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biology AS level edexcel SNAB 1.1 lifestyle health and risk : what is cardiovascular disease?
Transcript of biology AS level edexcel SNAB 1.1 lifestyle health and risk : what is cardiovascular disease?
Polarisation of water
coronary arteries supply the heart muscle with blood.
types of closed circulatory systems
single circulatory systems
limitations of diffusion
-requires a large surface area to volume ratio
Multi-cellular organisms need a circulatory system in order to overcome the limitations of diffusion.
Circulatory systems use mass flow to meet the requirements for an organism and maintain a steep concentration gradient for transport of substances around the body.
earthworms have 3 hearts to give blood a "boost" to keep it flowing around the body.
frogs have a 3 chambered heart where oxygenated and deoxygenated blood mix in the central chamber.
open circulatory systems
blood flows into body cavities and diffuses into cells.
most insects have an open circulatory system
closed circulatory systems
these are commonly found in vertebrates.
-the heart pumps blood to the lungs or gills
-blood leaving the lungs flows around the body then back to the heart
-fish have a single circulatory system
-low pressure to protect the delicate tissue in the lungs
-slow rate of flow is overcome by very wide blood vessels
double circulatory systems
-oxygenated and deoxygenated blood are kept seperate within the heart resulting in efficient gas exchange.
-all birds and mammals have a double circulation
-blood flows through the heart twice per circuit.
-blood can be pumped at 2 different pressures; low pressure for the pulmonary circuit and high pressure for the systemic circuit
Water molecules are polar molecules because the hydrogen atoms on one side of the molecule are delta positive and and the oxygen has a delta negative charge.
Polar charges are very small compared to the charges on ions.
The delta positive and delta negative charges attract forming a hydrogen bond so many water molecules can link together in a network of simple molecules.
hydrogen bonds are very weak compared to the covalent bonds between atoms in the water molecules.
The partial charges are due to the covalent bond between the atoms being slightly closer to the oxygen than the hydrogen atom.
Polarisation explains all of water's unusual properties
-high specific heat capacity
-high boiling point; CO2 is a similairly sized molecule but has a far lower boiling point
-high surface tension due to the water molecules linking together.
-water is a good solvent
these all make water an ideal transport medium
water as a solvent
ions in solution are surrounded by the water molecules polar ends.
The superior vena cava takes deoxygenated blood from the upper body to the heart.
Semilunar valves stop backflow of blood back into the ventricles from the arteries. their name comes from the fact that they are the shape of a crescent moon.
The atrioventricular valves stop backflow of blood into the atria from the ventricles. the tricuspid valve is on the right side and is made of 3 parts.
the atria are the top chambers in the heart.
the inferior vena cava brings deoxygenated blood from the lower body to the heart.
the pulmonary artery brings deoxygenated blood to the lungs.
the septum divides the 2 sides of the heart.
the ventricles are the lower chambers of the heart. the left ventricle is the largest chamber as it has to pump blood all around the body.
the mitrial valve is also called the bicuspid valve and is another atrioventricular valve.
the pulmonary veins bring oxygenated blood from the lungs to the heart.
the aorta is the largest artery and brings oxygenated blood all around the body at a very high pressure.
arteries and veins
-carry blood away from the heart at high pressure
-have thick walls to withstand the high pressure
-have a narrow lumen to maintain the high pressure
-contain lots of elastic fibres to prevent vessel damage and maintain smooth blood flow.
-contain a lot of collagen to prevent overstretching and provide elastic recoil.
-smooth walls to maintain blood flow
-walls are lined with endothelial tissue to minimise resistance.
-high proportion of collagen to muscle fibre to prevent overstretching
-smooth endothelial lining to reduce resistance
-valves to prevent backflow of blood during diastole
-carry blood to the heart
-have a thin layer of muscle fibre
-are used to exchange materials with the body's cells
-they are small and only a few cells thick for efficient diffusion
-they form a highly branched network to provide a large surface area.
-narrow lumen with spaces between cells
-no muscle tissue or elastic fibres
-made of squamous epithelial cells
arterioles control blood flow to the capillaries. they slow down the high pressure blood from the arteries to protect the capillaries and allow time for exchange.
Venules are small blood vessels that link veins to capillaries.
The cardiac cycle
The myocardium (heart muscle) contracts to create pressure and maintain blood flow.
Systole - heart contraction
Diastole - heart relaxation
Cardiac cycle - the sequence of the heart pumping blood
ventricles fills with blood
atrioventricular valves close
semi lunar valves open
blood is pumped through the aorta
atrioventricular valves open
semi lunar valves close
atria start to fill
This is a continuous cycle and happens simultaneously for both sides of the heart.
This can be represented on a pressure graph where lines crossing mean valves opening or closing.
atherosclerosis is the blocking of an artery. an occlusion is the blockage of any blood vessel
endothelium is damaged due to toxins or high blood pressure
the artery wall hardens and loses elasticity
an atheroma forms
calcium salts and fibrous tissue are attracted to the atheroma
blood vessel narrows
this swells and hardens forming a plaque
The mass of cells causes the accumulation of cholesterol and other products of digestion.
white blood cells enter the wound
blood pressure rises