Heart, Hb etc Flashcards
The cardiac cycle
ask
The ventricles relax whilst the atria contract.
- the contraction of the atria means a decrease in volume but an increase in the pressure. Because the ventricles at this moment are relaxed, the pressure in the atria exceeds the pressure in the ventricles so blood is pushed into the ventricles.
- there is a small increases in ventricular pressure and chamber volume as the ventricles receive the blood being ejected from the contracting atria
The ventricles contract whilst the atria relax
- the contraction of the ventricles means that chamber volume decreases but there is an increase in pressure. The pressure in the ventricles becomes higher than the pressure in the atria so the atrioventricular valves (tricuspid and bicuspid) are forced shut, preventing the back flow of blood.
- the pressure in the ventricles is higher than the pressure in the aorta (pathways after left ventricle) and pulmonary artery (pathway after right ventricle) so the semi lunar valves are forced open and blood flows into the aforementioned arteries.
The ventricles and atria both relax
- there is a higher pressure in the pulmonary artery and the aorta than in the ventricles (which are now relaxed) so the semi lunar valves are forced shut, preventing the back flow of blood into the ventricles.
- the blood flows out to the body (some to the body if it’s had its second pump and some to the lungs to get oxygenated if it still needs to return to the heart for its second pump)
- the blood returns to the heart and because there is a higher pressure in the vena cava and pulmonary vein (where blood is entering back into the heart from) than in the atria, it means that blood flows into the atria and they begin to fill again. This increases atrial pressure.
- whilst all this is happening the ventricles are still relaxing and as they relax their pressure falls until it becomes lower than the pressure in the atria which means that the atrioventricular valves open and blood flows passively into the ventricles from the atria.
- the process starts again so as I said before at the top of this flashcard, the atria contract (decreasing volume but increasing pressure) to squeeze the last bit of blood into the ventricles. CHECK: I don’t get it because the top of the flashcard is about blood flowing into the atria because of contracts and pressure but here it says that blood flows in passively when the process repeats???
MAYBE: the end of the process is passive when like as much blood is entering the ventricles as it passively can but the process restarts when the atria contract to push the blood that can’t passively flow into the ventricles!?
What has haemoglobin evolved to be like? (In terms of efficiency)
Efficient at loading oxygen in one se of conditions
Efficient at unloading oxygen in another set of conditions
Describe the structure of a haemoglobin molecule. (In terms of primary, secondary etc)
Primary - sequence of amino acids in 4 chains
Secondary - polypeptide chain folded into alpha helices and beta pleated sheets
Tertiary - polypeptide chain further folded into a precise shape
Quaternary - all 4 polypeptide chains linked together to form a spherical molecule.
What is each polypeptide chain of haemoglobin associated with?
Each polypeptide chain associated with a haem group that contains an Fe 2+ ion
Each Fe 2+ carries an oxygen
So each haemoglobin carries 4 oxygen molecules
What does the gene group allow haemoglobin to do?
Bind to oxygen
Haemoglobin bonding to oxygen is called
Loading or associating
Takes place in the lungs
Haemoglobin releasing oxygen is called
Unloading or dissociating
This takes place in the tissues
What does Hb with a high affinity for oxygen do?
Takes up oxygen more easily but releases it less easily
What does Hb with a low affinity for oxygen do
Takes up oxygen less easily but releases it more easily
How must Hb be efficient at the surface where gas exchange is occurring? (2)
- readily associate with oxygen at the surface where gas exchange takes place
- readily dissociate with oxygen at the tissues requiring oxygen
What is the important property of haemoglobin?
Give an example of what happens in a particular condition
It changes its affinity (chemical attraction) to oxygen under different conditions.
It does this by changing it’s shape in the certain conditions.
When there is lots of carbon dioxide the shape changes so that the Hb molecule binds more loosely to oxygen and as a result Hb LOSES (unloads) it’s oxygen
At the respiring tissues …. (oxygen conc, carbon dioxide conc, affinity of Hb for oxygen)
Oxygen conc is low
Carbon dioxide conc is high
So Hb has lower affinity for oxygen so it unloads oxygen
At the lungs gas exchange surface …. (oxygen conc, carbon dioxide conc, affinity of Hb for oxygen)
Oxygen conc is high
Carbon dioxide conc is low
Hb has high affinity for oxygen so oxygen loads on
What tends to differ about different organisms haemoglobin?
Haemoglobins have different affinities for oxygen
Why do different haemoglobin have different affinities for oxygen?
It’s due to the shape of the haemoglobin molecule
—> each haemoglobin has a slightly different tertiary and therefore quaternary structure so different oxygen binding properties. Depending on the structure of the Hb molecule they range from those with a high affinity for oxygen to those with a low affinity for oxygen.
At the respiring tissues …. (oxygen partial pressure, affinity of Hb for oxygen, Hb saturation)
Oxygen partial pressure is low
Hb affinity for oxygen is low
Hb saturation is low
At the lungs …. (oxygen partial pressure, affinity of Hb for oxygen, Hb saturation)
Oxygen partial pressure is high
Hb affinity for oxygen is high
Hb saturation is high
What does an oxygen dissociation curve show?
Relationship between the saturation of haemoglobin with oxygen and the partial pressure of oxygen
Describe the first part of the sigmoid oxygen dissociation curve
Shape of the Hb molecules makes it difficult for the first oxygen molecule to bind to one of the (Fe 2+?) in the heme group of one of the polypeptide chains (why?) because the chains are so closely united
At low oxygen concentrations little oxygen binds to haemoglobin.
Curve gradient is shallow
What does the binding of the first oxygen molecule to Hb mean?
Binding of first oxygen molecule changes the quaternary structure of the haemoglobin causing it to change shape. This change in shape makes it easier for the other sub units to bind to an oxygen molecule
Gradient of the curve steepens
(Hb alters it’s shape into the relaxed R state that has a higher affinity for oxygen)
Define positive cooperativity
Binding of the second oxygen molecule makes it easier for other subunits to bind more easily to an oxygen molecule
What does it mean for the increase in partial pressure of oxygen once the first oxygen molecule has bonded to Hb
It takes a smaller increase in partial pressure of oxygen for the second oxygen molecule to bind than it did for the first one.
First oxygen molecule binds after partial pressure of oxygen has increased a bit then because this alters shape of Hb partial pressure of oxygen doesn’t have to change much more until it becomes easier for the second oxygen molecule to bind
Describe how binding of the last oxygen molecule is affected by the binding of the third to Hb?
Binding of the fourth oxygen molecule is harder due to probability. Majority of binding sits occupied means it is less likely the oxygen will locate the last empty site to bind to.
Gradient goes to zero as curve flattens off but never fully reaches 100% Hb saturation
What does it mean if the oxygen dissociation curve is further to the LEFT
The greater the affinity of haemoglobin for oxygen
[loads oxygen more easily but unloads oxygen less readily]
(because Hb starts loading oxygen at lower oxygen partial pressures)
What does it mean if the oxygen dissociation curve is further to the RIGHT
The lower the affinity of Hb for oxygen
[loads oxygen less readily but unloads more easily]
(Because the Hb starts loading oxygen and saturation starts increasing only at higher oxygen partial pressures)
What does steep mean on the oxygen dissociation curve?
Loading of oxygen is easier
Unloading of oxygen is easier
What do shallow parts of the haemoglobin dissociation curve mean?
Harder for oxygen to bind
?what does it mean for unloading?
Harder for oxygen to unload because less carbon dioxide ?
What happens to the curve of oxygen affinity of Hb increases
Shifts left
Loading increases and obvs unloading decreases so less delivery of oxygen per gram of Hb
What causes increased affinity in Hb molecule?
A conformational or structural change in the Hb molecule
Usually eg. Brought about by first oxygen binding
What is the prosthetic group in haemoglobin?
Heme group
(Protoporphyrin ring with an Fe 2+ in the centre)
Fe 2+ has 4 single bonded nitrogen’s coming off and two of these nitrogens each have a double bond carbon and single bond carbon and the other two have both single bond carbon
Where EXACTLY does oxygen bind to haemoglobin ?
The Fe 2+ in the heme group.
Describe the relationship between O2 partial pressures and haemoglobin saturation.
Positive correlation
As partial pressure of oxygen increases the Hb saturation also increases
Describe the relationship between carbon dioxide partial pressure and haemoglobin affinity
Négative corrélation
As carbon dioxide partial pressure increases the affinity of Hb decreases
What two things mean oxygen is readily loaded onto Hb at the lungs?
Low carbon dioxide partial pressures (so doesn’t reduce affinity of Hb)
High oxygen partial pressures
Which way does the oxygen dissociation curve shift when carbon dioxide partial pressures Decrease
Left
Hb still has high affinity for oxygen
What two things mean oxygen is readily unloaded from Hb at te repairing tissues?
High carbon dioxide partial pressures (decreases affinity of Hb for oxygen)
Low oxygen partial pressures
Which way does the curve shift when carbon dioxide partial pressure increases ?
Right
Hb has lower affinity for oxygen so takes higher partial pressure for Hb to start becoming saturated
What are the normal axis for an oxygen dissociation curve?
Y axis - Hb affinity/saturation
X axis - oxygen partial pressure
What’s the difference between oxygen partial pressure and oxygen concentration of the X axis?
X
What happens if the carbon dioxide partial pressure is on the x axis?
X
How does low pH cause Hb to have a lower affinity for oxygen?
X
How does affinity of Hb for carbon monoxide work?
X
Explain what happens with Hb affinity at the lungs.
Carbon dioxide constantly removes so pH slightly raised (less H+ ions)
Higher pH alters shape of Hb so it loads oxygen more readily
Shape therefore increases Hb affinity for oxygen (also means it isn’t released whilst being transported through the blood to the tissues)
Explain what happens with Hb affinity at respiring cells
At respiring cells there is lots of carbon dioxide
Carbon dioxide dissolves to form carbonic acid which decreases pH of blood within tissues
Lower pH changes shape of Hb so it unloads oxygen more readily
Shape therefore decreases Hb affinity for oxygen and oxygen is unloaded into repairing cells
Explain the sequence of events to show how lots of oxygen is provided when cells respire a lot
Higher rate of respiration
More CO2
Lower pH
Greater Hb change in shape
Greater Hb affinity for oxygen decreases
More readily oxygen is unloaded
More oxygen available for respiration
How much oxygen is unloaded by Hb at tissues of low respiratory rates and what is Hb returning to the lungs like?
When it reaches a tissue with only a LOW RESPIRATORY RATE (so requires less oxygen) it unloads one oxygen molecule only.
The blood returning to the lungs still contains Hb which is quite saturated.
What is the normal saturation of Hb?
97% Hb loaded with oxygen at atmospheric pressures
What happens with Hb saturation when a repairing tissue is very active?
Requires more oxygen
Three oxygen molecules are unloaded per Hb (rather than just one)
Why do different species have different types of Hb?
Haemoglobin molecules with different affinities have evolved to adapt to different environments and conditions
Species living in an environment with lower oxygen partial pressures will have
Hb with a higher affinity for oxygen (than Hb of animals where oxygen partial pressure is higher)
How does a fétus receive oxygen?
From the mothers blood, oxygen dissociates from the mothers Hb and associated with fetal Hb in the placenta
What is fetal Hb affinity like?
High affinity for oxygen because fétus requires more oxygen for respiring cells as it grows
Fetal Hb curve
Shifts left
Hb has a higher affinity for oxygen
Benefit to fetal Hb having a higher affinity for oxygen?
At low partial pressures of oxygen in the placenta as much oxygen will dissociate from mother’s Hb and associate with fetal Hb
What ensures that a mother’s Hb dissociates enough oxygen so it can then be associated with fetal Hb?
X
Is there more CO2 ??
Why do adults not keep fetal Hb?
XXX
The high affinity for oxygen means less oxygen will be unloaded at respiring tissues
?? So how come this doesn’t affect babies???
Hb affinity of small organisms ?
Large SA:V
Lose lots of heat
Need to repaire to generate heat and maintain body temperature
LOWER AFFINITY
So oxygen unloads more readily at respiring cells
Hb affinity of active organisms ?
Cells depriving more so require more oxygen
Hb has a LOWER AFFINITY for oxygen
So oxygen more readily unloaded
Active organisms oxygen dissociation curve shift
Right
(Lower affinity for oxygen
What does the curve shifting left mean for unloading of oxygen ?
XXX
Oxygen unloaded only at lower partial pressures
Oxygen loaded more at ?
Affinity of Hb in organisms where there is low oxygen partial pressures
High affinity
Means even at low oxygen partial pressure Hb can readily associate with oxygen and load as much as possible in
Curve shift for affinity of Hb in organisms at low oxygen partial pressures
Curve shifts left
Classic example of an animal living at low oxygen partial pressures, what is their Hb affinity like?
Llama
Hb has high affinity for oxygen
Curve shifts left
Lugworm example
When tide goes out, less fresh water in lug worm burrow so lug needs to extract as much oxygen from the water that is left as possible
High affinity for oxygen
Curve shifts far to the left
What does an oxygen dissociation curve shifting really far to the left mean?
XXXX
Very high affinity of Hb for oxygen
Hb is fully (or very nearly) loaded with oxygen even when there is a tiny amount of oxygen in the environment
What does an oxygen dissociation curve shifting really far to the left mean?
XXXX
XX
Six situations oxygen dissociation curves shift left
1) Decreases in partial pressure of carbon dioxide
2) increase in alkalinity/pH
3) fetal Hb
4) living at high altitudes (low O2 pp)
5) living in anaerobic mud (low O2 pp)
6) CO poisoning
Why does oxygen dissociation curve shift left for CO poisoning?
XXX
X
Less oxygen able to bind to Hb because CO already there AO affinity increases so more oxygen can be bound ???
4 situations that oxygen dissociation curves shift right
1) increase in partial pressure of CO2
2) decrease in acidity/pH
3) strenuous exercise
4) hyperthermia
Why does oxygen dissociation curve shift RIGHT in hyperthermia ?
XXXXX ?
Right = lower Hb affinity for oxygen
Increased body temp
Needs to cool down body temp so less respiration that also produces heat?
Lower Hb affinity for oxygen
But then that would mean more oxygen unloaded at repairing cells so more respiration and heat which is what we do not want
Or does lower affinity for oxygen mean less oxygen loaded at lungs ??
???
Why does oxygen dissociation curve shift LEFT in hypothermia ?
XXX
Left = high Hb affinity for oxygen
Body temp needs to increase
So more respiration which also provides heat
So Hb to have higher affinity for oxygen so more
Affinity of oxygen is always associated with
What is being loaded
High affinity = readily loaded
Low affinity = readily unloaded
Unloading is oxygen always aaaociated with
Carbon dioxide partial pressures
High CO2 = readily unloaded
Low CO2 = NOT readily loaded (same as READILY LOADED)
When thinking what affinity suits the organisms
think about What affinity is best for LOADING of oxygen
Low affinity of Hb for oxygen means
Oxygen doesn’t readily load Hb at lungs ???
High affinity of Hb for oxygen means
Oxygen readily loads on to Hb at the lungs ??
Describe the arrow flow diagram of where blood flows through the heart
START: superior vena cava
Superior vena cava Right atrium (Tricuspid valve) Right ventricle (Semi lunar valve/pulmonary valve) Pulmonary artery LUNGS (Pulmonary vein) Left atrium (Bicuspid/mital valve) Left ventricle (Semi lunar valve/aortic valve) Aorta BODY
Bicuspid valve
Between left atrium and left ventricle
Also called mital valve
Left atrioventricular valve
Tricuspid valve
Between the right atrium and right ventricle
Also called aortic valve
Right atrioventricular valve
What are the atria and where do they receive blood from?
RECEIVE FROM VEINS
Right atrium - superior vena cava
Left atrium - pulmonary vein
Where do the ventricles pump blood to?
AWAY FROM HEART
Right ventricle - to the pulmonary artery
Left ventricle - to the aorta
What are vessels connecting the heart to the lungs called?
Pulmonary vessels
Where does the right ventricle pump blood to?
The lungs
Where does the left ventricle pump blood to?
The rest of the body
Why does the heart have two pumps and not just one?
Why is blood not pumped straight to the lungs to get oxygenated and then straight to the rest of the body from here?
At the lungs blood had to pass through tiny capillaries in the lungs in order to present a large surface area for gas exchange.
As it flows through capillaries there is a very large drop in blood pressure so the blood flow to the rest of the body would be very slow.
To increase blood pressure before it is distributed to the rest of the body the oxygenated blood from the lungs returns to the heart again (through the pulmonary vein) where it’s pressure increases and it is then pumped to the rest of the body through the aorta.
Why does the right ventricle have a thinner wall than the left ventricle?
It only pumps blood to the lungs whereas the left ventricle pumps it to the rest of the body (so has a muscular wall)
Why does the left ventricle have a thicker muscular wall?
Pumps blood to rest of body
So helps it to contract to create enough pressure to pump it.
Which side of the heart deals with which type (oxy or deoxy blood)?
Right side - deoxygenated blood pumped to lungs
Left side - oxygenated blood comes from lungs and is then pumped to the rest of the body
Aortopulmonary window
Hole connecting the aorta and the pulmonary artery
What do arteries usually carry
Oxygenated blood AWAY from heart
What do veins usually carry
Deoxygenated blood TOWARDS heart
Aorta
Connected to left ventricle
Carries oxygenated blood to all parts of body except lungs
Vena cava
Connected to right atrium
Carries deoxygenated blood from tissues to heart
Pulmonary artery
Carries deoxygenated blood (from right atrium) to the lungs
Unusual for artery it carries deoxygenated blood
Pulmonary vein
Connected to left atrium
Carries oxygenated blood form the lungs to then go to rest of body
Unusual for vein it carries oxygenated blood
How is the heart muscle supplied oxygen?
Coronary arteries branch off from the aorta shortly after it leaves the heart
Carries oxygen for heart muscle cells to respire
Blockage of coronary arteries can lead to
myocardial infarction
4 cardiovascular disease risk factors
Smoking
High blood pressure
Blood cholesterol
Diet
Smoking (CO)
1) CO binds irreversibly to the Hb in red blood cells reducing capacity of oxygen they can carry. Heart must work harder to supply the same amount of oxygen to tissue. Leads to raised blood pressure = increased risk of strokes + CHD.
Insufficient supply of oxygen to heart muscle during exercise = angina/myocardial infarction
Smoking (3)
Carbon monoxide
Nicotine
Decreases antioxidants
Smoking (nicotine)
Increases adrenaline production which increase heart rate raising blood pressure = increased risk of CHD and strokes
Nicotine makes platelets more sticky so higher risk of thrombosis and higher risk of strokes/heart attacks.
Smoking (antioxidants)
Antioxidants which are important for protecting cells from damage are decreased = cell damage in coronary artery wall more likely = atheroma formation
What can high blood pressure be caused by?
If genes cause high blood pressure then lifestyle won’t change this
Excessive prolonged stress, certain diets and lack of exercise
What happens if blood flows at high pressures in the arteries?
Heart must work harder to pump blood into arteries
Higher blood pressure in arteries means more likely to develop weakening of walls (aneurysm) and haemorrhage
To resist high blood pressures arterial walls may thicken, becoming harder and restricting blood flow.
How is cholesterol carried in the blood plasma?
Tiny spheres of lipoproteins
Heavy density lipoproteins
Remove cholesterol from tissues and transport it to the liver to be excreted
(Helped protect arteries from heart disease because they remove fats)
Low density lipoproteins
Transport cholesterol from the liver to the tissues
Bad cholesterol
How does high cholesterol level increase blood pressure?
High cholesterol levels mean more cholesterol is unloaded by low density lipoproteins (transport from liver to tissue) into the tissue in the arterial walls = arteries more restricted so higher blood pressures and risk of CHD + can lead to atheromas
Talk about diet and risk of heart disease
High levels of salt increase blood pressure
Foods that act as antioxidants (vitamin C and dietary fibre) reduce risk of heart disease
Heart (4 features)
- encapsulated by double layer of tough inelastic membranes called the pericardium
- pericardium fluid secreted between membranes to allow them to move over each other easily
- pericardium protects heart from over expansion caused by elastic recoil when it is beating very fast
- septum becomes rigid just before the heart contracts
What does the pericardium protect the heart from?
Over expansion caused by elastic recoil when the heart is beating very fast
What happens to the septum just before the heat contracts?
It becomes rigid
How many flaps does the bi and tri cuspid valves have ?
Bicuspid = two flaps
Tricuspid = three flaps
The cardiac muscle is …
Myogenic
contraction originates from within the muscle itself rather than from nervous impulses from the outside - neurogenic
Where are the tendinous chords attached and what do they do?
Tendinous chords attached to papillary muscles
Stop the valves from turning inside out
What do papillary muscles do to the tendinous chords?
Increase the tension of the tendinous chords so they can resist the powerful pressure of blood trying to flow backwards against tightly shut valves
What do valves do?
Maintain the one way flow of blood
Prevent back flow of blood when blood pressure in ventricles becomes higher than blood pressure in the atria
What is the ‘lub’ ‘dub’ sound you hear in a stethoscope produced by?
Valves closing = ‘lub’ sound
What do the vena cava do each heart beat ?
Construct so that blood doesn’t flow back into the veins
