elasticity , and ultimately narrowing the arteries, so blood pressure rises.
This can result in positive feedback.
Why does blood clot?
Platelets touch damaged cell wall, changing from flat discs to spheres with projections which attavh themselves to the exposed collagen to form a platelet plug.
This releases a substance whch activates more platelets.
There's a cascade of changes . Prothrombin is changed into thrombin, which changes fibrinogen (soluble) into fibrin (insoluble).
This forms a tangled mesh which traps blood cells and makes a clot.
Coronary heart disease
Narrowed coranary arteries limit the blood reaching the chest muscle, which results in angina.
The heart respires anaerobically, creating the by product of lactic acid and causing pain.
If the fatty plaque rupturescholesterol is released and there is rapid clot formation as the blood supply is blocked.
The heart muscles doesn't receive blood (ischaemic) .
Cells may be damaged permanently (if the zone of the dead cells is small the less likely it is that the heart attack is fatal).
Symtpoms include shortness of breath, arrhythmia, and fatigue.
Strokes occur when blood flow to the brain is interrupted.
Symtoms include paralysis on one side, loss of vision, slurred speech and numbness.
An artery narrows which causes a build up of blood.
The artery bulges and an aneurysm forms.
It ruptures which causes shock and blood loss which can be fatal.
Can be detected in physical examinations and ultrasounds.
Hypertension (High blood pressure)
Blood pressure : the measure of the hydrostatic force of blood against the wall of blood vessels.
Arterial pressure is highest during ventricular systole.
Systolic pressure/Diastolic pressure (normal = 145/85)
Inflatable cuff attached to a gauge that measures pressure.
When cuff inflates arterial blood flow stops.
As cuff is released blood flows through artery (systolic pressure)
Stethoscope hears flow of blood positioned on artery,when this can't be heard it is diastolic pressure.
Blood pressure is measured in mmHg/Kpa
What determines blood pressure?/Oedema
Peripheral resistance is friction between blood and vessel walls which impedes blood flow.
Arterioles and capillaries have a greater surface area, resisting more flow which lowers blood pressure.
In the arteries blood pressure fluctuates.
Constriction increases resistance.
Any factor that causes constriction leads to elevated blood pressure (adrenaling, natural loss of elasticity).
High blood pressure leads on to atherosclerosis.
Fluid build up in tissue causing swelling.
Arterial end of the capillary blood is under high pressure which forces fluid and small molecules found in the plasma out of the capillaries into intercellular spaces, forming tissue fluid.
The capillary walls only allow small molecules through (not proteins or blood cells)
If blood pressure is raised more fluid may be forced out of the capillaries causing fluid accumulation and oedema.
Carbohydrates, lipids and proteins all store energy,
(Least energy) carbohydrates->proteins->alcohol->lipids (most energy)
calorie is the quantity of heat energy required to raise the temperature of 1 cm^3 of water by 1 degree.
1 kilocalorie=1000 calories
1000 calories = 1 Calorie
1 calorie=4.18 joules
Energy content of foods is measure in joules (j) (1 Kj=1000j)
Turn 2000 kj into calories and Calories
2000000/4.18 = 478468.8995 calories
Monosaccharide is a single sugar unit. It is a rapid source of energy which causes a sharp rise in blood pressure.
Disaccharide is 2 sugar units joined together by condensation reaction to form a glycosidic bond.
Long straight, or branched chains form polysaccharides.
Monomer is an identical or similar subunit.
(CH20)n (n= number of carbons)
They have between 3 and 7 carbons.
Most have 6 carbons and are called hexose sugars (glucose, galactose and fructose)
Hexose is a ring structure.
Fructose=seed dispersal and dieting
2 single sugar units joined together by a condensation reaction to form a glycosidic bond (which can be split by hydrolisis).
A water molecule is released.
Some examples are: sucrose, maltose and lactose.
Sucrose= fructose and glucose (form of sugar transported in a plant)
Maltose=glucose and glucose (formed when amylase breaks down starch)
Lactose=glucose and galactose (used in milk, hydrolyse lactose to give glucose and galactoseto give more tolerance)
Polysaccharides and disaccharides must be broken down into monosaccharides before being absorbed. Monosaccharides are released slowly so don't cause swings in blood pressure like eating monosaccharides.
Polymers made from simple sugar monomers, joined by glycosidic links into long chains)
Starch (plants): energy store, compact, low solubility, no osmotic effect.
Cellulose (plants): non starch polysaccharide.
Glycogen (animals): energy store, compact,low solubility, no osmotic effect (instead of starch), branched, rapily hydrolysed.
Starch is made of amylose and amylopectin.
Amylose : 1,4 glycosidic links, spiral shape.
Amylopectin: 1,4 and 1,6 glycosidic bonds , branched.
Cellulose: dietary fibre (non starch polysacharide), straight chain, indigestible in the human gut, helps the movement of material through digestive tract.
Supply double the energy of carbohydrates (useful if a lot of energy is required from a small amount of food).
Large amounts of energy can be stored in small objects like seeds.
Insoluble in water, soluble in alcohol (ethanol)
3 fatty acid attached to 1 glycerol linked by condensation reactions to form an ester bond (3 ester bonds in 1 triglyceride)
COOH=carboxylic acid group.
Water is released.
Saturated - containing the maximum number of hydrogen atoms (long straight chains), They pack together closely so they have strong intermolecular forces, which makes the fat solid at room temperature.
Unsaturated- monounsaturated (1 double bond for every fatty acid chain) polyunsaturated (larger number of double bonds for each fatty acid chain.
Double bonds cause kinks preventing unsaturated chains from joining together so they have weaker intermolecular forces which result in oils that are liquid at room temperature.
Cholesterol is a type of short chain lipid. It's vital in all membranes for organisations and functions.
Helps to produce sex hormones like testosterone and progesterone.
Made in the liver from saturated dats, also obtained through diet.
Phospholipids are like triglycerides but have a phosphate head (negatively charged)instead of a fatty acid chain.
Fats provide essential fatty acids the body can't synthesise (vitamins A,D,E,K)
The energy balance
DRVs (dietary reference values) are estimates of requirements not goals. Provides a range of values in which a healthy balanced diet should fall.
HRNIs (higher reference nutrient intake)
LRNIs (lower reference nutrient intake)
EAR (estimated average requirement)
Energy input=energy use = normal weight
Energy input greater + Energy use lower = overweight (positive energy balance)
Energy input lower + Enery use greater = underweight (negative energy balance)
A constant supply of energy is needed to perform bodily functions like temperature regulation and breathing. This energy is called basal metabolic rate (BMI) and varies between individuals.
Body mass index (BMI) /waist to hip ratio
Body mass (kg)/height^2(m^2) e.g. 65kg/1.72m^2= 22
Not necessarily an accurate measure for athletes, people over 60, or those wiht long term heart conditions.
Waist to hip ratio has strong correlation with heart attacks (waist circumfrence/hip circumfrence)
Men - 0.9 women- 0.85
Obesity increases the risk of type 2 diabetes (non insulin dependent) which increases the risk of heart diseases and strokes. It can cause high blood pressure and elevated lipid levels.
Evidence shows a positive correlation between blood cholesterol levels and coronary heart disease
Cholesterol isn't soluble in water so for it to be transported it combines with proteins to form lipoproteins.
LDLs Low density lipoproteins: main cholesterol carrier in the blood. Saturated triglycerides + protein + cholesterol. They bind to receptor sites on cell membranes excess LDLs overload these receptors so there is high blood cholesterol levels that can be deposited in artery walls forming atheromas.
HDLs High density lipoproteins: Higher percentage of protein. Unsaturated triglycerides+cholesterol+proteins. They transport cholesterol to the liver to be broken down which lowers blood cholesterol levels and helps remove fatty plaques.
Haemoglobin carries carbon monoxide instead of oxygen so less oxygen is reaching the cells . When arteries narrow blood supply further there is even less oxygen reaching the cells which results in an increased heart rate .
Nicotine stimulates the production of adrenaline which causes blood vessels to constrict which increases blood pressure.
Carcinogens can cause endothelial damage.
It reduces HDL levels.
Exercise maintains a healthy weight, reduces the risk of obesity and hence the development of tye 2 diabetes , increases HDL levels without affecting LDLs.
An active person is more likely to survive a heart attack or stroke.
Heredity and risk/apolipoproteins
Heredity and risk
Some single gene disorders increase early development of CHD.
FH (familial hypercholesterolaemia) leads to mutations in the LDLR gene which causes LDL receptors to not form or to be defective which results in high blood LDL levels.
Apolipoproteins (protein component of lipoproteins, formed in the liver and intestines, helps stabilise lipoprotein structure)
This cluster is associated with CHD and other diseases (alzheimers).
Multifactorial : heredity, physical environment, social environment and lifestyle behaviour all contribute to risk.
APOA: found in HDLs, takes cholesterol to liver for excretion,mutations cause low level of HDLs and hence less remmoval of choesterol.
APOB: found in LDLs , cholesterol from blood to cells, mutations cause high LDL levels.
APOE: found in LDLs and VLDLs, 3 alleles (E2,E3,E4) APOE4 slows cholesterol removal.
Unstable radicles occur when an atom han an unpaired electron.
They are highly reactive and can damage cell components (genetic material and enzymes).
This damage is associated with heart disease and premature aging.
Vitamin C offers protection against radical damage, it provides hydrogen atoms which stabilise the radical bby pairing up wiht its unpaired electron.
Adult should have no more than 6 grams.
Sodium value rather than salt value is given ( actual salt value is 2.5X greater)
Causes the kidneys to retain water, increasing blood fluid levels, causing elevated blood pressure and increasing the risk of CVD.
Releases adrenaline causing constriction , causing raised blood pressure.
Leads to obesity through overeating, a poor diet, and higher alohol consumption.
Causes obesity, raises blood pressure,irregular heartbeat.
Has protective properties (moderate consumption)
Can result in tissue damage.
Can damage liver, brain and heart.
Liver: detoxification and processing carbohydrates, proteins and fats.
Alcohol provides ethanal (3 carbon carbohydrate) which could end up in VLDLs increasing risk of plaque deposition.
Wine is associated with high HDL levels.
Reducing the risk of cardiovascular disease
Stop smoking, maintain blood pressure less than 145/85 mmHg , maintain low blood cholesterol, maintain normal BMI,do more physical exercise and consume moderate/no alcohol.
Controlling blood pressure: ACE inhibitors (angiotensin coverting enzyme) Reduces the synthesis of angiotensin 2 which causes vasoconstriction. Inhibitor prevents more being produced from inactive form- angiotensin 1, which reduces vasoconstriction and lowers blood pressure. Dry cough, irregular heart beat,dizziness, reduces risk of kidney failure.
Calcium channel blockers:Blocks calcium channels in muscle cells in artery lining. Calcium must pass through channel for muscle contraction. Failure of calcium to reach muscles means vessels don't constrict so blood pressure is lowered. Headaches,dizziness,irregular heart beat, can worsen symptoms of heart failure.
Diuretics: Increase volume of urine produced by the kidneys . Lowers blood plasma volume and cardiac output which lowers blood pressure.
Usual combination of antihypertensives = ACE inhibitor + ?
Anti coagulent and platelet inhibitory drug treatm
Prevents the formation of a blood clot in an artery.
Reduces platelet aggregation and clotting.
Aspirin reduces stickiness of platelets.
Warfarin : affects the synthesis of clotting factors.
Risks include internal bleeding.
Statins inhinit the enzyme involved in the production of LDLs
Linear relationship between LDL reduction and reductions in incidences of CHD.
Reduced saturated fat
More polyunsaturated fats
Functional foods wiht sterols and stanols which compete wiht cholesterol during its absorption in the intestines (margarines)
More non starch polysaccharides (pectins, guar gum)They form a gel that prevents cholesterol absorption.
Oily fish (omega 3) - polyunsaturated , vital for cells to function,reduces heart disease and joint inflammation.