2.3a adaptations for transport in animals Flashcards
what does a closed circulatory system mean?
the blood pumped by the heart is contained within blood vessels
- blood doesn’t come into direct contact with the cells
- red blood cells contain haemoglobin which transport oxygen within the circulatory system
what are some examples of organisms that have a closed circulatory system?
- fish
- earthworms
- mammals
what does an open circulatory system mean?
the blood is not contained within vessels, but moves freely + comes into direct contact with the cells
- blood is called haemolymph
- no red blood cells
- oxygen delivered directly to the tissues by the trachea
- haemolymph found in fluid-filled space around the organs called a haemocoel
what is the blood in an open circulation system called?
haemolymph
and is in the body cavity or haemocoel
what type of organisms have an open circulatory system?
- arthropods
do organisms that have an open circulation system have red blood cells?
no - there are no red blood cells to transport oxygen
- oxygen is delivered directly to the tissues by the tracheae
do organisms that have an open circulation system have a heart?
many animals with an open circulation do have a heart that pumps the haemolytic from one area of the haemocoel to another
- the blood returns to the heart without the aid of blood vessels
closed circulation systems deliver blood (quickly/slowly) to tissues under pressure?
quickly
red blood cells contain haemoglobin which transports oxygen within the circulatory system. what has enabled the evolution of larger size in animals?
the rapidity of transport
what happens in a single circulation?
blood passes through the heart once in each circulation / per complete circuit
e.g fish
what is a disadvantage of single circulation?
the blood loses pressure around the circuit, resulting in slower circulation
what is a double circulation?
when the blood passes through the heart twice in one circulation of the system / per complete circuit)
e.g mammals/humans
the right side of the heart in humans pumps blood to the ____?
lungs for gas exchange
(pulmonary circulation)
the blood returns to the heart and is pumped out to the tissues from the ___ side?
left
systematic circulation
what are some advantages of a double circulation?
- maintains blood pressure around the whole body
- uptake of oxygen is more efficient
- delivery of oxygen and nutrients is more efficient
- blood pressure can differ in pulmonary and systemic circuits
-the blood is repressurised when it leaves the gas exchange surface, giving a faster and more efficient circulation to the tissues
(systemic/pulmonary) circulation takes blood to and from the lungs
pulmonary
_____ circulation takes deoxygenated blood from the heart to the lungs and oxygenated blood back to the heart
pulmonary
_____ circulation takes oxygenated blood to the body tissues and deoxygenated blood back to the heart
systemic
what is the pattern that circulation in both the systemic and pulmonary circuits follow? (through blood vessels)
blood moves from the heart to:
artery —> arteriole —> capillary —> venule —> vein —> back to the heart
Arteries take blood Away from the heart
veINs take blood INto the heart
what are capillaries?
- the site of gas exchange and tissue fluid formation
- the single layer of flattened cells (endothelial cells) which give a small diffusion path
- are a tissue rather than an organ
- capillary beds are extensive and have a massive surface area for diffusion
- form a vast network that penetrates all the tissues and organs of the body
arteries, arterioles, venules and veins are what?
organs of the circulatory system consisting of different tissues
the outermost tissue layer is the ___?
tunica externa
what does tunica externa consist of?
- collagen rich connective tissue; this resits stretching of the blood vessel due to the hydrostatic pressure of the boood
what is the middle tissue layer?
the tunica media
what does the tunica media contain?
- elastic fibres and muscle tissue
- elastic fibres allow the blood vessel to expand to accommodate the blood flow
what is the innermost tissue layer?
a single layer of endothelium cells which provide a smooth surface with little friction and resistance to blood flow
- the endothelium is surrounded by the tunica intima
- blood flows from the heart to arteries
- then to arterioles
- then through a capillary network at the tissues
- which drain into venules
- which drain into veins
- which return blood to the heart
what is the use of the heart?
the heart is a pump that generates pressure
how have arteries been adapted?
to carry blood at high pressures
- they have a thick tunica externa containing collagen fibres, to resist overstretching under pressure
- the layer of muscle and elastic tissue is thick to provide elastic recoil aiding propulsion of blood and maintaining blood pressure
- the lumen of the arteries is relatively small to maintain the pressure of the blood
how are the structure of arterioles different from the structure of arteries?
- arterioles are similar in structure to arteries
- but have more muscle
- this is because they constrict and dilate to control the flow of blood to capillaries
are capillaires an organ?
no they are considered a tissue
why does as blood passes through capillaries, the pressure is lowered? what is this good for?
- bc a capillary bed has a much greater cross sectional area than the arteriole feeding into it
- capillaries are narrow so resistance to blood flow is greater and blood flow slows down
- this is good for gas exchange as the slower flow gives more time for diffusion
- the capillaries have a slightly smaller diameter than a red blood cell, so the red blood cells have to bend to squeeze through
capillaries reduce the pressure of the blood and drain into small veins called?
venules
many venules join larger veins
veins appearence:
- have a large lumen providing little resistance to the blood which is flowing through at low pressure
- the tunica media and externa are far thinner than in arteries as the blood is under much lower pressure and less resistance to pressure is needed
how is blood kept flowing up to the heart from the lower body?
by skeletal muscles squeezing on the veins pushing the blood
how is backflow of the blood prevented?
by valves at intervals along the veins
what is the eyepiece graticule?
it is in the eyepiece of the microscope and is not magnified when the objective lens is altered
- this means that the measurements taken with the eye-piece graticule will change if the objective lens is changed
(you should always calibrate the eyepiece graticule using the objective lens you have made your measurements with)
how is the eyepiece graticule calibrated?
using a stage micromere
(a side and is magnified by the objective lens used)
line up the two scales and count the number of eyepiece units (epu) and the number of stage micrometer units between the two overlaps
e.g 80 epu = same as 20 stage micrometer units
if each stage micrometer unit = 0.1mm, the length of 80 eyepiece units = 0.1x20=2mm
one eyepiece unit = 2/80 = 0.025mm
0.025 mm = __ µm
25
the pressure in the circulatory system is generated by what?
contractions of the ventricles in the heart
- the pressure in the main arteries leaving the heart is at its highest
- blood entering the main artery on the left side (the aorta) has the highest pressure as the left ventricle muscle is thicker and generates most pressure
- as blood enters the aorta (and other smaller arteries), the vessel expands until it reaches a maximum and recoils, pushing the blood forwards
- where arteries pass close under the skin, this expansion and recoil is felt as a pulse
- the flow in the aorta, arteries and arterioles is described as pulsatile; the pressure goes up when the ventricles contract and drops when the ventricles relax
- pressure drops from the aorta to the arteries to the arterioles, this is because the total cross-sectional area of smaller vessels is larger than that of larger vessels
- narrower vessels have more resistance to the flow of blood
- capillaries are small and numerous and very narrow, so blood loses pressure rapidly
- without elastic fibres in the walls there can be no pulsatile flow, the flow becomes laminar
- blood drains into venules, veins and the vena cava ; as the vessels get wider, the pressure drops further
- the same pattern i seen in the pulmonary circulation, but the pressures are much lower as the right ventricle has a much thinner muscle than the left
what does it mean that the heart is a double pump?
it is divided in two by an internal septum making the right and left sides separate
- the two sides contract and relax simultaneously, but the right side pumps blood to the lungs and the left pumps blood to the body
the top two chambers of the heart are the ___?
atria
which are small
(the bulk of the heart is the ventricles)
what does the pulmonary artery do?
takes blood to the lungs
what do the (superior and inferior) vena cava do?
return blood to the heart from the head and body respectively
what does the pulmonary vein do?
return blood from the lungs
what does the coronary artery do?
supply the heart MUSCLE with oxygen and glucose
the aorta loops round, forming ____
an aortic arch
the heart is separated into right and left sides by the ___?
septum
- the ‘walls’ of each chamber are made of cardiac muscle, a specialised skeletal muscle that is resistant to tiring
structure of the heart + process:
- atria at the top of the heart, ventricles at the bottom
- between the ventricles and atria are valves to prevent backflow
- these valves are the atrioventricular valves, the right one is the tricuspid, left bicuspid
- blood enters the heart from the vena cave and pulmonary veins into the atria and then is pushed through the ventricles as the atria contact
- when the ventricles contract, the atria are relaxed
- the blood is pushed out through the aorta and pulmonary arteries at the top of the heart
- the atrioventricular valves are forced to shut to prevent backflow to the atria and the chordae tendineae (heart strings) prevent the valves turning inside out
- at the base of the two arteries are semi lunar valves, the aortic valve at the base of the aorta and the pulmonary valve at the base of the pulmonary artery
- when the ventricle relaxes, the semi-lunar valves fill with blood and close preventing backflow from the arteries to the ventricles
what valves are found between the ventricles and atria?
atrioventricular valves
- right = tricuspid (LEARN we always ‘tri’ to be right)
- left = bicuspid
what prevent the valves turning inside out when they shut?
chordae tendineae (heart strings)
what valves are found at the base of the two arteries?
semi-lunar valves
- aortic valve at the base of the aorta
- pulmonary valve at the base of the pulmonary artery
in what order does blood always flow through in the heart?
vein —> atrium —> ventricle —> artery
the left ventricle wall is (less/more) muscular than the right?
more
the aorta leaves the left (atrium/ventricle)?
ventricle
pressure changes in the heart:
- conventionally, the blood flow is described as starting with the atria contracting - atrial systole
- when the atria contract the pressure in the atria is higher than that in the ventricles and blood is pushed through the open atrioventricular valves into the ventricles. at this point, the ventricles are relaxed (in diastole)
- when the ventricles are full, they contract from the apex upwards. the pressure in the ventricles increases rapidly and quickly exceeds that of the atria, pushing the atrioventricular valves shut
- the pressure is raised above that of the arteries and the semi-lunar valves are forced open. blood is pushed upwards and into the arteries
- as the ventricles relax, the pressure falls below that in the arteries. the semi-lunar valves fill with blood and close, preventing blood flowing backwards into the ventricles. the pressure in the ventricles continue to drop until it is below that of the atria, blood flows from the veins through the atria and the ventricles start to fill. the heart is in diastole
- the atria contract … and the whole process starts again
blood flows from atria to ventricles and then to arteries because of pressure generated by contractions of the heart muscle
pressure in the arteries doesn’t drop to 0 because of ____?
the semi-lunar valves closing
contraction is called (systole/diastole)?
relaxation is called (systole/diastole)?
contraction = systole
relaxation = diastole
(DIastole = when you DIe you are very relaxed)
semi-lunar valves close when the pressure in the arteries is (higher/lower) than that in the ventricles?
higher
what does it mean that the heart is myogenic?
the heart is stimulated to beat from within its muscle wall (capable of contracting without nervous impulse)
- if the heart is isolated from its nerve supplies, it will continue to beat, but irregularly
- heart rate is regulated by nerve impulses from the medulla oblongata in the brain
- the heartbeat is initiated within the cardiac muscle itself and is not dependent upon external stimulation
what is the sinoatrial node (SAN)?
- pacemaker
- group of cells in the right atrium
- sends out a wave of excitation (depolarisation of muscle cells) across the muscle of the atria
- the muscle responds by contracting (atrial systole)
(when the cells depolarise, they contract; when they relax, they are repolarized)
how is the wave of excitation sent out by the SAN prevented from passing to the ventricles?
by fibrous tissue between the atria and ventricles
what happens to the wave of excitation after it is sent out by the SAN?
passes to the atrioventricular node (AVN), located in the septum at the atrioventricular junction
what does the AVN do with the wave of excitation sent out by the SAN?
delays it, allowing the atria to complete contraction (fully emptying blood) and the ventricles to fill, ensuring that the ventricles contract after the atria
- then the AVN lasses the wave of excitation to the bundle of His in the septum
what happens once the wave of excitation reaches the bundle of His?
- it is passed through the bundle of His to the apex of the heart
this is important as the ventricles will contract from the apex upwards so that the blood will be pushed up to the arteries
- from the bundle of His, the wave of excitation passed through Purkinje fibres in the muscles of the ventricles. the spread is upwards through the ventricle walls, so the contraction begins at the apex
what is ECG an abbreviation for?
electrocardiogram
what is an ECG?
- a graph showing the electrical activity in the heart during the cardiac cycle
what does the P wave on an ECG represent?
- SAN generates electrical signals
- causes depolarisation of the atria during atria systole
- electrical activity during atrial systole
what does the QRS complex on an ECG represent?
- the depolarisation of the ventricles during ventricular systole
- electrical activity during ventricular systole
what does the T wave on an ECG represent?
- the repolarisation of the ventricles during ventricular diastole
- causes ventricular diastole
what is on the x-axis of an ECG?
time
(so an ECG trace can be used to calculate heart rate)
what do you term an ECG where the trace shows no pattern at all, waves of excitation are passing over the ventricles randomly?
what does it indicate?
ventricular fibrillation
- indicates that the person is having a heart attack
what do you term an ECG where the trace shows QRS complexes, but the P waves before are showing that electrical activity is happening randomly across the atria?
atrial fibrillation
the QRS complexes are not evenly spaced, the heart is ‘missing a beat’
what do you term an ECG where the trace shows that there are three waves between the QRS complex (indicates that some P waves are not followed by QRS)
heart block
- the atria are contracting but the wave is not passing to the ventricles
- there are different degrees of heart block - the treatment is to install a pacemaker in the AVN which takes over the transmission to the bundle fibres
- heart block may also manifest as longer than usual P-Q intervals or almost flat lines between the QRS complexes, which are often wider than usual
what is a slow heart rate on an ECG termed?
bradycardia
(<50bpm)
what is a rapid heart rate on an ECG termed?
tachycardia
(>100bpm)
what is the shape of rbc?
adaptions?
biconcave disc
- as provides a large surface area to maximise diffusion of oxygen into cells
- disc shape minimised the diffusion pathway for oxygen
- the thinner central section allows the rbc the flexibility to squeeze through capillaries
- rbc have no nucleus or organelles - giving more space to maximise the no. of haemoglobin molecules
- lack of mitrochondria means thst oxygen is not used up in aerobic respiration while the oxygen is transported
why is a lack of mitochondria an advantage to rbc?
- means that oxygen isn’t used up in aerobic respiration while the oxygen is transported
what does haemoglobin consist of?
- quaternary structure protein consisting of 4 polypeptide chains, two alpha chains and two beta chains
- also a prosthetic group containing an iron ion (Fe2+)
each haemoglobin molecule can carry ___ oxygen molecules?
4 oxygen molecules
(eight atoms of oxygen)
when haemoglobin is attached to oxygen, what is it termed?
oxyhaemoglobin (HbO8)
can rbc replicate by mitosis?
no as they lack a nucleus
when blood enters the lung capillaries from the pulmonary arteries, it has (high/low) oxygen and (high/low) carbon dioxide?
low oxygen
high carbon dioxide
loading and unloading oxygen:
- oxygen diffuses into the rbc and binds to the haemoglobin inside (called loading or association)
- the blood returns to the heart via the pulmonary veins and is then pumped into the systemic circulation
- no gas exchange happens until the blood reaches the capillary of the body tissues
- at the body tissues the haemoglobin unloads oxygen to be used in respiration (dissociation)
the amount of loading and unloading of oxygen is dependent on what?
the partial pressure of oxygen surrounding the capillaries
- in the lungs the capillaries are in close contact with air high in oxygen in the alveoli and therefore load oxygen
- if a tissue has a high rate of aerobic respiration it will have a low partial pressure of oxygen and haemoglobin will unload more oxygen than it would to a tissue with a lower rate of respiration
- this relationship can be represented graphically as an ‘oxygen dissociation curve’
what does the oxygen dissociation curve show the relationship between?
the oxygen partial pressure and how much oxygen is carried by haemoglobin (% saturation of haemoglobin)
why is oxygen measured as a partial pressure?
bc about 21% of air is oxygen; but the pressure of air changes with altitude, so at the top of Mt.Everest there would still be 21% concentration of oxygen, but less air pressure would mean fewer molecules of oxygen in a given volume
theoretically, the relationship between the partial pressure of oxygen and % saturation is linear: the more oxygen there is the more can be carried.
in practice, what is the relationship between them? why?
- as haemoglobin binds co-operatively with oxygen, the curve is sigmoid (s-shaped)
- as each oxygen molecule binds to haemoglobin, it causes a conformational shape change in the protein meaning it is easier to bind the next oxygen molcule
what does the flat part of the oxygen dissociation curve mean?
full saturation of haemoglobin, even if the air pressure drops a small amount
how have organisms that live in low oxygen environments adapted?
they have haemobglobin that fully saturates at lower ppO2
- their haemoglobin has a higher affinity for oxygen than adult human haemoglobin. (oxygen dissociation curve is to the left of the standard human Hb curve)
- this means that their haemoglobin is fully saturated at lower ppO2
how does a foetus gain its oxygen?
- from its mother’s blood across the placenta
- foetal haemoglobin has a higher affinity for oxygen than adult haemoglobin, so a foetus can absorb oxygen from the mother’s blood at all ppO2.
- the curve is to the left of the adult curve
the oxygen dissociation curve for foetal haemoglobin is to the (right/left) of the adult curve?
left
what is a disadvantage of oxygen dissociation curves to the left?
- oxyhaemoglobin doesn’t dissociate as easily
- myoglobin is a different respiratory pigment found in muscle cells
- it can only bind to one molecule of oxygen
- it loads at much lower ppO2 and acts as an oxygen store, only releasing oxygen at very low partial pressures when the muscles are respiring quickly
- this delays the onset of anaerobic respiration
what does carbon dioxide dissolve in water to form (after it diffuses into the rbc)? what is the reaction catalysed by?
carbonic acid (H2CO3)
the reaction is catalysed by the enzyme carbonic anhydrase
what does carbonic acid dissociate into?
- protons (H+)
- hydrogen carbonate ions (HCO3 -)
what are the 3 ways that carbon dioxide is carried in the plasma?
- diffuse into the plasma as hydrogen carbonate ions HCO3 - (85%)
- diffuse into rbc and attach to haemoglobin forming carbaminohaemoglobin (10%)
- dissolved in plasma (5%)
what is the chloride shift?
- process by which chloride ions move into the erythrocytes in exchange for hydrogen carbonate ions which diffuse out of the erythrocytes
- 1 to 1 exchange
are the reactions of how CO2 is released from the blood into the alveoli reversible?
yes
- carbonic acid dissociates into protons (H+) and hydrogen carbonate ions (HCO3 -)
- the hydrogen carbonate ions diffuse into the plasma
- chloride ions diffuse into the rbc to maintain electrochemical neutrality in the cells
- the exchange is one to one; one hydrogen carbonate ion diffuses out of the cell and one chloride ion diffuses into the rbc
- this is called the chloride shift
- and balances the charge in plasma and the rbc
- the protons bind to haemoglobin displacing oxygen from the oxyhaemoglobin.
- the oxygen dissociates and diffuses into the cells
the diffusion of Cl- into red blood cells is called what?
the chloride shift
what effect do H+ have on HbO8?
cause oxygen to dissociate
what is the Bohr shift?
- when respiration rates are high, more CO2 is produced by cells
- more CO2 diffuses into the rbc
- more CO2 dissolves in the rbc and more carbonic acid is formed
- the more carbonic acid is formed, the more dissociation there is
- the more dissociation, the more H+ ions are released causing more oxyhaemoglobin to dissociate
- thus, more oxygen is released to the cells as the oxyhaemoglobin dissociates at higher ppO2 than usual
- the oxygen dissociation curve is shifted to the right, it shifts further to the right the higher the CO2 production
- the further the curve is shifted the more oxygen is released to be used in aerobic respiration
the same response can be seen if blood becomes acidic or if the temperature is raised
the further the shift to the right, the (higher/lower) the affinity of haemoglobin for oxygen and the (more/less) oxygen is released to cells?
lower
more
what are some examples of thing transported in the blood?
- oxygen
- carbon dioxide
- hormones
- glucose
- urea
- white blood cells
- proteins
- salt/ions
all affect water potential
what is tissue fluid?
- the fluid that surrounds all cells
- the area between blood vessels and cells which is filled with a watery fluid
- has all the components of plasma except plasma proteins or rbc
- allowing for transport between blood and cells
- contains dissolved oxygen and nutrients which serve as a means of supplying the tissues with the essential solutes in exchange for waste products such as co2. ∴ enables exchange of substances between blood and cells
what is tissue fluid needed for?
- capillaries transport blood through the tissues
- blood contains all the materials the cells need for metabolism
- the various substances have to pass from the plasma and rbc into the tissues and then into the cells
- they do this by diffusing through the fluid surrounding the cells called the tissue fluid
to summarise, what are the functions of tissue fluid?
- bathe all cells
- help maintain a constant environment around cells
- supply oxygen, glucose, hormones and ions to cells
- remove waste from cells
at the arterial end of the capillary bed, the hydrostatic pressure difference is ___ than the osmotic difference?
higher
at the venule end of the capillary bed, the hydrostatic pressure difference is ___ than the osmotic difference?
lower
at the aterial end, tissue fluid is ____?
formed
at the venule end, tissue fluid is ____ to the blood?
reabsorbed
as blood flows through capillaries, hydrostatic pressure gets ___?
lower
as blood flows through capillaries, the water potential gets ___?
lower
what is oedema?
swelling caused by more tissue fluid being formed than can be reabsorbed or drained by the lymph vessels
what is kwashiorkor caused by?
- caused by severe protein deficiency
- a lack of protein in the blood raises the water potential, meaning at the venule end of the capillary, the osmotic gradient is lower than normal
- less tissue fluid is drained into the lymph vessels, causing oedema
what can cause oedema (swelling caused by more tissue fluid being formed than can be reabsorbed or drained)?
- keashiorkor
- blockage of lymph vessels, by parasites or external pressure from tumours, means that less tissue fluid is drained into the lymph vessels, causing oedema
- high blood pressure csn cause oedema by increasing the hydrostatic pressure, forcing more fluid out of the capillaries
briefly describe the vascular system of insects?
- open circulatory system
- dorsal-tube shaped heart
- respiratory gases not carried in blood
briefly describe the vascular system of earthworms
- vascularisation (process of growing blood vessels)
- closed circulatory system
- respiratory gases carried in blood
what are some advantages of a closed circulatory system?
- blood pressure can be maintained
- blood supply to different organs can vary / be controlled by constricting or dilating blood vessels
- lower volumes of transport fluid required
- blood can move relatively rapidly
describe the double circulatory system in humans:
blood flows through the heart twice in a complete circuit:
- pulmonary circuit
- systemic circuit
describe the pathway of blood around the body, naming the structures of the heart:
- pulmonary vein
- left atrium
- left ventricle
- aorta
- body
- vena cava
- right atrium
- right ventricle
- pulmonary artery
- lungs
what is the function of arteries?
carry blood away from the heart to the tissues, at high pressure
relate the structure of arteries to their function:
- thick, muscular walls to handle high pressure without tearing
- elastic tissue allows recoil to prevent pressure surges
- narrow lumen to maintain pressure
what is the function of veins?
carry blood towards the heart under low pressure
relate the structure of veins to their function:
- thin walls due to lower pressure
- require valves to ensure blood doesnt flow backwards
- have less muscular and elastic tissue as they dont have to control blood flow
what is the function of capillaries?
form a large network through the tissues of the body and connect arterioles to the venules
relate the structure of capillaries to their function:
- walls only one cell thick so short diffusion pathway
- very narrow so can permeate tissues and rbc can lie flat against the wall, reducing the diffusion distance
- numerous and highly branching, providing a large surface area
what is the function of arterioles?
connect the arteries and the capillaries
what is the function of the venules?
connect the capillaries and the veins
relate the structure of arterioles and venules to their function:
- branch off arteries and veins in order to feed blood into capillaries
- smaller than arteries and veins so that the change in pressure is more gradual as blood flows to the capillaries
what is the cardiac cycle?
- the sequence of events involved in one complete contraction and relaxation of the heart
- three stages : atrial systole, ventricular systole and diastole
describe what happens during ventricular diastole?
- the heart is relaxed
- blood enters the atria, increasing the pressure and pushing open the AV valves
- this allows blood to flow into the ventricles
- pressure in the heart is lower than in the arteries, so SL valves remain closed
describe what happens during atrial systole?
- the atria contract, pushing any remaining blood into the ventricles
- AV valves pushed fully open
describe what happens during ventricular systole?
- the ventricles contract
- the pressure in the ventricles increases, closing the AV valves to prevent backflow and opening the SL valves
- blood flows into the arteries
why is cardiac muscle described as myogenic?
- it initiates its own contraction without outside stimulation from nervous impulses
(but it can be regulated, by the sinoatrial node which initiates a wave of excitation across both atria)
explain how the heart contracts:
- SAN initiates and spreads impulse across the atria, so they contract
- AVN receives, delays and then conveys the impulse down the bundle of His
- impulse travels into the Purkyne fibres which branch across the ventricles, so they contract from the bottom up
describe the structure and function of erythrocytes:
- type of blood cell that is anucleated and biconcave
- contains haemoglobin which enables the transport of oxygen and carbon dioxide to and from the tissues
red blood cell
what is plasma?
- main component of the blood (yellow liquid) that carries red blood cells
- contains proteins, nutrients, mineral ions, hormones, dissolved gases and waste. also distributes heat
describe the role of haemoglobin:
- present in rbc
- oxygen molecules bind to the haem groups and are carried around the body, then released where they are needed in respiring tissues
how does partial pressure of oxygen affect oxygen-haemoglobin binding?
haemoglobin has variable affinity for oxygen depending on the partial pressure of oxygen
- at high ppO2, oxygen associates to form oxyhaemoglobin
- at low ppO2, oxygen dissociated to form deoxyhaemoglobin
write an equation for the formation of oxyhaemoglobin:
Hb + 4O2 ⇌ Hb•4O2
note that full saturation is rare
explain the shape of oxyhaemoglobin dissociation curves:
sigmoidal curve (s shaped)
- when first O2 molecule binds, it changes the tertiary structure of haemoglobin so that it is easier for the second and third molecules to bind
- third molecule changes the tertiary structure of haemoglobin so that it is more difficult for the fourth molecule to bind
how does foetal haemoglobin differ from adult haemoglobin?
- has a higher affinity for oxygen than adult haemoglobin due to the presence of two different subunits that allow oxygen to bind more readily
why is the higher affinity of foetal haemoglobin important?
enables the foetus to obtain oxygen from the mother’s blood
predict the shape of the dissociation curves of animals adapted to low oxygen level habitats:
- haemoglobin has a greater affinity for oxygen
- haemoglobin is saturated at a lower ppO2
- therefore dissociation curve to the left
why is the chloride shift important?
it maintains the electrochemical equilibrium of the cell
what is the function of carbonic anhydrase?
catalyses the reversible reaction between water and carbon dioxide to produce carbonic acid
write equations to show the formation of hydrogen carbonate ions in the plasma:
carbonic anhydrase enzyme catalyses:
CO2 + H2O ⇌ H2CO3 (carbonic acid)
carbonic acid dissociates:
H2CO3 ⇌ HCO3 - (hydrogen carbonate ions) + H+
state the Bohr effect?
the loss of affinity of haemoglobin for oxygen as the partial pressure of carbon dioxide increases
explain the role of carbonic anhydrase in the Bohr effect:
- carbonic anhydrase is present in rbc
- catalyses the reaction of CO2 and water to form carbonic acid, which readily dissociates to produce H+ ions
- H+ ions combine with the haemoglobin to form haemoglobinic acid
- encourages oxygen to dissociate from haemoglobin
hydrostatic pressure is higher at what end of the capillary?
higher at aterial end of capillary than venous end
what is oncotic pressure in the formation of tissue fluid?
changing water potential of the capillaries as water moves out, induced by proteins in the plasma
how is tissue fluid formed?
- as blood is pumped through increasingly smaller vessels, hydrostatic pressure is greater than oncotic pressure
- so fluid moves out of the capillaries
- it then exchanges substances with the cells
why does blood pressure fall along the capillaries?
- friction
- lower volume of blood
what happens at the venous end of the capillary?
- oncotic pressure is greater than hydrostatic pressure
- fluid moves down its water potential gradient back into the capillaries
where does some tissue fluid drain?
- some drains into the lymphatic system and eventually returns to the blood
haemocoel definition
- the main body cavity found in most invertebrates that contains a circulatory fluid
do earthworms have a single or double circulatory system?
single circulatory system
what is the important structure of an arteriole?
the smooth muscle tissue, which can widen or narrow the lumen to increase or decrease blood flow
- they have a large total surface area and relatively narrow lumen causing a further reduction in pressure and rate of blood flow
what is the width of an artery?
0.1 - 10mm
what is the width of a capillary?
8 - 10 µm
what is the width of a vein?
0.1 - 20 mm
blood flow through the heart:
- blood enters the heart from the head and body via the vena cava into the right atrium
- the right atrium contracts (atrial systole) forcing blood through the right atrio-ventricular valve into the right ventricle, which is relaxed
- the right ventricle contracts (ventricular systole) forcing blood out of the heart through the semi-lunar valve to the lungs via the pulmonary artery
- oxygenated blood returns from the lungs to the heart via the pulmonary vein and enters the left atrium when the left atrium is relaxed (total diastole)
- the left atrium contracts, forcing blood through the left semi-lunar valve into the aorta and then to the rest of the body
- this describes one circuit that blood takes. during the cardiac cycle, both atria contract simultaneously followed by the contraction of both ventricles
- valves ensure that blood flows in a unidirectional manner i.e prevent backflow
what is the cardiac output?
the stroke volume x heart rate
in other words, the total volume of blood pumped by the heart per minute is the volume of blood pumped per beat multiplied by the number of times the heart beats in a minute
cardiac cycle:
- left atrium contracts so volume of atrium decreases and pressure increases
- when blood pressure in left atrium exceeds that in left ventricle, blood flows into the left ventricle
- the ventricle then contracts (ventricular systole) and pressure rises in left ventricle as volume decreases
- as the ventricle contracts blood is pushed against the atrioventricular valves closing them and preventing blood flow back to the atria
- when pressure in left ventricle exceeds that in the aorta, the semi-lunar valves open and blood flows out into the aorta
- left ventricle then relaxes (diastole) so its volume increases and pressure falls
- when pressure in ventricle drops below that of the aorta, blood tried to flow back into the ventricle from the aorta, pushing against the left semi-lunar valve closing it
- when pressure in left ventricle drops below that in the left atrium, the left atrio-ventricular valve opens and the cycle begins again
- remember : blood always flows from a region of high pressure to low pressure unless a valve prevents it
what are the Purkinje fibres?
network of fibres in the wall of the ventricles
how can you calculate heart rate using an ECG?
by measuring the time taken from one point on the ECG trace to the next
60/time found = __ bpm
what is the atrial systole?
- wave of excitation spreads out from the SAN across both atria
- both atria start contracting
- wave cannot spread to ventricles due to layer of connective tissue
- wave spreads via the AVN, through the bundle of His to apex of ventricle
what is the ventricular systole?
- the bundle of His branches into Purkinje fibres carrying wave upwards through ventricle muscle causing it to contract
- ventricle contraction is therefore delayed and contraction is from base upwards
why is the Bohr effect useful?
it supplies oxygen more quickly to respiring tissues, where it is needed
insects circulatory system:
- open circulatory system
- insect blood (hemolymph) flows freely throughout the body cavity + direct contact with organs and tissues
- insect circulatory system doesnt carry oxygen so the blood doesnt contain rbc. haemolymph is usually green or yellow
- a single blood vessel runs along the dorsal side of the insect
- few little pumps (hearts) push the haemolymph through this vessel (in one direction) to the haemocoel
- the haemolymph is then reabsorbed by the dorsal vessel
earthworms circulatory system:
- closed circulatory system
- the blood contains an oxygen-carrying pigment
- major blood vessels:
- dorsal blood vessel - distributed blood to various parts of the body
- branches of the dorsal blood vessel - take the blood to all the structures within each segment
- ventral blood vessel - collects blood from the body
- there are 5 pseudo-hearts to pump the blood around
fish circulatory system:
- single circulation
- blood pressure reduced as blood passes through the gill capillaries
- slows down flown to the rest of the body
- limits the rate of delivery of O2 and nutrients to cells and removal of waste
- efficient for the level of activity of fish - also fish dont maintain their body temp so need to respire relatively less than mammals
mammals circulatory system:
- double circulation
- more efficient
- heart comprised of 2 separate pumps
- necessary bc of higher activity level and need to maintain their body temp at 37.C through respiration
- need to deliver and remove materials to and from cells rapidly - achieved by delivering blood at high pressure to tissue
how are contractions of the heart coordinated?
through the:
- sinoatrial node (SAN) aka the pacemaker
- atrioventricular node (AVN)
- purkyne (purkinje) tissue
in order for the heart to function efficiently, contractions of the heart must be coordinated
what does the Q-T interval mean on an ECG?
contraction time (ventricles contracting)
what does the T-P interval mean on an ECG?
filling time (ventricles relaxed and filling with blood)
in respiring tissue, oxygen ___ from haemoglobin?
dissociates (releases)
what is partial pressure measured in?
kPa
what allows lung tissue to have a high pO2?
ventation
description of each oxygen molecule associating to the haemoglobin:
- after the first oxygen molecule associates, the conformation of the haemoglobin changes
- conformational change makes it easier for the 2nd and 3rd oxygen molecule to associate
- it is difficult to associate a 4th oxygen molecule
- this is bc the haemoglobin molecule becomes ‘full’
- this is why the curve plateaus below 100%
tissue fluid is the result of an interplay of:
- hydrostatic pressure
- osmosis
what is hydrostatic pressure?
- the pressure of the blood from heart contractions - it forces fluid out of the capillaries
- fluid moves out through tiny gaps in the capillary walls
- dissolved gases and nutrients move with it
- larger plasma proteins and cells DO NOT
- some hydrostatic pressure from the tissue fluid forces fluids back into the capillaries - but the net movement is out
- creates when blood is pumped along the arteries, into arterioles and then capillaries
- this pressure forces blood fluid out of the capillaries
what is osmosis (in terms of forming tissue fluid)?
- a net loss of water from the capillaries (due to hydrostatic forces) gives them a more negative water potential
- water moves down the water potential gradient into the capillaries
lymph:
- note that not all fluid passes back into the capillaries
- this excess output needs to be collected to avoid tissue swelling
- this net excess is drained into the vessels of the lymphatic system - this fluid is known as lymph
do arteries carry oxygenated or deoxygenated blood?
oxygenated
do capillaries carry oxygenated or deoxygenated blood?
both
do veins carry oxygenated or deoxygenated blood?
deoxygenated
explain why larger organisms need to have transport systems? [3]
- s.a relative to vol too small
- diffusion too slow
- distance too great
- insufficient
- have a higher activity level so need more energy so need more oxygen
the heart is made of this kind of muscle:
cardiac
heart muscle can initiate its own contraction so it is referred to as this:
myogenic
which group of muscles, the atria or ventricles tend to beat at a higher frequency?
atrial
if the contractions of the heart is not synchronised, the heart will be in?
fibrillation
the small patch of tissue in the right atrium that generates electrical activity:
sinoatrial node (SAN)
this patch of tissue sets the rhythm of the heart so it is sometimes referred to as the pacemaker
when the atria contract, it is referred to as:
atrial systole
the only route through down to the ventricles is via the:
AVN
the muscle tissue that separates the two ventricles:
(interventricular) septum
the tissue that takes the excitation wave to the apex of the heart:
purkyne
what are the 3 types of fluid associated with the circulatory system?
- blood
- tissue fluid
- lymph
what is the blood pressure like at the arteries? veins? capillaries?
arteries = high pressure
veins = low pressure
capillaries = pressure changes
capillary walls are ____ ____, allowing some things to pass from the blood to the tissue?
partially permeable
what is the main source of hydrostatic pressure?
contractions of the heart
what are some examples of the things that move with the fluid from hydrostatic pressure?
- glucose
- oxygen
- carbon dioxide
- water
what are some examples of the things that doesn’t move with the fluid from hydrostatic pressure?
- proteins
- red blood cells
suggest the effect that a first degree heart block would have on the functioning of the heart? (due to it increasing distance between P wave and QRS meaning AVN affected)
slower heart rate
what is the name given to the difference between the two curves caused by a change in pH?
Bohr effect
what could account for the lowering of tissue fluid pH in the muscles?
release of CO2 during aerobic respiration - forming carbonic acid
this would be an advantage during exercising as MORE oxygen is released
explain why fluid will accumulate in the tissues of a person whose diet is poor in protein? [3]
- decrease plasma protein
- increase water potential of blood
- decrease potential gradient
- decrease water reabsorbed
explain the significance of the effect of an increase in pCO2 for respiring muscle tissue [2]
- reduced affinity of haemoglobin for oxygen / (oxy)haemoglobin dissociates at a higher partial pressure (of oxygen)
- MORE oxygen (released/unloaded/dissociated) / oxygen released (more) readily
allow oxygen more readily dissociated from haemoglobin = 2 marks
respiratory minute volume is the volume of gas inhaled or exhaled from a person’s lungs per minute. the minute volume of a healthy person during normal breathing at rest is 6-7dm^3min^-1. in people with chronic diseases, such as heart disease, the minute volume is 12-16 dm^3min^-1.
explain how an increase in minute volume results in a decrease in pCO2 of blood in alveolar capillaries [2]
- CO2 removed faster/more CO2 exhaled
- increases (diffusion/concentration) gradient (from blood into alveoli)
most carbon dioxide is carried as hydrogen carbonate ions (HCO3 -) in the plasma. the following chemical pathway shows how carbon dioxide is converted into HCO3 - in a red blood cell.
CO2 + H2O -X-> Y —> Z + HCO3 -
identify X, Y and Z
X = carbonic anhydrase
Y = carbonic acid / H2CO3
Z = hydrogen ION / H+ / proton
