Circulatory system Flashcards
Why do we need a mass transport system
All cells need energy - most cells get energy through aerobic respiration.
The raw materials for this are glucose and oxygen so the body has to make sure it can deliver enough of these to all its cells.
In single-celled organisms, these materials can diffuse directly into the cel across the cell membrane. The diffusion rate is quick enough because of the short distance the substances have to travel and have a large surface area: volume ratio.
In mutlicellur organisms, diffusion across the outer membranes would be too slow because the large distance the substances would have to travel to reach all the cells and big organisms have a large S.A:V ratio.
So multicellular organisms have mass transport systems:
1) The mass transport systems are used to carry raw materials from specialised exchange organs ( lungs and the digestive system) to the body cells and remove metabolic waste (co2)
2)In mammals, the mass transport system is in the circulatory system, where blood is used to transport substances around the body.
3)Individuals cells in the tissues and organs get nutrients and oxygen from the blood and dispose of metabolic water into the blood.
How does the heart pumps blood around the body
The heart keeps the blood moving so that substances can get to and from individual cells.
The right side pumps deoxygenated blood to to the lungs and the left side pumps oxygenated blood to the whole body. Features of the heart:
4 chambers: The left ventricle of the heart has thicker, more muscular walls than the right ventricle because it needs to contract powerfully to pump blood all the way round the body. The right ventricle only needs to get blood to the lungs which is nearby.
The ventricles have thicker walls than the atria, because they have to push blood out of the heart whereas the atria needs to push blood into the ventricles.
The atrioventricular valves link the atria to the ventricles and stop blood flowing back into the atria when ventricles contract.
The semilunar valves link the ventricles to the pulmonary artery and aorta and stop blood flowing back into the heart after the ventricles contract.
The cords attach the atrioventricular valves to the ventricles to stop them being forced up in the atria when the ventricles contract.
Function of the valves in the heart
The AV valves link the atria to the ventricle and the SM valves link the ventricles to the pulmonary artery and aorta- they stop blood flowing backwards.
The valves only open one way whether they’re open or closed depends on the relative pressure of the heart chambers.
If theres higher pressure behind a valve its forced to open.
If pressure if higher in front of the valve its forced to shut.
Substances transported through 3 blood vessels
Arteries: CARRY blood FROM the heart to the rest of the body. They’re thick walled, muscular and have elastic tissue in the walls and the endothelium is folded allowing the artery to expand (recoil) to cope with high blood pressure caused by the heartbeat.
Veins: TAKE blood BACK to the heart. They’re wider than arteries with very little elastic or muscle tissue. Veins contain valves to stop the blood flowing backwards. Blood flow though the veins is helped by contractions of the body muscles surrounding them.
Capillaries: are the smallest blood vessels. They are networks of capillaries in tissue (capillary bed) which increase the surface area for exchange between cells and capillaries where metabolic exchange occurs. Capillary walls are one cell thick (endothelium) which speeds up diffusion of substances into and out of cells.
How does the cardiac cycle work
The cardiac cycle is an ongoing sequence of systole (contraction) and diastole (relaxation) of the atria and ventricles that keeps blood continuously circulating round the body. The volume of the atria and ventricles changes as they contract and relax. Pressure changes also occur, due to the changes in the chamber volume (decreeing of the volume of chamber by contraction increases the pressure of a chamber). 3 stages:
1) VENTRICULAR DIASTOLE, ATRIAL SYSTOLE: the ventricles are relaxed. The atria contract, decreasing the volume of the chamber and increasing the pressure inside the chamber. This pushes the blood into the ventricles. Theres a sleigh increase in the ventricular pressure and chamber volume as the ventricles receive the ejected blood from the contracting atria.
2) VENTRICULAR SYSTOLE, ATRIAL DIASTOLE: the atria relax. The ventricles contract (decreasing their volume) increasing their pressure. The pressure becomes higher in the ventricles than the atria, which forces the AV valves to prevent back-flow. The pressure in the ventricles is also higher than in the aorta and pulmonary artery, which forces open the SL valves and blood is forced out these arteries.
3) Ventricular DIASTOLE, ATRIAL DIASTOLE: the ventricles and atria relax: the higher pressure in the pulmonary artery and aorta closes the SL valves to prevent back flow into the ventricles. Blood returns to the heart and the atria fill again due to the higher pressure in the vena cava and pulmonary vein. In turn this starts to increase the pressure of the atria. As the ventricles continue to relax, their pressure falls below the pressure of the atria and so the AV valves open. This allows blood to flow passively (without being pushed by atrial contraction) into the ventricles from the atria. The atria contract and the whole process begins again.
How does atherosclerosis occur
The wall of an artery is made up of several layers and the endothelium is usually smooth and unbroken.
If damage occurs to the endothelium ( high b.p), there will be an inflammatory response- this is where white blood cells (macrophages) move into the area.
The white blood cells and lipids from the blood clump together under the endothelium to form fatty streaks.
Overtime more white blood cells lipids and connective tissue build up and harden to form a fibrous plaque called an atheroma.
This plaque partially blocks the lumen of the artery and restricts blood flow, which causes blood pressure to increase.
The hardening of the arteries caused by atheromas is called atherosclerosis.
How does atheromas increase risk of thrombosis in arteries
atheroma develop within the walls of arteries and can rupture (burst though) the endothelium of an artery damaging the artery wall and leaving a rough surface.
This triggers thrombosis a blood clot forms at the site of the rupture.
This blood clot can cause a complete blockage of the artery or it can become dislodge and black a blood vessel elsewhere in the body.
The blood flow to tissues supplied by the blocked vessel will be restricted so less oxygen will reach those tissues resulting in damage.
Heart attack, stroke, and deep vein thrombosis are there forms of CVC that can be caused by blood clots.
How thrombosis occurs
Thrombosis is used by the body to prevent blood being lost when a blood vessel is damaged. A series of reactions occur that lead to the formation of blood clot.
1)A protein called thromboplastin is released from the damaged blood vessel.
2)Thromboplastin triggers the conversion of prothrombin (soluble protein) into thrombin (enzyme).
3)Thrombin then catalyses the conversion of fibrinogen (soluble protein) to fibrin (solid insoluble fibre)
The fibrin fibres tangle together and form a mesh in which platelets (small fragments of cells in the blood) and red blood cells get trapped this forms a blood clot.
HOW CAN Blood clots cause heart attacks
1) The heart muscle is supplied with blood by the coronary arteries.
2) This blood contains the oxygen needed by heart muscle cells to carry out respiration.
3) If a coronary artery becomes completely blocked by a blood clot an area of the heart muscle will be totally cut off from its blood supply, so it won’t receive any oxygen.
4) This causes a myocardial infarction
5) A heart attack can cause damage and death of the heart muscle
6) Symptoms incluse pain in the chest and upper body, shortness of breath and sweating.
7) If large areas of the heart are affected complete heart failure can occur which is fatal.
What is a stroke
1) A stroke is a rapid loss of brain function, due to a disruption in the blood supply to the brain.
2) This can be caused by a blood clot in an artery leading to the brain, which reduces the amount of blood and therefore oxygen that can reach the brain.
What is deep vein thrombosis
DVT is the formation of a blood clot in a vein deep inside the body usually in the legs
It can be caused by prolonged activity eg. long haul flights and risks increase with age.
What are the Risk Factors of CVD
1) DIET- a diet hgih in saturated fat increases the risk of CVD. This is because blood cholesterol level which increases atheroma formation. Arethormas can lead to the formation of blood clots which can lead to heart attack, stroke or DVT. A diet high in salt also increase the risk of CVD because it increases the risk of high blood pressure
2) HIGH BLOOD PRESSURE- this increases the risk of damage to the artery walls, which increases the risk of arterhoma formation which can lead to CVD. Excessive alcohol consumption, stress and diet can all increase blood pressure.
3) SMOKING- carbon monoxide in cigarette smoke combines with haemoglobin the protein that carries oxygen in the blood) and reduces the amount of oxygen transported in the blood. This reduces the amount of oxygen available to tissues. If the heart muscle doesn’t get enough oxygen it can lead to a heart attack and if the brain doesnt than it can lead to a stroke.
Nicotine- in cigarette makes the platelets sticky, increasing the chance of blood clots forming which increases the risk of CVD.
Smoking also decreases the amount of antioxidants in the blood- these are important for protecting cells from damage. Fewer antioxidants means cell damage in the artery walls is more likely and this can lead to arethoma formation which increases the risk of CVD.
4) INACTIVITY- a lack of exercise increases the risk of CVD because it increases blood pressure.
Factors of CVD beyond your control
Genetics) some people inherit particular ales that make them more likely to have a high blood pressure of high blood cholesterol so they are more likely to suffer from CVD.
Age) the risk of developing CVD increases with age.
Gender) men are three times likely suffer from CVD than pre-menopausal women.
WHY might someones perception of risk be different from actual risk
RISK can be defined as the probability of an unwanted event occurring; E.g if you smoke you increase the chance of developing CVD.
Cholesterol and increase risk of cvd
Cholesterol is a lipid made in the body. Some is needed for the body to function normally. Cholesterol needs to be attached to protein to be moved around, so the body forms Iipoproteins - substances composed of both protein and lipid. There are two types of lipoprotein: HIGH DENSITY LlPOPROTElNS
1) They are mainly protein. 2) They transport cholesterol from body tissues to the liver where it’s recycled or excreted. 3) Their function is to reduce total blood cholesterol when the level is too high
Low density lipoproteins
They are mainly lipid. They transport cholesterol from the liver to the blood, where it circulates until needed by cells. Their function is to increase total blood cholesterol when the level is too low. High total blood cholesterol level (the level of HDL, LDL and other cholesterol) and high LDL level have both been linked to an increased risk of CVD.
