Topic 1: sub 2- Circulation and Health Flashcards
formula for area:
length x height x sides
formula for volume:
length x width x height
why we need a transport system:
-diffusion in single-celled organisms can occur directly between the external environment and the cell, this is known as simple diffusion as it occurs only through the cell membrane
-exchange of substances, such as oxygen for these organisms occurs very quickly as they have a very large surface area: volume ratio
-for larger organisms, like us humans, we have low surface area: volume ratio, meaning diffusion would be too slow to supply all cells with the nutrients they need and this is why larger organisms have mass transport systems that supply all cells with vital substances
circulatory system:
-the mammalian circulatory system is comprised of the heart and three types of blood vessels: arteries, veins and capillaries
-each blood vessel is adapted to its role in the circulation of the blood
arteries:
-arteries carry oxygenated blood away from the heart
-this vessel has thick walls containing muscles and elastic that expand and recoil with each heartbeat to withstand the high pressure of the blood
-they have a relatively small lumen (hole in the centre through which the blood passes)
-arteries contain no valves
-its inner lining is folded to allow it to stretch
-arteries split into smaller blood vessels called arterioles which split into capillaries
-they are lined with smooth endothelium to reduce friction and ease flow of blood
capillaries:
-arterioles branch into these to supply cells with substances from the blood
-they are numerous and highly branched so have a large surface area
-their walls are one cell thick to allow quick diffusion
-very narrow diameter to reach close to every cell
veins:
-capillaries join back up to form these, so veins carry deoxygenated blood back to the heart
-carry blood a low pressure to have thin walls
-have a wide lumen to maximise blood flow to the heart
-have valves to prevent backflow (blood flowing in the wrong direction)
structure of the heart:
-the heart is comprised of 4 chambers: the left and right atria and the left and right ventricles
-the atria receive blood into the heart from the veins
-the ventricles pump blood out of the heart via the arteries to the lungs or the body
-between the ventricles and the atria are the atrioventricular valves which prevent blood flowing back from the ventricles and into the atria; between the ventricles and the arteries leaving the heart are the semilunar valves which prevent backflow of blood from the arteries into the ventricles
a double circulatory system:
-mammals are described as having a ‘double circulatory system’, this is because the blood flows through the heart twice in each circulation
-blood first enters the heart into the right atrium through the largest vein in the body- vena cava
-the first time it leaves the heart it travels from the right ventricle via the pulmonary artery to the lungs where it becomes oxygenated, the blood then returns to the heart via the pulmonary vein into the left atrium
-the second time the blood leaves the heart is from the left ventricle via the aorta, where blood now flows to the rest of the body
the cardiac cycle:
-the movement of blood through the heart is carefully controlled by the contracting and relaxing of heart muscles, the cardiac cycle has three stages as follows:
1. Atrial systole
2. Ventricular systole
3. Cardiac diastole
the cardiac cycle: atrial systole
-the atria contract and this forces the atrio-ventricular valves open and blood flows out of the atria and into the ventricles
-pressure in the atria is greater than in the ventricles, so blood is forced out
the cardiac cycle: ventricular systole
-the ventricles then contract, causing the atrio-ventricular valve to open and close and semi-lunar valves to open
-thus allowing blood to leave the left ventricle through the aorta and right ventricle through the pulmonary artery
the cardiac cycle: cardiac diastole
-the atria and ventricles relax, elastic recoil of the heart lowers the pressure inside the heart chambers and blood is drawn from the arteries and veins
-thus causing semilunar valves in the aorta and pulmonary arteries to close, preventing backflow of blood
transport of gases in the blood: haemoglobin
-haemoglobin is a water soluble globular proteins found in red blood cells, which consists of two beta polypeptide chains, 2 alpha polypeptide chains and 4 haem groups
-each of the 4 polypeptide chains is bound to a haem group (Fe2+) to which 1 oxygen molecule can bind
-this means each molecule of haemoglobin can carry 4 oxygen molecules
-the oxygen binds with haemoglobin to form oxyhaemoglobin, and can unbind when needed in respiring cells and tissues
transport of oxygen and carbon dioxide:
-the affinity of oxygen for haemoglobin (how easily oxygen loafs onto haemoglobin) varies depending on the partial pressure of oxygen, which is a measure of oxygen concentration
-therefore, as partial pressure increases, the affinity of Hb for oxygen increases
-this means that oxygen binds to Hb more readily
-this occurs in the lungs in the process known as loading
-during respiration, oxygen is used up therefore the partial pressure decreases, decreasing the affinity of oxygen for Hb
-as a result of that, oxygen is released from Hb in respiring tissues where it is needed; this is known as unloading
-as oxygen diffuses into respiring tissues for respiration, carbon dioxide diffuses out and into the capillaries
-here, the low partial pressure of oxygen environment, carbon dioxide binds to Hb to form carboxyhaemoglobin
-the deoxygenated blood returns to the lungs where carbon dioxide unloads from Hb, which binds to oxygen again
dissociation curves:
-dissociation curves illustrate the change in haemoglobin saturation as partial pressure changes
-the saturation of haemoglobin is affected by its affinity for oxygen, therefore in the case where partial pressure is high, Hb has high affinity for oxygen and is therefore highly saturated, and vice versa
factors resulting in different affinities: saturation
-saturation can also have an effect on affinity, as after binding to the first oxygen molecule, the affinity of Hb for oxygen increases due to a change in shape, this making it easier for the other oxygen molecules to bind
factors resulting in different affinities: fetal haemoglobin
-the haemoglobin present in foetuses has a different affinity for oxygen compared to adult haemoglobin, as it needs to be better at absorbing oxygen because by the time oxygen reaches the placenta, the oxygen saturation of the blood has decreased
-therefore, fetal haemoglobin must have a higher affinity for oxygen in order for the foetus to survive at low partial pressure
factors resulting in different affinities: the Bohr effect
-the affinity of Hb for oxygen is also affected by the partial pressure of carbon dioxide
-carbon dioxide is released by respiring cells, which require oxygen for the process to occur
-therefore, in the presence of carbon dioxide, the affinity of haemoglobin for oxygen decreases, thus causing it to be released
astherosclerosis:
-astherosclerosis is the hardening of arteries cause by the build up of fibrous plaque called an atheroma
-atheroma formation is the cause of many cardiovascular diseases and occurs as following:
1. The endothelium which lines the arteries is damaged, for instance by high cholesterol levels, smoking or high blood pressure
2. This increases the risk of blood clotting in the artery and leads to an inflammatory response causing white blood cells to move into the artery
3. Over time, white blood cell, cholesterol, calcium salts and fibres build up and harden leading to a plaque formation
4. The build up of fibrous plaque leads to narrowing of the artery and restricts blood flow thus increasing the blood pressure which in turn damages the endothelial lining and the process is repeated
blood clotting:
-blood clots are formed to minimise blood loss from damaged vessels, and also to prevent pathogens entering the bloodstream
-blood clots are important to preventing damage to the body, however when they form on the inside of blood vessels, they can restrict blood flow through the vessels and cause a blockade
-this is known as thrombosis and can cause cardiovascular disease, blood clots are formed as follows:
1. Platelets come into contact with a damaged blood vessel wall and change shape from flattened discs to spherical shapes with thin outward projections which form a temporary plug by clumping together
2. The platelets and damaged tissues release clotting factors such as thromboplastin which causes prothrombin to change to thrombin
3. This enzyme catalyses the conversion of fibrinogen to insoluble fibrin, whose strands form a mesh, trapping bundles of blood cells, more platelets attach to this, forming the clot
the effects of astherosclerosis on health: aneurysms
-weakened artery walls
-bulging of artery wall (may rupture)
-commonly occurs in the aorta
-potentially life-threatening if ruptured
the effects of astherosclerosis on health: raised blood pressure (hypertension)
-narrowed arteries restrict blood flow
-increased resistance to blood flow
-heart must work harder
-risk factor for other cardiovascular events (heart attacks, strokes)
the effects of astherosclerosis on health: heart disease
-Angina:
-reduces blood flow to the heart
-chest pain (especially during exertion)
-temporary, typically relieved by rest
-Myocardial infarction (heart attack):
-complete blockage of coronary artery
-heart muscle deprived of oxygen
-permanent damage to heart tissue if not treated quickly
-symptoms include sever chest pain, shortness of breath, sweating
