Unit 1 Topic 1BC Mammalian Transport System Flashcards
define diffusion
- free movement of particles in a liquid or a gas down a concentration gradient
- movement from area of particles in high concentration to relatively low concentration
what kinds of species can survive with diffusion
- single-celled organisms (amoeba)
- microscopic multicelular organisms (marine larvae)
why is diffusion sufficient for single-celled organisms / microscopic multicellular organisms
- small diffusion distance from outside to innermost areas of cells
- small organism = large surface area to volume ratio = larger surface area for diffusion
- low metabolic demands (do not regulate own temperature, do not use much oxygen, food)
define mass transport system
- arrangement of structures by which substances are transported in the flow of a fluid with a mechanism for moving it around the body
- overcome the limits of diffusion between the internal and external environments
- delivered over short distances from the mass transport system to individual cells by processes (diffusion, osmosis, active transport)
features of a mass transport system
1.Exchange surfaces to get materials into and out of the transport system
2.System of vessels that carry substances (tubes, specific routes, widespread and branching)
- Make sure substances are moved in the right direction (nutrients in and waste out)
- Moving materials fast enough to supply the need of the organism (mechanical methods: pumping of the heart)
3.Suitable transport medium (fluid)
- Adapting the rate of transport to the needs of the organisms
why do multicellular animals require mass transport system
The need for transport in multicellular animals: Chemical substances be transported into or removed from cells or moved around the body
- Requires glucose and oxygen for cellular respiration
- Produces toxic waste product carbon dioxide = removed before causing damage
- Chemicals made in a cell of one part of body: hormone ⇒ insulin / adrenaline
Explain how haemoglobin acts as a pH buffer in blood during the transport of carbon dioxide
- Carbon dioxide reacts with water in the cytoplasm of red blood cells to form carbonic acid
- Reference to carbonic anhydrase
- Carbonic acid dissociates into hydrogen ions and hydrogencarbonate ions
- Hydrogen ions bind with haemoglobin to form haemoglobinic acid
- This reduces the amount of hydrogen ions that lower the pH of blood
Describe how the aorta is adapted to accommodate sudden increases in the blood flow
- Elastic fibres in the aorta can stretch when blood flow into the aorta suddenly increases
- The lumen of aorta widens
- The wall of aorta contains collagen to increase the strength
What mainly provides for the main force of blood flow in veins
- Contraction of skeletal muscles lying next to veins
- Skeletal muscles lying next to veins contract
- Veins are being squeezed
- Volume of part of veins being squeezed decreases -> blood pressure inside that part of veins increase -> force semi-lunar valves open
- Backflow of blood is prevented by closure of valves (blood pressure up > blood pressure down)
- Blood forced to flow toward heart
Outer layers of arteries and veins
Outer layer: fibrous tissue -> maintain blood vessel wall structure
Properties of the middle layer of arteries and veins
Middle layer: smooth muscles, thick wall, elastic tissues (arteries thicker)
- smooth muscles: contraction and relaxation can cause constriction and dilation of blood vessel
- thick wall: withstand high blood pressure due to pumping action of heart
- elastic tissues: distend and recoil to maintain a continuous blood flow under high blood pressure through the arteries -> diminish fluctuations of blood pressure
Properties of inner layer of arteries and veins
Inner layer: endothelium -> provide a smooth surface for rapid flow of blood over its surface with little resistance
-> arteries have a smaller lumen than veins
Properties of capillaries (7)
- Differentially permeable
- Numerous branches of capillary network penetrate tissue
- One-cell thick endothelium wall
- Network highly branched
- Large total cross-sectional area
- Diameter slightly larger than that of red blood cells
- Presence of gaps between endothelial cells of walls of capillary
Properties of coronary artery
- Supplies oxygen and nutrients (e.g. glucose) to cardiac muscle -> undergo respiration to release energy for muscle contraction
- Contains myoglobin
Define and state the function of myoglobin
a respiratory pigment that has stronger affinity for oxygen than haemoglobin-> stores oxygen for respiration, producing energy for heart muscles to contract
State the process of blood clotting
- Thromboplastin catalyzes the conversion of prothrombin (large soluble protein) found in blood all the time
- Prothrombin is converted to thrombin, a soluble enzyme, in the presence of calcium ion. Prothrombin is a biologically inactive precursor of biologically active thrombin
- Thrombin catalyzes the conversion of fibrinogen (fibrous soluble plasma protein) to fibrin (fibrous insoluble protein). Fibrinogen is a biologically inactive precursor of biologically active fibrin
- Fibrin forms a mesh of fibres to cover the wound
- More platelets and red blood cells gets trapped in fibrin mesh, forming a clot
It is possible to reduce the risk of CVD by taking medication or changing diet. Explain the role of antihypertensive drugs
- Antihyperintensive drugs lower blood pressure
- Lower blood pressure reduces risk of damage to endothelium of the artery
- Reduced risk of inflammatory response
- Reduced risk of {atheroma / plaque} formation
Explain how a change in the primary structure of Factor VIII (an enzyme that is involved in the process of blood clotting) could cause difficulties with blood clotting
- Different primary structure -> different sequence of amino acids
- Change in R groups changes tertiary structure
- Changing shape of active site prevents substrate from being able to bind
- Reducing production of fibrin
The baby survived because of a hole in the septum of the heart. Explain how the hole in the septum allowed this baby to survive.
- The hole allows oxygenated and deoxygenated blood to mix (between the two ventricles)
- Oxygenated blood {travels to the body / enters aorta} / deoxygenated blood {travels to the lungs / enters pulmonary artery}
- Providing some oxygen for respiration
How human lungs are adapted for efficient gas exchange
- Fick’s law suggests that the diffusion rate is proportional to the surface area
1.Lungs contain large number of highly folded alveoli which are
- Covered with a dense network of blood capillaries
- Increases the surface area for gas exchange by diffusion
2.Dense network of capillary has a continuous flow of oxygenated blood to and deoxygenated blood away from the alveoli
- Maintaining a steep concentration gradient
3.Alveolar and capillary walls are one cell thick
- The walls are made from a single layer of endothelial cells
- Provides a short distance for diffusion of gases
- increase rate of diffusion
- These features increase the gas exchange by diffusion of oxygen and carbon dioxide between alveoli and blood in surrounding capillaries
Why multicellular animals require a respiratory and circulatory system
- Relatively small SA to volume ratio
- Diffusion on body surface is not enough because
- Gas exchange by diffusion is too slow to supply oxygen and remove carbon dioxide from all body cells
- A respiratory system provides a larger SA to compensate for the smaller SA: V ratio
Why smaller animals do not need a specialized gas exchange system
- Small body size, so it has low activity
- It has a large SA:V ratio so
- Distance between body surface and innermost body cells/parts are short
- Hence gas exchange by diffusion alone is sufficient to provide oxygen for respiration of cells to produce energy for metabolic need.
Suggest how double circulation enables mammals to carry out effective gas exchange
- Double circulatory system separates oxygenated and deoxygenated blood
- Ensures deoxygenated blood delivers to alveoli for gas exchange
- Oxygenated blood is delivered to body cells
- Maintaining the steep concentration gradient for effective gas exchange
- Ensures different pressures in the heart. Blood pumps at a lower pressure to the lungs to prevent the alveoli from being damaged.
How does the structure of haemoglobin cause S oxygen dissociation curve
- Haemoglobin composed of four subunits
- Binding of the first oxygen molecule is difficult but
- Binding of the other molecules becomes easier and there is cooperative binding
- Due to a conformational change
- As haemoglobin becomes saturated less oxygen can bind so the curve flattens out
Why percentage saturation of haemoglobin in a person with high altitude is lower than a person at sea level
- Partial pressure of oxygen in the atmosphere at high pressure is lower than at sea level
- Therefore partial pressure of oxygen in the alveoli will be lower
- The concentration gradient between alveoli and blood will be smaller
- Rate of diffusion of oxygen into the blood will be slower
- Haemoglobin will not be able to bind to as much oxygen
Why oxygen dissociation curve of adult haemoglobin is different from fetal haemoglobin
- Oxygen dissociation curve for adult haemoglobin is shifted to the right of curve of fetal haemoglobin
- Because oxygen needs to diffuse from maternal blood to fetal blood
- Therefore fetal haemoglobin needs to have a higher affinity for oxygen
Explain why an organism doesn’t need blood vessels to transport blood around
- It has a small body size and large surface area to volume ratio
- All cells are close to blood
- It has a low metabolic rate
- Transport of substance by diffusion is sufficient and blood vessels are not necessary.
Explain why animals need a heart and circulatory system
- Animals have a low surface area to volume ratio
- It has a high metabolic rate
- Transport of substance by diffusion alone is insufficient
- Animals need a heart to generate enough blood pressure to supply oxygen and nutrients to circulate around the body by mass flow
- Animals need capillaries to ensure that all parts of the body are close to blood supply
Explain the difference in thickness of the wall of right atrium and wall of right ventricle
- Wall of right ventricle is thicker as there are more muscles in the right ventricle
- The thicker muscle walls allow the right ventricle to produce stronger muscle contraction
- To generate greater pumping force to pump blood out of the right ventricle to allow blood to travel at a longer distance to the lungs
- While the right atrium only pumps blood to the right ventricle
Explain the difference between left ventricle and right ventricle
- Left ventricle has a higher maximum kPA than right ventricle
- Because the left ventricle is more muscular than the right ventricle and has to generate stronger muscle contraction to generate greater pumping force
- To pump blood out of left ventricle through the aorta to the rest of the body at a greater distance
- While the right ventricle only pumps blood to the lungs
- If blood pumped is under high pressure in the right ventricle, there would be damage to the lungs
Myogenic
- Characteristic of cardiac muscle where
- It can initiate its own contractions without the need for nervous stimulation
Why the mammalian heart is divided into a right side and a left side
- Separates oxygenated and deoxygenated blood
- Ensures deoxygenated blood delivers to alveoli for gas exchange
- Oxygenated blood is delivered to body cells
- Maintaining the steep concentration gradient for effective gas exchange
- Ensures different pressures in the heart. Blood pumps at a lower pressure to the lungs to prevent the alveoli from being damaged.
Explain why there is a slight decrease in the left atrium pressure before the semilunar valves close
- Aorta wall has large amount of elastic fibres
- Aorta wall stretch to withstand high blood pressure
- Hence blood pressure decreases slightly
- Aorta wall recoil to maintain high blood pressure, hence blood pressure increases
Explain how blood clot can cause a heart attack (myocardial infarction)
- Blood clots block the coronary arteries
- Oxygenated blood is prevented from reaching heart muscle
- Preventing aerobic respiration and resulting in anaerobic respiration
- Cardiac muscles unable to contract as cardiac cells die.
Explain how blood clotting can cause stroke
- Reduced oxygenated blood flow to the brain
- Less aerobic respiration occurs to provide energy and ATP for brain cells
- Brain needs ATP to function
- Lactic acid produced from anaerobic respiration
- Which is toxic and inhibits enzymes, causing the brain cells to die.
- Brain muscles die causing a stroke
Consequences of faulty AV valve
- Backflow of blood from the ventricles to atria during ventricular systole
- Blood pressure is lowered and the supply of oxygen is less efficient
- Also blood pressure in lungs increase
- So may feel tired and breathless
Suggest how the location of atheroma results in position and size of region of dead heart muscle
- The higher the region of atheroma in the blood vessel, the larger the size of the region of dead heart muscle
- Because less oxygenated blood can reach the heart muscles to provide oxygen for aerobic respiration in cells, so the cells die due to a lack of energy
Explain how atherosclerosis develops
- Blood pressure increases, the endothelium of artery is damaged
- Leading to an inflammatory response
- Atheroma builds up on the endothelium and
- Hardens as calcium and fibrous tissues build up, leading to atherosclerosis
- The endothelium becomes less elastic and the lumen narrows
- The process is self-perpetuating.
Explain the effects on the heart function after the coronary artery becomes blocked
- Less blood reaches the heart muscle cells,
- Muscle cells are not supplied with enough oxygen and glucose
- Aerobic respiration decreases
- Anaerobic respiration occurs and lactic acid is produced
- Lactic acid lowers pH and denatures enzymes
- Anaerobic respiration produces much less ATP and energy
- Less blood is pumped to the heart
Describe how the development of atherosclerosis can lead to CVD
- High blood pressure increases the damage to the endothelium of arteries
- There is an inflammatory response and plaque deposits on arterial wall
- Calcium and fibrous tissue build up causing the plaque to harden, causing atherosclerosis
- Hence the lumen narrows and the arterial wall loses elasticity
- The blood supply to tissues is reduced and tissues receive less oxygen
- So there may be myocardial infarction
Explain how blood pressure increases the risk of developing CVD
- When BP is higher, the risk of damage to the endothelium of arteries is higher.
- There is an inflammatory response
- Leading to the formation of atheroma and atherosclerosis develops
- Also increases the risk of blood clot formation
- The lumen is further narrowed and the arterial wall is less elastic
- Blood pressure further increases and the risk of CVDs increase
Risk of high-fat diet and low activity levels in CVD
- Energy imbalance and energy intake is higher than energy expenditure
- Individual may become obese and blood pressure is raised
- Endothelium of arteries likely to be damaged, causing an inflammatory response and cholesterol build up on arterial wall, atheroma forms and atherosclerosis when the atheroma hardens
- Hence the arterial wall loses elasticity and the lumen is narrowed
- Obesity increases the risk of diabetes, which is a risk factor of CVD
- Hence the blood cholesterol increases and the HDL:LDL ratio is lowered, increasing the risk of CVD
How to reduce risks in CVD
- Reduce energy intake: weight and BMI decreases if energy expenditure is greater than intake
- Reduce cholesterol levels in diet: cholesterol is associated with high blood pressure and atherosclerosis
- Reduce saturated fats: reduces blood cholesterol
- Increase exercise: reduces blood pressure/ maintain healthy heart/ weight and BMI decrease if energy expenditure is greater than intake
- Stop smoking (if): Smoking increases blood pressure/ increases risk of atheroma
- Reduce salt in diet
- Reduce alcohol intake
How does wafarin work
- Interfere with prothrombin formation
- Reduce the risk of blood clot formation
- Reducing the risk of thrombosis and artery blockage ( Risk: internal bleeding )
- Hence maintain oxygen supply to tissue
- The risk of heart attack and stroke decreases
Risks of warfarin
Risks of warfarin:
- Could bleed internally, particularly in brain -> careful monitoring to ensure clotting of blood is reduced but not prevented completely
- Consider age condition and any other medication taken
How does aspirin work
E.g. aspirin
- Make platelets less sticky
- Reducing the risk of formation of blood clot in the blood vessel
- Decrease the risk of having thrombosis and stroke
How does antihyperintensives: beta blockers work
- Prevent response of heart to hormones (e..g adrenaline -> increases heart rate and blood pressure)
- Cause heart rate to be slower and blood pressure to be lower
Define sympathetic nerves
set of nerves that transmit nerve impulses from centrol nervous system to all parts of body
How does Sympathetic Nerve Inhibitors work
- Prevent sympathetic nerves from signalling arteries to contract
- Arteries remain dilated
- Lowers blood pressure
What is ACE inhibitors
–> ACE inhibitors
- Angiotensis (produced in liver) stimulates constriction of arterioles -> blood pressure rises
- Type of vasodilator drug that blocks production of angiotensis
- Keeps arterioles dilated -> blood pressure can be kept lower
How does statins lower blood cholesterol level
- By blocking enzyme in liver which is needed to catalyze synthesis of cholesterol
- By blocking production of LDLs
How does statin reduce risk of atherosclerosis
- blocking the production of LDLs
- reduce risk of atheroma formation
- reduce inflammation in smooth endothelial lining of arteries -> risk of developing atherosclerosis is reduced
What is the side effect of statin
constipation, muscle and joint aches, diabetes, insomnia
What are some warnings or suggestions to people who take statin?
A healthy diet should be taken as statins give no protection against other ill effects of a diet that is high in fats and cholesterol
Explain how dietary antioxidants reduce the risk of CVDs
- Antioxidants reduce free radicals
- Free radicals damage cells, tissues and endothelial lining of blood vessel
- Hence antioxidants reduce cell damage
- Antioxidants reduce formation of atheroma and atherosclerosis
- Reducing the risk of CVD
Active inhalation (how it draws air into the lungs)
- External intercostal muscles and the diaphragm muscles contract
- Contraction of external intercostal muscles causes the rib cage to move upwards and outwards
- Contraction of the diaphragm muscles causes the diaphragm to be lowered and flattened
- Resulting in an increase in volume, decrease in pressure of the chest cavity
- The pressure of the lungs is greater than the pressure of the chest cavity, causing the lungs to expand.
- Volume of the lungs increases, air pressure decreases, air pressure in lung lower than atmospheric pressure
- Air is drawn into the lungs through the airways
Passive exhalation
- External intercostal muscles and the diaphragm muscles relax
- Relaxation of the external intercostal muscles causes the rib cage to move downwards and inwards
- Relaxation of the diaphragm muscles causes the diaphragm to recoil to a dome shape
- Resulting in a decrease in volume, increase in pressure of the chest cavity
- The pressure of the chest cavity is greater than the pressure of the lungs, causing the lungs to deflate due to its elasticity
- Volume of the lungs decreases, air pressure increases, air pressure higher than atmospheric pressure
- Air is forced out of the lungs through the airways
Forced exhalation
- Internal intercostal muscles and abdominal muscles contract
- Contraction of the internal intercostal muscles causes the rib cage to move downwards and inwards
- Contraction of the abdominal muscles causes the diaphragm to move upwards
- Resulting in a decrease in volume, increase in pressure of the chest cavity
- The pressure of the chest cavity is greater than the pressure of the lungs, causing the lungs to deflate due to its elasticity
- Volume of the lungs decreases, air pressure increases, air pressure is higher than the atmospheric pressure
- Air is forced out of the lungs through the airways
Open vs closed circulatory system
Open
- Blood circulates in open spaces in body and baths body cells
Closed
- Blood circulates within blood vessels
- Blood flows at a higher pressure and
- Blood flow is directed precisely to different organs with different demand of oxygen and nutrients
Explain the Lub sound in Lub and dub
- LUB is due to ventricular systole.
- As ventricular pressure increases to be higher than the atrial pressure, the atrioventricular valves are forced shut
- LUB sound occurs when there is a backflow of blood that hits the atrioventricular valves when the ventricles contract
Explain the Dub sound in Lub and Dub
- DUB is due to diastole
- As ventricular pressure decreases to be lower than the pressure of the aorta and the pulmonary artery, the semilunar valves are forced shut
- DUB sound occurs when there is a backflow of blood that hits the semilunar valves when the ventricles relax.
Red blood cell features
1.Biconcave disc shape provides a large surface area to volume ratio
- Speeding up the rate of diffusion such that
- Oxygen can diffuse into and out of red blood cells rapidly, speeding up oxygen transport
2.Mature erythrocytes do not have a nucleus
- Increase space to accommodate for more haemoglobin such that
- More oxygen can be carried
3.Contain haemoglobin
- Which can carry oxygen around the body by forming oxyhaemoglobin
Explain the Bohr shift
- Describe changes in oxygen dissociation curve as a result of increased carbon dioxide levels in blood
= Haemoglobin gives up oxygen more readily to respiring tissues when it is needed
Why do haemoglobin give up oxygen more readily to respiring tissues when it is needed?
-> Removal of CO2 of body cells and uptake of O2 by body cells: in respiring tissues where cells produce carbon dioxide due to respiration
What is the relationship between the pH of blood and release and oxygen
- Lowers pH of blood:
- CO2 combines with water -> carbonic acid
- Carbonic acid dissociates into hydrogencarbonate ions and hydrogen ion
- Hydrogen ion binds to haemoglobin, causing release of oxygen
CO2 transport in blood
- Carbon dioxide dissolves in the blood plasma (5%)
- Carbon dioxide binds with haemoglobin to form carbaminohaemoglobin (10-20%)
- Carbon dioxide reacts with water to form carbonic acid, catalysed by carbonic anhydrase CAH
- Carbonic acid dissociates into hydrogencarbonate ions and hydrogen ions
Define and explain LDLs
LDLs are low-density lipoproteins
- Made from saturated fats, cholesterol and protein
- Bind to cell membrane before being taken into cell
- High levels can make cell membranes saturated, causing higher blood cholesterol levels
Define and explain HDLs
HDLS are high-density lipoproteins
- Made from unsaturated fats, cholesterol and protein
- Carry cholesterol from body tissues to the liver to be broken down, lowering cholesterol levels
- Can help remove cholesterol from fatty plaques in arteries
Antihypertensives: Diuretics
- Eliminates excess fluids and salts in urine
- Volume of urine produced increases
- Blood volume decreases
- A smaller volume of blood can be pumped from the heart
Blood pressure decreases
Benefits of antihypertensives
- Lowering of blood pressure -> risk of CVD + risk of damage to kidneys and eyes due to high pressure reduced
Risks of antihypertensive
- Blood pressure too low: dizzy and may fall easily due to decreased rate of respiration of brain cells -> injuries that might be life-threatening
Side effects of antihypertensive
Side effects: coughs, swelling of ankles, tiredness and fatigue, constipation
Oxygen dissociation curve (how curve changes as oxygen binds to haemoglobin)
1.Shape of hemoglobin is difficult for first oxygen molecule to bind to it
- Binding of first oxygen occurs slowly; shallow curve at the bottom left corner
2.After first oxygen molecule binds to hemoglobin, the shape of hemoglobin protein undergoes conformational change, making it easier for the next oxygen molecule to bind to hemoglobin (cooperative binding)
- Speeds up binding of remaining oxygen molecules; steeper part of curve in the middle
3.As hemoglobin molecule approaches saturation, it takes longer for the 4th oxygen molecule to bind due to the shortage of remaining binding cites
- Levelling off of curve in the top right corner; gets progressively harder to remove oxygen
What is angina
- Plaques build up in coronary arteries
- Narrowed coronary arteries cannot supply enough oxygenated blood -> anaerobic respiration (breakdown of glucose in absence of oxygen)
- cells can no longer contract (less elastic artery), reducing force generated by heart when it beats
- cells can die -> permanent damage to heart tissue -> myocardial infarction
Symptoms of angina
gripping pain in chest, breathlessness, sweating
How to reduce symptoms of angina by daily habits
regular exercise, lose weight, quit smoking, help of drug
Suggest two treatments for angina
- Stent insertion (+ angioplasty - balloon to inflate stent) - stent inserted into coronary arteries to hold them open
- Coronary bypass - a piece of blood vessel from patient is used to create a new passage for flow of blood to cardiac muscle and bypass blocked area
What is aneurysms
- area of artery is narrowed by plaque
- blood is collected behind the blockage
- artery bulges and the wall is weakened due to a higher blood pressure than usual
- weakened artery may split open -> internal bleeding
- Frequently happens in the blood vessels that supply brain with blood or in aorta
How deoxygenated blood travels through heart
- Inferior vena cava receives deoxygenated blood from lower parts of the body, while superior vena cava receives deoxygenated blood from head, neck arms and chest. Thus, deoxygenated blood enters right atrium
- As blood enters the right atrium, blood pressure increases, forcing open tricuspid valves
- The right ventricle is gradually filled with blood
- When the right atrium is filled with blood, its wall contracts, causing the right ventricle to be filled with more blood under pressure
- When the right ventricle is filled with blood, its wall contracts, forcing blood into pulmonary arteries. The blood will lead to capillaries in the lungs.
- As the blood pressure inside the right ventricle is higher than inside the right atrium, the tricuspid valve closes to prevent backflow of blood from right ventricle to left artium.
- When the wall of the right ventricle relaxes, the blood pressure in the right ventricle become lower than that in the pulmonary artery. Thus, the semilunar valves close to prevent blood flowing from the pulmonary artery into right ventricle
How oxygenated blood enters the heart
- Oxygenated blood from lungs enter the left artium via pulmonary vein
- As the left artium is filled with blood, blood pressure inside increases, forcing open bicuspid valve, causing blood to enter left ventricle
- When the left atrium is filled with blood, its wall contracts. The left ventricle is filled with more blood under pressure
- When the left ventricle is filled with blood, its wall contracts, forcing blood into aorta and out of heart
- As blood pressure inside left ventricle is higher than that of left atrium, the bicuspid valve closes to prevent backflow of blood from left ventricle to left artium
- When the left ventricle relaxes, the blood pressure inside the left ventricle becomes lower than that in the aorta, so the semilunar valves close to prevent backflow of blood from aorta to left ventricle
Which components of blood clotting process are enzymes in their active form?
thrombin and thromboplastin only
Which components of the blood clotting process are soluble in blood plasma?
fibrinogen and thromboplastin
One type of drug that can prevent stent thrombosis
Anticoagulant / Platelet inhibitors
Explain why very thick, sticky mucus results in breathing difficulties, problems absorbing nutrients and infertility (5)
1.because the mucus blocks the airways (1)
- therefore {air flow to lungs / gas exchange} is reduced (1)
2.because mucus prevents pancreatic enzymes from entering the small intestine (1)
- therefore large food molecules not broken down (and cannot be absorbed) (1)
3.because the mucus prevents sperm passing through the cervix (1) * therefore sperm cannot reach the egg cell (1)
Correlation vs causation
Correlation: when a change in one variable is reflected by a change in another variable
Causation: Change in one variable is responsible for another variable
Blood leaves the heart through the arteries. Compare and contrast the structure of the aorta with the structure of the pulmonary artery.
Similarities:
- both have walls containing {muscle cells / elastic fibres / an endothelial cell lining / an (outer) collagen layer} (1)
- both have a valve (at the point they leave the heart) (1)
Differences:
- aorta has a {lumen with a wider diameter / thicker wall / more elastic tissue / more muscle tissue / more collagen} (1)
- aorta has branches to more organs (1
Explain why the oxygen dissociation curve of adult haemoglobin is different than that of fetal haemoglobin.
- oxygen dissociation curve for {maternal / adult} Hb is shifted to the right of curve for fetal Hb (1)
- because oxygen needs to diffuse from {maternal / adult} blood into fetal blood (1)
- therefore fetal haemoglobin needs to have a higher affinity for oxygen (1)
Explain how dietary antioxidants reduce the risk of CVD. (3)
- because antioxidants reduce free radicals (1)
- free radicals cause {cell damage /tissue damage / oxidative stress / damage to endothelial lining} (1)
- (antioxidants) reduce {plaque / atheroma} formation (1)
What is cardiac muscle and its properties
- thick muscular layer
- myogenic: contract and relax without nervous or hormonal stimulation
- never fatigues: as long as supply of oxygen / glucose
What are coronary arteries
- supply cardiac muscle with oxygenated blood
- branch off from aorta
What happen when coronary artieries are blocked
- myocardial infarction (heart attack)
- cardiac muscle will not receive oxygen
- will not be able to respire
- cardiac muscle cells will die
Why is the muscle in atrium thinner than ventricle
- thinner muscular walls
- do not need to contract as hard as not pumping blood far (only to ventricles)
Features of atria
- thinner muscular walls
- elastic walls to stretch when blood enters
Why are there thicker muscular walls in ventricles
- bigger contraction
- higher blood pressure
- enable blood to flow longer distances (to lung and rest of the body)
Why does the right ventricle have a thinner muscular wall than the left ventricle
right ventricles
- pumps blood to the lungs
- needs to be at a lower pressure to prevent damage to capillaries in the lung
- blood flows slowly = allows time for gas exchange
left ventricle
- pumps blood to the body
- higher pressure to ensure blood reaches all cells in body
- thicker muscular wall
- larger contractions of the muscle to create higher pressure
Vena Cava
- carries deoxygenated blood from the body into the right atrium
Pulmonary vein
- carries oxygenated blood from lungs to the left atrium
Pulmonary artery
- deoxygendated blood from right ventricle to the lungs to become oxygenated
aorta
- carries oxygenated blood from left ventricle to the rest of the body
semi-lunar valves
- aorta and pulmonary artery
atrioventricular valves
- between atria and ventricles
- left: bicuspid
- right: tricuspid
Function of septum
- separates the deoxygenated and oxygenated blood
- maintains high concentration of oxygen in oxygenated blood to maintain concentration gradient to enable diffusion at respiring cells
What is diastole
- atria and ventricular muscles are relaxed
- blood enter atria via vena cava, pulmonary vein
- blood flowing into atria increases the pressure within atria
What is atrial systole
- atria muscular walls contract
- volume decrease, increasing pressure
- causes antriovenricular valves to open and blood to flow into ventricles
- ventricular muscular walls are relaxed (ventricular diastole)
What is ventricular systole
- ventricle muscular walls contract
- volume decrease, increasing pressure
- cause atrioventricular valvues to close
- cause semi-lunar valves to open
- blood pushed out of the ventricles into the arteries (pulmonary and aorta)
What is cardiac output
- volume of blood which leaves one ventricle in one minute
- = heart rate (bpm) x stroke volume (dm3)
What happens to the volume of atria throughout the cardiac cycle
atrial systole: decreases
ventricle systole: no change
diastole: increases
What happens to the pressure in artria throughout the cardiac cycle
atrial systole: increases
ventricle systole: no change
diastole: increases
What happens to the volume of ventricles throughout the cardiac cycle
atrial systole: increases
ventricle systole: decreases
diastole: slow increases
What happens to the pressure of ventricles throughout the cardiac cycle
atrial systole: decrease
ventricle systole: increase
diastole: slow increase
Why are capillaries differentially permeable
let small substances like glucose and metabolic waste pass through
Why do capillaries have numerous branches of capillary network penetrate tissue
shorten distance for diffusion materials between blood and body cells
Why do capillaries have one-cell thick endothelial wall
short distance for rapid diffusion of materials between blood and body cells
Why are the capillaries network highly branched
provide larger surface area to volume ratio for rapid exchange of materials between blood and body cells
Why do capillaries have a large total cross-sectional area
lowest rate of blood flow -> provide more time for exchange of materials between blood and body cells
Why do capillaries have a diameter slightly larger than red blood cell
allows blood to travel relatively slowly through capillaries -> longer time for diffusion of materials between blood and body cells
Why are there presence of gaps between the endothelial cells of walls of capillaries
allows white blood cells to change shape and squeeze through gaps between endothelial cells of capillary walls -> reach infected body cells
(past paper: spec) Explain the differences between the dissociation curves of llama and human. (4)
- dissociation curve of llama is left of that for human (explain the diagram first)
- llama haemoglobin has higher affinity for O2
- llama haemoglobin is fully saturated with oxygen at lower partial pressures
- because less oxygen available in atmosphere at high altitudes
Explain the process of blood clotting
takes place to reduce blood loss and prevent pathogens from entering thorugh injury
- platelets come in contact with damaged blood vessel and change shape to spherical shapes
- clump together to form temporary plug
- platelets released thromboplastin, a double enzyme that catalyses conversion of prothrombin to thrombin
- thrombin catalyses fibrinogen into insoluble fibrin fibres that form a mesh that trap more blood cells to form a clot
Oxygen partial pressure and oxygen affinity
oxygen affinity varies depending on oxygen partial pressure
- in lungs, high PP of O2 so loads more readily
- in tissue, low PP of O2 so decreases, unloads oxygen
Properties of capillary
- made of one layer of endothelial cells
Features of artery
- collagen fibres (pressure)
- muscle, elastic fibres (volume, contraction, relaxation)
- endothelial lining cells
- folded inner lining to avoid damage, allow for stretching (withstand high blood pressure, prevent bursting)
Features of vein
- collagen for strength + structure
- less smooth muscle, as no need to contract
- little elastin, low pressure
- endothelium
(past paper: Jan19) Explain the changes in the internal diameter of the aorta during two cardiac cycles (3)
- increases in diameter due to high pressure / large volume / surge of blood leaving the left ventricle
- therefore expansion of elastic fibres
- decrease in diameter due to recoil of elastic fibres
(past paper: Jan19) Explain why the risk calculator takes into account total cholesterol and HDL cholesterol levels. (2)
- because there is a ink between total blood cholesterol levels and heart disease
- because HDL is not thought to be a risk factor, LDL is associated with development of heart disease, LDL:HDL determines level of risk
(past paper: Jan19) Explain why the value obtained for the 10 Year CHD Risk may be an underestimate (3)
- there are other risk factors that are not included
- because people will underestimate their mass / how much they smoke
- because total cholesterol /HDL / blood pressure might be an estimate
(past paper:Jan19) Describe how the movement of phosphatidylserine into the outer layer results in the production of thrombin in the blood clotting process (4)
- thrombin is an enzyme
- inhibitor will change the shape of the active site
- thrombin cannot bind to fibriinogen
- less fibrinogen will be converted into fibrin
- there is less mesh to trap blood cells
Partial pressure of oxygen in air in the alveoli is lower than in atmosphere
- Water vapour and carbon dioxide added to air
- Oxygen used by cells in respiration
- Oxygen moves into capillaries
Partial pressure of oxygen decreases as blood flows through arteries into veins
- Arteries take blood to cells and veins take blood away from cells
- Oxygen diffuses out of the capillaries into the cells
- Because there is a lower partial pressure in cells
- Carbon dioxide is entering the blood
Why percentage saturation of haemoglobin in a person at high altitude is lower than person at
sea level
- Partial pressure of oxygen in the atmosphere at high pressure is lower than at sea level
- Therefore partial pressure of oxygen in the alveoli will be lower
- The concentration gradient between alveoli and blood will be smaller
- Rate of diffusion of oxygen into the blood will be slower
- Haemoglobin will not be able to bind to as much oxygen
Features of amino acids located on outer surface of haemoglobin
- Must have R groups that are polar
- So that the haemoglobin can dissolve in red blood cell, cytoplasm and water
Explain why animals need a heart and circulatory system
- Animals have a low surface area to volume ratio
- It has a high metabolic rate
- Transport of substance by diffusion alone is insufficient
- Animals need a heart to generate enough blood pressure to supply oxygen and nutrients to
circulate around the* body by mass flow **** - Animals need capillaries to ensure that all parts of the body are close to blood supply
Describe circulation of blood in a fish
- Fish have a single circulatory system. Blood only passes through the heart once during the
cardiac cycle - Blood flows from heart to gills
- Then from the gills to the rest of the body
- Blood then flows from the rest of the body back to the heart
Compare human circulatory system with fish
- Humans have a double circulatory system while fish a single circulatory system
- Blood flows at a higher pressure to the body
- Blood flows at a lower pressure to the lungs
- THis decreases the risk of damage to the lungs
- Allows transport of gases to be more efficient
Why butterfly has different circulatory from human
- Butterfly does not have a double and closed circulatory system
- Butterfly is small so cells are not far from the blood
- So diffusion can supply the oxygen from the blood
- Butterfly has a low metabolic rate
- Transport of substance by diffusion can supply oxygen from blood
Suggest differences between fibrinogen and fibrin
- Fibrinogen is soluble while fibrin is insoluble
- Fibrin is fibrous while fibrinogen is globular
- Fibrinogen and fibrin have different sizes
Enzymes and proteins present in blood clotting process
- Thromboplastin, prothrombin, thrombin are enzymes
- Fibrinogen, fibrin are proteins
Structure of Capillaries
- Capillaries have one layer of squamous epithelial cells/ one cell thick endothelium to
- Shorten diffusion distance between blood and body cells
- Capillaries have pores/ gaps between cells
- To facilitate the exchange of materials
Structure of Aorta
- Elastic fibre (ref above)
- Collagen in the wall give wall tensile strength so it can withstand high pressure and avoids the
artery from rupturing - Semilunar valves at the start of the aorta prevents the backflow of blood during diastole
Structure of Artery / Aorta
- Elastic fibres which can stretch and recoil to maintain blood pressure
- Smooth muscle which contract to reduce size of lumen
- Smooth endothelium reduces friction when blood passes through the lumen
- Narrow lumen to maintain high blood pressure
- Folded endothelium which allows stretching to accommodate higher pressure
- Collagen in the wall give wall tensile strength so it can withstand high pressure and avoids the
artery from rupturing
Difference between artery and capillaries
- Arteries have elastic fibres but capillaries don’t
- Arteries have collagen fibres but capillaries don’t
- Arteries do not have pores but capillaries have pores
- Arteries have a thick muscle wall but capillaries have a one cell thick wall (endothelium)
- Arteries have a narrow lumen but capillaries have a narrower lumen which is one cell wide
Difference between vein and capillaries
- Veins have valves but capillaries do not (NOT semilunar)
- Veins have collagen fibres but semilunar valves do not
- Veins do not have pores but capillaries have pores
- Capillaries have one cell thick wall while veins do not.
- Capillaries have narrower lumen than vein
Describe the role of heart valves in the cardiac cycle
- During the atrial systole when the atria contract,
- The atrioventricular valves open so blood flows from the atria to ventricles
- During the ventricular systole when the ventricles contract
- The semilunar valves open so blood flows from the ventricles to the aorta or pulmonary artery
- During the diastole, the ventricles relax, and semilunar valves close
- To prevent backflow of blood from aorta to the left ventricles and from the pulmonary artery to the
right ventricle
Explain why the changes in pressure that occur in the left atrium and the left ventricle are different. (5)
- The pressure changes are greater in the left ventricle than the left atrium
- The maximum ventricular pressure is 14.5 kPa which is 11.1 kPa greater than the maximum
atrium pressure (3.4 kPa) - This is because there are more cardiac muscles in the left ventricle.
- The thicker muscles allow the ventricles to have stronger muscle contraction to pump blood at a
higher pressure to longer distances - Also the atrial systole happens before the ventricular systole for the ventricle to fill with blood
- An increase in atrial pressure would cause ventricular pressure to increase
- Also when atrium pressure is greater than ventricular pressure, the atrioventricular valve opens
and prevents a further increase in atrium pressure.
Hole in septum (4 marks)
- Normally oxygenated and deoxygenated blood are separated by the septum
- But with a hole in the septum, the oxygenated and deoxygenated blood mix
- More oxygen flows into the lungs
- Resulting in a less steep oxygen concentration gradient in the alveoli
- There is less diffusion of oxygen from alveoli to blood capillaries
- Hence less oxygen to body cells
Hole in septum (2 marks)
- Oxygenated and deoxygenated blood mixes
- Less oxygen is delivered to the body and gas exchange is less efficient
- Systemic blood pressure is low.
Faulty AV valve
- Backflow of blood from the ventricles to atria during ventricular systole
- Blood pressure is lowered and the supply of oxygen is less efficient
- Also blood pressure in lungs increase
- So may feel tired and breathless
Explain the effects on the heart function after the coronary artery becomes completely blocked (New MS)
- Less blood reaches the heart muscle cells,
- Muscle cells are not supplied with enough oxygen and glucose
- Aerobic respiration decreases
- Anaerobic respiration occurs and lactic acid is produced
- Lactic acid lowers pH and denatures enzymes
- Anaerobic respiration produces much less ATP and energy
- Less blood is pumped to the heart
