D.6-Transport of respiratory gases Flashcards
The degree to which Haemoglobin binds to O2 is determined by what?
Partial Pressure of O2 (PO2) in the blood
What is the PO2 in air?
160 mm of mg
What is the PO2 in the lungs?
40 mm of mg
Haemoglobin has high affinity for?
O2
Haemoglobin likes dropping off passengers (dissociation of O2) when?
There are LOTS of passengers
What happens to the dissociation of Haemoglobin once it is getting to its last passenger?
It doesn’t want to drop it off
→ it holds on to it until the end!
% of O2 carried in blood:
1) Bound in Haemoglobin
2) Dissolved in blood plasma
1) Bound to Haemoglobin = 98.2% of all O2 in blood
2) Dissolved in blood plasma = 1.5%
What are the 3 forms and the percentage of CO2 that is carried in blood?
1) Dissolved as CO2 = 7%
2) Reversibly converted to bicarbonate (hydrogen carbonate ions = HCO3 -) that are dissolved in bl. plasma = 70%
3) Bound to plasma proteins = 23%
At what pH does blood need to be kept between?
7.35-7.45
What does the binding of Haemoglobin to CO2 makes?
Carbaminohaemoglobin
Haemoglobin also binds to H+ to make what?
Haemoglobonic acid
What is the Chloride shift?
+ When the cell is negatively charged because of the formation of the Hydrogen carbonate ions
= don’t want the positive ions to rush in so RBC cell:
→ pumps Cl- ions INto it’s cell
→ forces the HCO3- OUT of the RBC through a protein channel
Hydrogen carbonate ion is a buffer, so it doesn’t like change
Chemo-receptors in which area of the body can detect change in blood CO2? (3)
1) Medulla
2) Aorta
3) Carotid artery (supplying blood to the brain)
Why does high level of CO2 in blood trigger an increase in ventilation rate?
In order to rid the body of CO2 buildup
→ CO2 diffuses into the alveoli and ventilation expels the CO2 from the body
What regulates the rate of ventilation?
The respiratory control centre in the Medulla oblongata
What are the 2 sets of nerves that travel from to the lungs from the respiratory centre?
1) Intercostal nerves = stimulate the intercostal muscle and thorax
2) Phrenic nerves = stimulate the diaphragm
When the lungs expand due to the stimulation from the nerves = what happens?
+ Stretch receptors in the walls of the chest and lungs = sends signals to the respiratory centre = triggers an end of the signals
→ leading to inspiration until the animal exhales
+ Then a new signal is sent
In the Kidney the H+ ions can be secreted into the urine bound to what and what does it lead to?
Bound to buffers. To raise the pH
→ leads to greater amt of bicarbonate to be reabsorbed from the tubules to neutralise the acid
If the blood becomes too basic = what happens?
Bicarbonate ions can be secreted into the distal convoluted tubules of the Kidney
Chemical buffers = exist within the extracellular fluid = these can’t remove the acids or bases BUT what can they do?
Can minimise the effect
At high altitude there’s low pO2 in the air what happens as a consequence?
Haemoglobin may not become fully saturated → tissue may not be adequately supplied w/ O2
What physiological changes happen at high altitudes? (3)
+ RBC production increases
→ increases total vol. of circulating haemoglobin
+ Ventilation rate increases to increases gas exchange
+ Muscles produce more Myoglobin to ensure delivery of oxygen to the tissues
Populations living permanently in higher altitudes have greater what?
+ Mean lung surface area
+ Larger vital capacity
Than ppl living at sea level
→ O2 dissociation curve shifts to the RHS
Emphysema patients have a “barrel chest”, what does that mean?
Large areas of trapped air in the lungs
→ leading to the lungs being in ‘inspiration’ position in the ventilation cycle
What is the main cause of Emphysema?
Long-term exposure to airborne irritants
Most common airborne irritants (4)
+ Tobacco smoke
+ Air pollution
+ Coal
+ Silica
3 factors that causes the damage to the lungs
1) Oxidation reactions by high conc. of chemicals = free radicals in tobacco smoke
2) Inflammation due to body responding to irritating particulates within smoke
3) Free radicals and other components of tobacco smoke impair the activity of enzyme A1AT = normally block activity of elastase.
Rare genetic diseases that causes Emphysema?
Deficiency in the enzyme A1AT (alpha-1-antitrypsin)
