The Heart Flashcards
What are the adaptations of erythrocytes (rbc)
-biconcave shape, larger SA than simple disc structure or sphere, more SA for gas diffusion. Also helps them pass through narrow capillaries.
-In adults, erythrocytes are formed continuously in the red bone marrow. Mature erythrocytes lose their nucleus, maximises haemoglobin that fits into cells. Also limits their life-last about 120 days in bloodstream.
What is haemoglobin
Red pigment that carries oxygen and gives colour. Very large globular conjugated protein made up of four peptide chains, each with an iron-containing haem prosthetic group. 300 million haemoglobin molecules in each rbc.
How does haemoglobin carry oxygen
Steep conc. gradient between rbc and alveoli. Oxygen moves into erythrocytes and binds with haemoglobin.
What is positive cooperativity
- As soon as one oxygen molecule binds to haem group, the molecule changes shape, making it easier for the next molecule to bind.
-Because the oxygen is bound to the haemoglobin, the free oxygen concentration in the erythrocyte stays low, so a steep diffusion gradient is maintained until all the haemoglobin is saturated with oxygen.
What happens when the blood reaches the body tissue
Situation is reversed. Conc. of oxygen in cytoplasm of body cells is lower than in the erythrocytes. Oxygen moves out. Once the first oxygen molecule is released by the haemoglobin, the molecule again changes shape and it become easier to remove the remaining oxygen molecules.
Describe stages of the oxygen dissociation curve
- At low p02, few haem groups are bound to oxygen, so haemoglobin doesn’t carry much oxygen.
- At higher p02, more haem groups are bound to oxygen making it easier for more oxygen to be picked up.
- The haemoglobin becomes very saturated at very high p02 as all the haem groups become bound.
What happens to the erythrocytes when you are not very active
Only 25% of oxygen carried is released into body cells. The rest acts as a reservoir for when body demands more.
What’s the effect of carbon dioxide on oxygen Bohr effect.
As partial pressure of C02 increases, haemoglobin gives oxygen more easily.-
Why is the Bohr effect important
-Active tissues- high partial pressure of C02, haemoglobin gives up its oxygen more readily.
-In the lungs where the proportion of C02 is low, oxygen binds to the haemoglobin molecules easily.
What is feral haemoglobin
Has a higher affinity for oxygen. Oxygenated blood from mother runs close to deoxygenated fetal blood in placenta.
What are the three ways carbon dioxide is transported to the lungs
-5% carried dissolved in plasma
-10-20% is combined with amino groups in the polypeptide chains of haemoglobin to form a compound called carbaminohaemoglobin.
-75-85% is converted into hydrogen carbonate ions in the cytoplasm of the rbc.
How does carbon dioxide form carbonic acid
Carbon dioxide reacts slowly with water to form carbonic acid. The carbonic acid then dissociates to form hydrogen ions and hydrogen carbonate ions.
Why are carbonate ions formed quickly in rbc cytoplasm
The cytoplasm contains high levels of the enzyme carbonic anhydrase- catalyses reaction between carbon dioxide and water.
What is the chloride shift
Negatively charged hydrogen carbonate ions move out of the erythrocytes into the plasma by diffusion and negatively charged chloride ions move into the erythrocytes, which maintains the electrical balance of the cell.
Why does the chloride shift happen
By removing C02 and converting it to hydrogen carbonate ions, the erythrocytes maintain a steep concentration gradient for carbon dioxide to diffuse from the respiring tissues into the erythrocytes.
What happens when the blood reaches the lung tissue
Carbonic anhydrase catalyses the reverse reaction, breaking down carbonic acid into carbon dioxide and water. Hydrogen carbonate ions diffuse back into the erythrocytes and react with hydrogen ions to form more carbonic acid. Chloride ions diffuse out of rbc into plasma.
How does haemoglobin play a role in the chloride shift
Acts as a buffer and prevents changes in the pH by accepting free hydrogen ions in a reversible reaction to form haemoglobinic acid.
What is the heart made out of
Cardiac muscle- contracts and relaxes in regular rhythm. Doesn’t get fatigued. Coronary arteries supply cardiac muscle with oxygenated blood it needs to keep contracting and relaxing.
What are the atrioventricular valves called
Right-tricuspid valve
Left-bicuspid valve
What do the tendinitis cords in the heart do
Make sure the valves are not turned inside out by the pressures exerted when the ventricle contracts.
What’s the inner dividing wall of the heart called
The septum-prevents mixing of blood
What’s diastole
Heart relaxes, atria and ventricles fill with blood. The volume and pressure of the blood in the heart fills, but pressure in arteries is at minimum.
What’s systole
Atria contract, then ventricle. Pressure increases dramatically. Volume and pressure low at end, though high in arteries.
Where do heart sounds come from
Made by blood pressure closing the heart valves. Two sounds- atrioventricular valves closing and ventricle contract, then semilunar valve closing as ventricle relax.
