3.4.1 Mass transport in animals Flashcards
What is the structure of the cardiac muscle?
The walls of the heart have a thick, muscular layer. The cardiac muscle is only found in the heart.
What are the unique properties of the cardiac muscle?
Myogenic and never fatigues (as long as there is an O2 supply).
What does myogenic mean?
It can contract and relax without receiving signals from nerves (stimulation).
What do the coronary arteries do?
Supply the cardiac muscle with oxygenated blood and glucose (for aerobic respiration).
Where do the coronary arteries branch off from?
The aorta.
What happens if the coronary arteries become blocked?
The cardiac muscle cannot receive O2 and glucose, therefore cannot aerobically respire, and therefore dies, resulting in a heart attack.
What is another name for a heart attack?
Myocardial infarction.
What blood vessel brings oxygenated blood from the lungs to the left atrium?
Pulmonary vein.
What blood vessel brings oxygenated blood from the left ventricle to the rest of the body?
Aorta.
What blood vessel brings deoxygenated blood from the body to the right atrium?
Vena cava.
What blood vessel brings deoxygenated blood from the right ventricle to the lungs?
Pulmonary artery.
What valve separates the left atrium and left ventricle?
Bicuspid valve.
What valve separates the left ventricle and the aorta?
Aortic valve.
What valve separates the right atrium and the right ventricle?
Tricuspid valve.
What valve separates the right ventricle and the pulmonary artery?
Semilunar valve.
What are the 4 chambers of the heart?
Right atrium, left atrium, right ventricle, left ventricle.
What is the structure of the atria?
Thinner muscular walls (than ventricles) and elastic walls - stretch when blood enters.
Why do the atria have thinner muscular walls than the ventricles?
Do not need to contract as hard; only pushing blood into ventricles (short distance + down with gravity).
What is the structure of the ventricles?
Thicker muscular walls (than atria).
Why do the ventricles have thicker muscular walls than the atria?
Enable bigger contraction (with greater force) to push blood out at a higher pressure, as it is travelling a further distance and against gravity.
Why is it good for the blood leaving the ventricles to be at a higher pressure?
The higher blood pressure enables blood to flow longer distances.
What is the structure of the right ventricle?
Pumps blood to the lungs and has a thinner muscular wall (than the left ventricle).
Does the right ventricle have a thinner muscular wall than the left ventricle?
Yes.
Why does the right ventricle have a thinner muscular wall than the left ventricle?
Right ventricle needs blood at a lower pressure (as only going to lungs), whereas blood from left ventricle can be at a higher pressure (as going to rest of body).
Why does the right ventricle need blood at a lower pressure?
To prevent damage to capillaries in the lungs and so blood flows slowly to allow more time for gas exchange.
Why is it important for blood to flow slowly near the lungs?
Allows more time for O2 to diffuse in and CO2 to diffuse out.
What is the structure of the left ventricle?
Thicker muscular wall (compared to right ventricle) and pumps blood to the body.
Why does the left ventricle have a thicker muscular wall than the right ventricle?
To enable bigger contractions of the muscle to create a higher pressure; needs to contract with the highest force to pump blood out at the highest pressure.
Why does the left ventricle need to pump blood out at the highest pressure?
To ensure it reaches all respiring cells in the body.
What 2 veins carry blood INTO the lungs?
Vena cava and pulmonary vein.
What does the vena cava do?
Carries deoxygenated blood from the body to the right atrium.
What does the pulmonary vein do?
Carries oxygenated blood from the lungs to the left atrium.
What does pulmonary refer to?
The lungs.
What 2 arteries carry blood AWAY from the heart?
Pulmonary artery and aorta.
What does the pulmonary artery do?
Carries deoxygenated blood from the right ventricle to the lungs.
What does the aorta do?
Carries oxygenated blood from the left ventricle to the rest of the body.
How many flaps does the bicuspid valve have?
2.
How many flaps does the tricuspid valve have?
3.
When do valves open?
When pressure is higher BEHIND the valve.
When do valves close?
When pressure is higher IN FRONT of the valve.
What is the role of valves?
Prevent back flow of blood.
What does the septum do?
Separates the oxygenated + deoxygenated blood and maintains a high concentration of oxygen in oxygenated blood to maintain a concentration gradient to enable diffusion at respiring cells.
What are the 3 stages of the cardiac cycle?
Diastole, atrial systole, ventricular systole.
What happens to the atria and ventricular muscles during diastole?
They are relaxed.
What happens to blood during diastole?
Enters the atria via the vena cava + pulmonary vein.
What happens to the pressure in the atria during diastole?
Increases - due to the blood flowing into the atria.
What happens to the atria muscles during atrial systole?
They contract.
What is the effect in the atria from the atria and ventricular muscles contracting?
The pressure increases further, causing the atrioventricular valves to open and blood to flow into the muscle.
What happens to the ventricular muscles during atrial systole?
They relax - ventricular diastole.
What happens between atrial systole and ventricular systole?
A short delay.
What happens to the ventricular muscles during ventricular systole?
They contract, increasing the pressure beyond that of the atria.
What is the result of the pressure in the ventricles increasing beyond that of the atria?
The atrioventricular valves close and the semilunar valves open.
What happens to the blood during ventricular systole?
It is pushed out into the arteries.
When do the atrioventricular valves open?
When the pressure in the atria is greater than the pressure in the ventricles.
When do the atrioventricular valves close?
When the pressure in the ventricles is greater than the pressure in the atria.
When do the semilunar valves open?
When the pressure in the ventricles is higher than the pressure in the arteries.
When do the semilunar valves close?
When the pressure in the arteries is greater than the pressure in the ventricles.
What happens to the volume of the atria during atrial systole?
Decreases.
What happens to the volume of the atria during ventricular systole?
No change.
What happens to the volume of the atria during diastole?
Increases.
What happens to the pressure in the atria during atrial systole?
Increases.
What happens to the pressure in the atria during ventricular systole?
No change.
What happens to the pressure in the atria during diastole?
Increases.
What happens to the volume of ventricles during atrial systole?
Increases.
What happens to the volume of ventricles during ventricular systole?
Decreases.
What happens to the volume of ventricles during diastole?
Slow increase.
What happens to the pressure in the ventricles during atrial systole?
Decreases.
What happens to the pressure in the ventricles during ventricular systole?
Increases.
What happens to the pressure in the ventricles during diastole?
Slow increase.
Atrial systole - description:
Atria contracts forcing blood into the ventricles.
Ventricular systole - description:
Ventricle contracts forcing blood into the arteries.
Diastole - description:
Both chambers relax.
Describe the mammalian circulatory system:
Closed and double circulatory.
What does it mean that the mammalian circulatory system is closed?
The blood remains within the blood vessels.
What does it mean that the mammalian circulatory system is double circulatory?
The blood passes through the heart twice.
In a mammalian circulatory system, what are the 2 circuits for?
One circuit which delivers blood to the lungs and the other delivers blood to the rest of the body.
Why do mammals need a double circulatory system?
To manage the pressure of blood flow.
Why does blood flow through the lungs at a lower pressure in the mammalian circulatory system?
Prevents damage to the capillaries in the alveoli and reduces the speed at which the blood flows, enabling more time for gas exchange.
Why does the oxygenated blood from the lungs go back to the heart to be pumped out at a higher pressure in a mammalian circulatory system?
Ensures the blood reaches all the respiring cells in the body.
What blood vessel transports blood from the heart to the body?
Aorta.
What blood vessel transports blood from the aorta to the liver?
Hepatic artery.
What blood vessel transports blood from the aorta to the gut?
Mesenteric artery.
What blood vessel transports blood from the aorta to the kidneys?
The renal artery.
What blood vessel transports blood from the kidneys to the vena cava?
Renal vein.
What blood vessel transports blood from the gut to the liver?
Hepatic portal vein.
What blood vessel transports blood from the liver to the vena cava?
Hepatic vein.
What blood vessel transports blood from the body to the heart?
Vena cava.
What is the role of arteries?
Carry blood away from the heart + into arterioles.
What is the role of arterioles?
Connect arteries to capillaries.
What is the role of the capillaries?
Pass through tissue (to allow diffusion).
What is the role of veins?
Carry blood back to the heart.
What is the muscle layer of arteries?
Thicker than veins so that constriction + dilation can occur to control volume of blood.
What is the elastic layer of arteries?
Thicker than veins to help maintain blood pressure; the walls can stretch and recoil in response to heart beat.
What is the wall thickness of arteries?
Thicker walls than veins to help prevent the vessels bursting due to the high pressure.
Do arteries have valves?
Yes.
What is the lumen of arteries?
Smaller lumen than veins.
What is the muscle layer of veins?
Relatively thin so cannot control blood flow.
What is the elastic layer of veins?
Relatively thin as the pressure is much lower.
What is the wall thickness of veins?
Thin as the pressure is much lower, so there is a low risk of bursting; the thinness means the vessels are easily flattened, which helps the flow of blood up to the heart.
Do veins have valves?
Yes.
What is the shape and size of the lumen in veins?
Irregular shape and much larger lumen than arteries.
What are the key features of capillary structure?
Form capillary beds at exchange surfaces, one cell thick, narrow diameter, no muscle layer, no elastic layer.
How does the narrow diameter of capillaries affect blood flow?
It slows blood flow down, allowing more time for diffusion.
What happens to red blood cells in capillaries?
RBCs can only just fit through and are squashed against the walls, maximizing diffusion.
What is the thickness of the muscle layer in arterioles compared to arteries?
Relatively thicker to help restrict blood flow into capillaries.
How does the elastic layer of arterioles compare to that of arteries?
Thinner than in arteries as the pressure is lower.
What is the wall thickness of arterioles compared to arteries?
Thinner as pressure is slightly lower.
What is the pathway a red blood cell takes from the kidney to the lungs?
Renal vein to vena cava to right atrium, then right ventricle to pulmonary artery.
What is one precaution to take when clearing away after dissection?
Carry/wash sharp instruments by pointing away from body.
What is another precaution to take when clearing away after dissection?
Disinfect instruments/surfaces.
How can an arteriole reduce blood flow into capillaries?
Muscle contracts, constricting/narrowing the lumen of the arteriole.
What can be concluded about the ventricles and arteries from the valve image?
Ventricle muscles relaxed, no blood movement into arteries.
What can be concluded about the atria and ventricles from the valve image?
Atria contracted, blood movement from atria into ventricles.
How does valve A maintain unidirectional flow of blood?
Pressure in left atrium is higher than in ventricle causing valve to open; pressure in left ventricle is higher than in atrium causing valve to close.
Why were aortic valves stored in an isotonic solution?
Same water potential as valve, prevents loss/gain of water by osmosis, prevents damage to cells/tissues.
Why were aortic valves stored in a solution containing an antibiotic?
Kills/stops growth of bacteria that could cause infection or disease.
Why did valve replacement surgery increase minimum blood pressure in the artery?
After surgery, valve works, preventing blood flow back into the heart.
How could cardiac output stay the same with a decreased resting heart rate?
Cardiac output = stroke volume x heart rate, so stroke volume increases.
What is the equation linking stroke volume, cardiac output, and heart rate?
Cardiac output = stroke volume x heart rate.
What is tissue fluid?
The fluid that surrounds cells in tissues.
What is tissue fluid made of?
Small molecules that leave the blood plasma, e.g. Oxygen, water, glucose, amino acids, fatty acids, and ions.
What is exchanged between cells and fluid - INTO cells?
Glucose + oxygen –> substances needed for aerobic respiration.
What is exchanged between cells and fluid - OUT OF cells?
CO2 and Urea —> waste products of metabolic processes.
What is hydrostatic pressure?
The pressure created by fluid pushing against the walls of the container that it is in.
What causes high hydrostatic pressure?
The contraction of the left ventricle to pump blood out of the heart creates a high pressure.
What is ultrafiltration?
The process by which water and other molecules are forced out through tiny gaps in the capillary wall.
What does tissue fluid do?
Bathes the cells in the body that are outside of the circulatory system.
What substances are forced out of the capillary in ultrafiltration?
Water, oxygen, amino acids, fatty acids, glucose, ions, dissolved minerals.
Does pressure increase or decrease moving from arteriole to capillary?
Increase.
Why does pressure increase moving from arteriole to capillary?
The lumen size decreases.
Is there a high hydrostatic pressure in the arteriole end of the capillary?
YES.
What does the high hydrostatic pressure at the arteriole end of the capillary cause?
Smaller molecules and water to be forced out through tiny gaps in the capillary.
What molecules remain in the capillary during ultrafiltration?
Red blood cells, white blood cells, and plasma proteins.
Why must tissue fluid be reabsorbed?
Otherwise liquid will be constantly forced out, which leads to too much liquid around the cells, which would cause them to swell.
What end of the capillary is tissue fluid reabsorbed?
Venule end.
What end of the capillary is tissue fluid formed?
Arteriole end.
Is the hydrostatic pressure higher or lower at the venule end?
Lower.
Is there a higher or lower water potential in the capillary at the venule end?
Lower.
What does the lower water potential in the capillary cause?
Fluid to move INTO the capillary via osmosis.
Is an equilibrium eventually reached at the venule end?
Yes - once the water potentials have evened out.
What is reabsorbed at the venule end of the capillary?
Water, CO2, urea.
Is all tissue fluid reabsorbed at the venule end, and why?
NO - no more tissue fluid is reabsorbed once an equilibrium has been reached.
What happens to the remaining tissue fluid (once an equilibrium has been reached)?
The fluid forms lymph, and drains into the lymphatic system.
Why does the movement of water stop once an equilibrium has been reached?
No more osmosis can occur.
Do lymph vessels have valves?
Yes.
How does the left ventricle cause the blood to be at a high pressure?
The contraction of the thick muscular wall forces blood into the aorta.
What causes the decrease in blood pressure along the length of the capillary?
Friction reduces due to the reduction in fluid.
What is oncotic pressure?
The pressure created by the osmotic effects of the solutes in a solution.
If water moves out of an area, what happens to the oncotic pressure?
It decreases + becomes more negative.
Why is an arteriole described as an organ?
It is composed of different tissues.
How do muscle fibres in an arteriole reduce blood flow to capillaries?
As the muscle contracts, the arteriole narrows, reducing the size of the lumen.
Why does a capillary’s thin wall lead to rapid exchange of substances?
It provides a short diffusion pathway.
What is an advantage of slow blood flow in capillaries?
More time for exchange of substances.
What causes the decrease in blood pressure along the length of the capillary?
Loss of fluid.
How is fluid returned to the blood at the venous end of the capillary?
Low hydrostatic pressure at venule end and a higher concentration of blood proteins lead to water being returned by osmosis.
How does blockage of lymph vessels in the legs lead to swelling of tissues?
Swelling caused by fluid build up; fluid cannot be drained into the lymphatic system.
How do valves in larger lymph vessels assist the return of lymph to the blood plasma?
They stop the backflow of lymph and the pressure of surrounding tissues forces lymph along.
How is water exchanged between the blood and tissue fluid as blood flows along the capillary?
Hydrostatic pressure forces water out; hydrostatic pressure is greater than water potential; proteins remain increasing water potential; water returns via osmosis.
How does high blood pressure lead to an accumulation of tissue fluid?
High blood pressure = high hydrostatic pressure increases outward pressure from arterial end of capillary, so more tissue fluid is formed.
Why does hydrostatic pressure fall from the arteriole end to the venule end of the capillary?
Loss of fluid.
Why is the water potential of the blood plasma more negative at the venule end?
Water has left the capillary and proteins in blood are too large to leave, resulting in a higher concentration of blood proteins.
What is the role of the heart in the formation of tissue fluid?
Contraction of the left ventricle produces a high blood/hydrostatic pressure, forcing water and some dissolved substances out of the blood capillaries.
How does the structure of a capillary adapt it for the exchange of substances?
Fenestrations allow large molecules through; narrow lumen reduces flow rate; small diameter gives a large surface area to volume ratio; flattened endothelial cells reduce diffusion distances.
How is tissue fluid formed and returned to the circulatory system?
Hydrostatic pressure of blood is high at the arterial end; water and soluble molecules are forced out; proteins/large molecules remain; lowering the water potential; water moves back into the venous end of the capillary by osmosis; lymph system collects any excess tissue fluid.
Briefly describe the cardiac cycle.
Diastole - atria and ventricles are relaxed, semi-lunar valves are shut, blood enters the atria (from vena cava and pulmonary atery), pressure in atria opens atrioventricular valves, blood passes into ventricles, aided by gravity.
Atrial systole - both atria contract and remaining blood passes down to ventricles, ventricles remain relaxed
Ventricular systole - atria relax, both ventricles contract, pressure of blood forces the atrioventricular valves to shut, this increases pressure in ventricles, pressure increase opens the semi-lunar valves, so blood passes into the aorta and pulmonary artery.
How many polypeptide chains is haemoglobin made up of?
4
What types of polypeptide chains is haemoglobin made up of?
2 alpha and 2 beta chains
Is haemoglobin a globular or fibrous protein?
globular
What level of protein structure does haemoglobin have?
quaternary
Within the 4 polypeptide chains, how many haem groups are there?
4
What is a haem group?
a prosthetic group, containing iron
What are the 4 globin subunits held together by in haemoglobin?
disulphide bonds
Is haemoglobin soluble in water?
Yes
Why is haemoglobin soluble in water?
- the hydrophobic R groups face inwards
- the hydrophilic R groups face outwards
What is the word equation to form oxyhaemoglobin?
haemoglobin + oxygen —> oxyhaemoglobin
Can haemoglobin be in a tense or relaxed state?
both
When haemoglobin is in a relaxed state, it has a ___________ affinity for oxygen.
HIGH
What is positive cooperativity?
As soon as one oxygen molecule binds to a haem group, the remaining haem groups become exposed, making it easier for other oxygens to bind
When haemoglobin is in a tense state, it has a ________ affinity for oxygen.
LOW
What is loading?
the process by which haemoglobin binds with oxygen
What is loading also known as?
associating
What is unloading?
The process by which haemoglobin releases oxygen
What is unloading also known as?
dissociating
What is the X axis of the oxygen dissociation curve?
Partial pressure of oxygen/ kPa
What is the Y axis of the oxygen dissociation curve?
Saturation of haemoglobin with oxygen (%)
What are the 3 stages of the oxygen dissociation curve?
- Initial shallow gradient
- Steep gradient
- Flattening of gradient
Explain the ‘Initial shallow gradient’ part of the oxygen dissociation curve:
- initially the haemoglobin is in a tense state
- meaning it has a LOW affinity for oxygen
Explain the ‘steep gradient’ part of the oxygen dissociation curve:
- positive cooperativity occurs
- the haemoglobin moves into a relaxed state as more oxygen binds
- exposing the haem groups
Explain the ‘flattening of gradient’ part of the oxygen dissociation curve:
- less chance of collisions (between Hb and O2) occurring
- as the majority of binding sites (haem groups) are full
- so it is less likely that the 4th oxygen will bind with the 4th empty site.
What is the partial pressure of gas?
The amount of gas that is measured in a mixtures of gases, measured by the pressure it contributes to the total pressure of the gas mixtures.
Explain the Bohr effect:
- as the amount of CO2 increases, there is a fall in pH
- which reduces the affinity of haemoglobin for oxygen
- the haemoglobin changes shape and cannot hold onto the oxygen as easily
- the Hb moves into a more tense state
- means that more oxygen unloads in the tissue (for aerobic respiration)
(a) Haemoglobin is a protein with a quaternary structure. Explain the meaning of quaternary structure (1)
A molecule that contains more than one polypeptide chain
Give the formula for calculating the percentage saturation of haemoglobin with oxygen. (1)
(oxygenated haemoglobin/ maximum saturation) x 100
Suggest one advantage of the change in the affinity of haemoglobin for oxygen.
allows for the release of oxygen in the tissues
What term is used to describe the structure of a protein made of two or more polypeptides?
Quaternary
Calculate the minimum number of DNA bases needed to code for the number of amino acids in one alpha polypeptide. (1)
423
Describe the role of haemoglobin in supplying oxygen to the tissues of the body. (2)
- haemoglobin binds/associates with oxygen in an area of higher partial pressure of oxygen (lungs)
- oxygen is released/dissociates in areas of lower partial pressure of oxygen (tissues)
Explain how oxygen is loaded, transported and unloaded in the blood. (6)
- haemoglobin carries oxygen/has a high affinity for oxygen
- haemoglobin associates oxygen in the lungs
- at a high partial pressure of oxygen
- dissociates to respiring tissues/cells
- at a low partial pressure of oxygen
- unloads at a higher carbon dioxide concentration (due to LOWER pH).
Explain how the shape of a red blood cell allows it to take up a large amount of oxygen in a short time. (2)
- Large surface area to volume ratio = for diffusion
- flat/thin = short diffusion pathway
Explain how aerobic respiration in cells leads to a change in the pH of blood plasma. (2)
- CO2 is produced in respiration
- forms carbonic acid
What is the advantage to tissue cells of a reduction in the affinity of haemoglobin for oxygen when the plasma pH decreases?
- low pH due to a high rate of respiration (more CO2 produced)
- Cells need more O2
- More O2 released/released faster.
Where is oxygen loaded?
regions with a high partial pressure
Example of a region with high partial pressure:
alveoli
Where is oxygen unloaded?
regions with a low partial pressure
Example of a region with a low partial pressure:
respiring cells
At LOWER partial pressures, does haemoglobin have a higher or lower affinity for oxygen?
lower
At HIGHER partial pressures, does haemoglobin have a higher or lower affinity for oxygen?
HIGHER
What happens to hemoglobin’s affinity for oxygen when the dissociation curve shifts right?
affinity for oxygen decreases
