4.3 - circulation Flashcards
what are the 4 features do all mass transport systems have
-a system of vessels which carry the transport medium
-a transport medium which carries all the substances needed to be delivered to cells and and waste products needed to be removed from cells
-a way of making sure that substances are moved in the right direction
-a means of moving substances fast enough to supply the needs of an organism
describe a double circulatory system
-includes the systematic circulation where oxygenated blood is transported from the heart to the body
-here O2 diffuses into cells, and CO2 diffuses into the blood
-deoxygenated blood is transported from the body to the heart
-the the pulmonary circulation carries deoxygenated blood from the heart to the lungs to be oxygenated
-then oxygenated blood is transported from the lungs to the heart
what are the advantages of a double circulatory system
-makes sure that the oxygenated and deoxygentated blood don’t mix together, so that the maximum amount of oxygen is able to diffuse into cells
-allows blood in different parts of the body to be at different pressures
e.g. blood going through blood vessels in the lungs are at a lower pressure so it doesn’t damage blood vessels and enough time is allowed for O2 to diffuse in and CO2 out
if this low pressure blood was transported to the body blood would move too slowly
-because oxygenated blood from the lungs returns back to the heart, blood can be pumped again and transported around the body
describe what is meant by a single circulatory system
-the heart pumps blood to the gas exchange organs and then travels around the body, then returns back to the heart
describe the circulatory system in fish
-single circulatory system
-deoxygenated blood is pumped from the heart to the capillaries in the lamellae of the gills where oxygen diffuses into the blood
-oxygenated blood is transported from the lamellae to the systematic capillaries in the body where oxygen diffuses out the blood into cells
-deoxygenated blood returns to the heart
why can fish survive with a single circulatory system
-they have a lower energy requirement so need to carry out less respiration
-they don’t need to maintain internal body temperature
what are the advantages and disadvantages of the single circulatory system in fish
advantage:
-after blood flows through the gills it is fully oxygenated, so when this blood flows through the body there is a high concentration gradient for increased rate of diffusion
disadvantage:
-when blood passes through the capillaries in the lamellae it loses a lot of pressure so the circulation of blood to the rest of the body is slow, limiting the rate of oxygen delivery
describe the circulatory system of insects
-open circulatory system, blood is not contained in blood vessels, it circulates through the body cavity
-the transport medium is haemolymph, blood and lymph are mixed together
-the dorsal muscular pumping organ pumps heamolymph around the body cavity
-this circulatory system transports amino acids, carbohydrates and hormones, it doesn’t transport oxygen efficiently
-so insects rely on their gas exchange system for respiration
name the components of blood
-plasma
-platelets
-leukocytes
-erythrocytes
describe the roles of the plasma
-the plasma transports:
-digested food products (amino acids + glucose) from the small intestines to parts of the body for immediate use or storage
-nutrient molecules from storage areas to cells
-excretory products (CO2 + urea) from cells to organs (lungs + kidneys) that excrete them from the body
-hormones
-plasma helps to maintain a constant body temperature by transferring heat around the body
describe the role of the erythrocytes
-oxygen binds to haemogobin
-so erythrocytes transport oxygen from the lungs to cells
where are erythrocytes formed
the bone marrow
explain how erythrocytes are adapted to their function
-biconcave disc shape, high surface area to volume ratio, to increase the rate that O2 diffuses in and out of the erythrocytes
-no nucleus, more room for more haemoglobin to increase the amount of O2 they can carry
-haemoglobin carries a small amount of CO2 produced in respiration to be transported back to the lungs
are erythrocytes or leukocytes larger
leukocytes are larger
they can still be transported through small blood vessels because they can change shape
where are leukocytes formed
in the bone marrow
but some leukocytes mature in the thymus gland
where are platelets formed and what are they
in the bone marrow
they are tiny fragments made from megakaryocytes
what is the function of the arteries
-carry blood away from the heart to cells
-carry oxygenated blood (except from the pulmonary artery and the umbilical artery)
what are the arterioles
the arteries leaving the heart branch off in every direction
the diameter of the lumen gets smaller the further away the artery is from the heart
the very smallest arteries of the arterial system and furthest from the heart are the arterioles
what 2 arteries carry deoxygenated blood
-pulmonary artery, carries deoxygenated blood from the heart to the lungs
-umbilical artery carries deoxygenated blood from fetus to the placenta
what is the structure of the arteries
-external layer of tough tissue
-middle layer contains smooth muscle and elastic fibres
-elastic fibers allow the artery to stretch to withstand a greater volume of blood without being damaged
-smooth muscle can contract or relax to change the size of the lumen, controlling blood flow
-arteries nearest the heart have more elastic fibres and arteries furthest from the heart have a greater proportion of muscle tissue
-smooth lining lines the lumen, allows for the easiest flow of blood
-lumen, where blood flows through, small when the artery is unstretched
what is the function of capillaries
-they link arterioles and venules
-their small diameter slows the flow of oxygenated blood, so oxygen and nutrients can diffuse into cells
-CO2 and waste products diffuse into the blood in capillaries
-every cell is close to a capillary
what is the structure of capillaries
-thin walls (1 epithelial cell thick), helps capillaries to fit in between cells and increase rate of diffusion
-lumen is only large enough to fit 1 erythrocyte at a time, slows down the flow of blood to increase rate of diffusion
what is the function of the veins
-transports blood back to the heart
-carries deoxygenated blood (except pulmonary vein and umbilical vein
what is the structure of the veins
-the capillaries branch into tiny venules, which become larger veins as they get closer to the heart
-tough outer layer made of collagen fibres
-thin layer of smooth muscle and few elastic fibrers
-smooth inner lining
-relatively large lumen
what 2 veins don’t carry deoxygenated blood
-the pulmonary vein carries oxygenated blood from the lungs into the heart
-the umbilical vein carries oxygenated blood from the placenta to the fetus
what 2 veins carry deoxygenated blood into the heart
-superior vena cava, carries blood from the upper parts of the body
-inferior vena cava carries blood from lower parts of the body
at any time which blood vessel holds the highest volume of blood
veins
explain why the blood in veins is at low pressure
-when the heart muscle contracts pressure surges in blood can be seen in arteries
-but after blood passes through the capillaries pressure surges are eliminated
explain how veins return low pressure blood to the heart
-semi-lunar valves
-though out the venous system there are one-way valves
-these are infoldings of the vein inner wall
-blood can pass through the valves, but if blood flows backwards the valves close, preventing the backflow of blood
-large veins are situated in between large muscles
-during physical activity muscles contract, which squeezes veins, opening the valves and pushing blood through
what muscle makes up the heart
cardiac muscle
how is cardiac muscle different to other types of muscle
-it can carry on contracting without getting fatigued
-contains lots of myoglobin, which stored oxygen needed for respiration
-good blood supply through the coronary arteries, which bring oxygenated blood to the cardiac muscle
-myogenic
what is atrial systole
when the atria contract together forcing blood into the ventricles
what is ventricular systole
when the ventricles contract forcing blood out of the ventricles into the pulmonary artery and aorta
happens 0.13 seconds after atrial systole
what is diastole
between systole the heart relaxes and fills with blood
there is atrial diastole and ventricular diastole
when there is atrial systole there is ventricular diastole
when there is ventricular systole there is atrial diastole
what does myogenic mean and what can be described as myogenic
the heart beat is myogenic in that the cardiac muscle can contract without any stimulus from the nervous system
what does an ECG measure
the electrical changes on the surface of the heart
caused by waves of depolarisation
what is bradycardia
when the heart rate drops below 60 beats per minute
(60 bpm is the intrinsic rhythm)
what is tachycardia
when the heart rate is over 100 beats per minute
may be caused by short term effects like fear and exercise
long term tachycardia is caused by health problems
what is an ectopic heartbeat
-a heart beat that is not a part of the heart’s usual rhythm
-appears on an ECG
why do atheromas develop in the arteries and not in the veins
-blood in the arteries is at higher pressure
-so the endothelium is under more strain and can cause small areas of damage
explain how an atheroma is formed
-damage to the endothelium caused by high blood pressure
-inflammatory response and arrival of macrophages (white blood cells)
-deposits of LDL cholesterol and calcium
-a hardened plaque forms on the endothelium, causing this area of the artery to harden too, so the artery is less elastic than it should be
why does the presence of an atheroma lead to atherosclerosis
-the atheroma means the lumen is much narrower
-increasing blood pressure
-making it harder to transport blood around the body
-high blood pressure makes damage to other areas of the endothelium more likely
how are aneurysms formed
-an artery is narrowed by an atheroma
-blood builds up behind the blockage creating a bulge
-the endothelium is under more pressure than normal, so is weakened
-this is an aneurysm
-if the endothelium splits open it can cause internal bleeding which is fatal
-if the aneurysm is diagnosed before the artery wall splits, surgery can be used to save the patient
explain how atherosclerosis can lead to kidney damage
-the atheroma causes arteries to narrow, raising blood pressure
-high pressure damages blood vessels which filter out urea from the blood
-the high pressure can also force out protein from the blood
explain how atherosclerosis can lead to blindness
-the atheroma causes arteries to narrow, raising blood pressure
-high blood pressure damages the blood vessels supplying the retina
-if these blood vessels are blocked or leak retinal cells are starved of O2
-they die and cause blindness
explain how atherosclerosis can lead to angina
-an atheroma forms in the coronary arteries
-narrowed coronary arteries restricts blood flow to cardiac muscle cells
-so sufficient oxygen isn’t delivered to cells for aerobic respiration
-the cardiac muscle resorts to anaerobic respiration which produces lactic acid
-causing a gripping pain in the chest that can extend to the left arm and jaw
-this is most common during exercise when the cardiac muscle requires more oxygen for a higher rate of respiration to produce ATP
what advice is given by doctors to patients diagnosed with atherosclerosis
-lose weight by doing regular exercise
-eat a balanced diet low in saturated fat
-don’t smoke
what medical treatment are given to patients diagnosed with atherosclerosis
-stent
-heart bypass surgery
-drugs which cause the rapid dilation of the coronary arteries
what is another name for a heart attack
myocardial infarction
explain what causes myocardial infarction
-when one of the branches of the coronary arteries becomes completely blocked off so part of the heart in permanently starved of oxygen
-the main cause of this is thrombosis (blood clot)
-if thrombosis occurs towards the bottom of the heart it can cause a small heart attack, if towards the top a large heart attack that can develop into cardiac arrest
-a symptom of myocardial infarction is chest pain which can extend to the left arm and jaw
-pain may last for several hours
-exercise may trigger it or can happen unexpectedly
-death may happen very rapidly or after a few days of symptoms
explain what causes a stroke
-thrombosis or atherosclerosis mean that oxygenated blood isn’t transported to the brain for respiration
-the severity of the stroke depends on whether the blockage is in a main artery supplying the brain with oxygenated blood or a small arteriole
-symptoms include paralysis down one side of the body, loss of vision in 1 eye, confusion
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explain the 3 non-modifiable risk factors for atherosclerosis
genes - there is a genetic tendency in some families/ethnic groups to develop atherosclerosis due to the arteries being more easily damages or cholesterol metabolism may be faulty etc
age - as people get older the arteries lose their elasticity and narrow
sex - under the age of 50 men are more likely to develop atherosclerosis because oestrogen in women reduces the build up of plaque
state the modifiable risk factors for atherosclerosis
-smoking
-diet
-stress
-weight
-lack of physical activity
-high blood pressure
how is weight a risk factor for atherosclerosis
-being overweight doesn’t directly affect the risk of developing atherosclerosis
-but it is an important factor of risk because other factors that are direct result of being overweight do increase risk of atherosclerosis
-including type 2 diabetes and high blood pressure
how does type 2 diabetes increase the risk of atherosclerosis
can damage endotherlium
how does stress increase the risk of atherosclerosis
-stress causes the release of cytokines
-which trigger an inflammotory response in blood vessels
-leading to plaque formation
-stress can also raise blood pressure
what are the functions of blood clots
-prevents the loss of blood which can be fatal
-prevents pathogens entering the body and causing disease
what is the function of serotonin
-a hormone
-causes the smooth muscle of blood vessels to contract, which narrows blood vessels, cutting off blood flow to damages areas
what is the function of thromboplastin
-an enzyme
-initiates the blood clotting cascade
explain the blood clotting cascade
-damaged tissue exposes collagen fibres
-the contact between platelets and collagen fibres causes platelets to break open to release thromboplastin
-thromboplastin catalyses the conversion of prothrombin (soluble enzyme) into thrombin (soluble enzyme), this happens in the presence of calcium ions
-thrombin catalyses the conversion of fibrinogen (soluble protein) into fibrin (insoluble protein)
-fibrin forms a mesh of fibres to cover the wound
-platelets and blood cells get trapped in the fibrin mesh to form the blood clot
-proteins in the platelets contract, making the clot tighter and tougher to form a scab
what is tissue fluid
-cells which make up the capillary walls aren’t directly touching each other, there is space between each cell
-making the capillary walls very permeable
-this space isn’t large enough for erythrocytes or plasma proteins to pass through
-a fluid that is plasma containing leukocytes and other components of the blood moves out of the capillaries and bathes the individual cells of the body
what is the definition of oncotic pressure
the tendency for water to move into the capillaries by osmosis
explain oncotic pressure in terms of tissue fluid
-the blood in capillaries has a low water potential
-because plasma proteins in the blood exert an osmotic effect
-the tissue fluid surrounding the capillaries has a higher water potential
-because water moves from an area of high to low water potential, the tendency is for water to move into the capillaries by osmosis
-the pressure behind this movement is oncotic pressure
what is hydrostatic pressure in terms of tissue fluid
-it is the left over pressure from the heartbeat that remains as the blood enters the arterial end of the capillary bed
-this hydrostatic pressure forces tissue fluid out through the capillary walls
explain the movement of tissue fluid as blood flows from the arteriole end of the capillary bed into the capillaries
-as blood flows from the arterioles into the capillary bed
-the hydrostatic pressure foring fluid out is relatively high
-the oncotic pressure tending to force water into the capillaries is fairly constant
-the hydrostatic pressure is higher than the oncotic pressure
-so fluid is squeezed out of the capillaries and fills the space around all body cells
-diffusion between cells and the tissue fluid take place
explain the movement of tissue fluid as blood flows from the capillaries into the venule end of the capillary bed
-as blood flows from the arterioles into the capillary bed
-hydrostatic pressure falls to be relatively low
-because the pressure from the heartbeat is completely gone
-and some fluid moves out of the capillaries to form tissue fluid, so volume of blood in the capillaries is lowered
-oncotic pressure of the blood is still constant due to the constant presence of large plasma proteins
-the oncotic pressure exerted by water moving into the capillaries is greater than the hydrostatic pressure
-water returns to the capillaries by osmosis
-once blood enters the venules most of the tissue fluid has returned to the blood vessels
what happens to tissue fluid when hydrostatic pressure is greater than oncotic pressure
fluid moves out of the capillaries forming tissue fluid
what happens to tissue fluid when oncotic pressure is greater than hydrostatic pressure
water moves into the capillaries and tissue fluid is lost
explain how lymph is formed
-90% of tissue fluid returns to blood vessels but 10% doesn’t
-this 10% of tissue fluid drains into lymph capillaries and becomes lymph
-lymph has fewer nutrients and less oxygen than tissue fluid as these have been taken up by cells
-lymph may have a high level of fatty acids because they can be absorbed directly into the lymphatic system in the villi of the small intestine
-lymph capillaries join up to make bigger lymph vessels
-lymph vessels are similar to veins because they have valves which prevent the backflow of lymph
-and contractions of body muscles as we move, move the lymph
-lymph is returned to the blood in the neck where it joins the left and right subclavian veins
explain the role of lymph glands in the immune system
-lymphocytes accumilate in the lymph glands to produce antibodies
-produced antibodies are carried by the lymph and empties into the blood at the subclavian veins
-lymph glands remove bacteria and other pathogens to be destroyed by phagocytes
-if a patient has enlarged lymph glands they are fighting an infection
explain what is meant by haemoglobin has positive cooperativity
-the 1st oxygen molecule that binds to haemoglobin alters the arrangement of molecules making it easier and easier for the following O2 molecules to bind
-after the 1st oxygen molecule dissociates with heamoglobin it is harder and harder for the rest of the O2 molecules to dissociate
explain how a concentration gradient in maintained even though oxygen is binding to erythrocytes
-the oxygen concentration of erythrocytes entering the lungs is relatively low
-oxygen is picked up and bound to heamoglobin so the free O2 concentration of the cytoplasm of erythrocytes stays low
-the steep concentration gradient between air in the lungs to erythrocytes allows more and more O2 to diffuse
explain how oxygen travels from erythrocytes into respiring body cells
-O2 concentration in body tissue is relatively low
-O2 concentration in the cytoplasm of erythrocytes is higher than that of the surrounding tissue
-so O2 diffuses into body cells
-some oxyhaemoglobin molecules dissociate to release some O2 molecules which diffuse into body tissue
-when resting only 25% of oxygen carried by oxyhaemoglobin is released into body cells
what are the 3 ways carbon dioxide is transported in the body
-some CO2 dissolves into the plasma
-some CO2 combines with haemoglobin to form carbaminohaemoglobin
-most CO2 is converted into hydrogencarbonate ions
explain how CO2 is transported by being converted into carbaminohaemoglobin
where does this happen
-haemoglobin contains 4 polypeptide chains
-on one end of each polypeptide chain there is a free amino group
-in the respiring tissue there is a high concentration of CO2
-each amino group reacts with 1 CO2 molecule to form carbaminohaemoglobin
-this is a reversible reaction
-in the lungs there is a low concentration of CO2
-carbaminohaemoglobin breaks down releasing CO2
Describe the similarities and differences between the circulatory systems in mammals and insects
Similarities: both have hearts and valves
Differences: insects have an open system, mammals have a closed system with blood vessels
Gas exchange in insects occurs in the tracheal system, in mammals it’s in the pulmonary circulatory system
what is the oxygen dissociation curve for myoglobin not s shaped
-myoglobin’s affinity for oxygen doesn’t change
-because myoglobin doesn’t have cooperative bonding to oxygen
explain how tissue fluid is formed
(1 mark)
high hydrostatic pressure forces plasma (and other components of the blood) out of the arteriole end of the capillaries
explain how tissue fluid is returned to the capillaries
-there is are more proteins than tissue fluid in the blood in the capillaries
-because plasma proteins cannot pass through the capillary wall
-oncotic pressure generated by the plasma proteins is greater than hydrostatic pressure
-so the water potential outside the capillary is greater than inside
-fluid moves into the capillaries
Explain how thrombosis develops
Thrombosis is a clot that forms in the coronary arteries
The presence of an atheroma on the endothelium means the endothelium is hardened
So the endothelium is more likely to suffer cracks or damage
When platelets come into contact with collagen fibres exposed by a damaged blood vessel the blood clotting cascade is triggered
Or the endothelium may become damaged due to high blood pressure or smoking
