Physiology Flashcards
(21 cards)
Where are RBCs broken down
liver, spleen, bone marrow
What is more soluble - CO2 or O2?
CO2 is 20x more soluble than oxygen in both blood and alveolar fluids. As a result, the relative concentrations of oxygen and carbon dioxide that diffuse across the respiratory membrane are similar
At the respiratory membrane in the lungs what is the pressure gradient of
- oxygen
- carbon dioxide
Oxygen: ~64mmHg - 104mmHg alveolar pO2, 40mmHg blood pO2
Carbon dioxide: ~4mmHg - 40mmHg alveolar pCO2, 45mmHg blood pCO2
however as CO2 is 20x more soluble, the relative concentrations of CO2 and O2 that diffuse acorrs the respiratory membrane are similar
What does erythropoetin (EPO) do and where is it made?
made by the kidneys
stimulates erythropoesis
- hence renal impairment can cause anaemia
Where is 2,3 Bisphosphateglycerate (2,3-BPG) found and what does it do?
In RBCs
It binds oxyhaemoglobin that has already lost some oxygen with high affinity, decreases Hb affinity for oxygen, promoting release of remaining oxygen and stabilising the tense form of Hb.
V/Q ratio is the volume of air through the lungs/min divided by the volume of blood through the lungs per min.
As there are differences in ventilation and perfusion in different areas of the lung, the average V/Q ratio for a human is what?
0.8
What happens to both ventilation and perfusion as you move from the apex to the base of the lungs, what is the difference in this, and what does this mean for the V/Q ratio?
both ventilation and perfusion increase but perfusion increases at a faster rate (V/Q) so the V/Q ratio decreases
In a normal, healthy individual how does the body respond to a change in either ventilation or perfusion?
In a normal, healthy individual, changes in either ventilation or perfusion will result in correction of the other factor to ensure an appropriate V/Q ratio
ventilation problem - increased perfusion
perfusion problem - increased ventilation
Lifespan of an RBC?
~120 days
How many oxygen molecules can Hb carry?
4 - one per haem group
What is positive cooperativity?
The more oxygen molecules bound to Hb the higher Hbs affinity for oxygen
Which factors shift an oxygen dissociation curve to the right?
'CADET go RIGHT' A rise in any of the following: CO2 Acidity DPG Exercise Temperature
What is the difference between fetal and adult Hb?
Fetal Hb has a higher affinity for oxygen than adult Hb so the fetus can successfully compete with its mother for oxygen whilst in the womb
Type I alveolar cell function
Gas exchange
Type II alveolar cell function
Type II alveolar cells produce surfactant. This reduces alveolar surface tension throughout the lungs, which improves pulmonary compliance and prevents alveoli from collapsing during expiration.
The diaphragm is an important mechanism in voluntary respiration. Damage of the nerve supply to the diaphragm can impair voluntary breathing. Which is the correct description of the motor nerve supply to the diaphragm?
The diaphragm is supplied by C3, C4 and C5 via the phrenic nerves. A useful mnemonic to remember is ‘C3-4-5 keeps the diaphragm alive’.
Which mode of transport accounts for 80% of CO2 transport in the blood?
As H+ and HCO3-
What are the 2 more minor methods of CO2 transport in the blood?
Dissolved in plasma (5%) As carbaminohaemoglobin (bound to Hb) (10%)
Under what conditions does the body produce 2,3 diphosphoglycerate (2,3-DPG)?
in response to hypoxia - for example in anaemia and high altitude
-reduced Hb affinity for oxygen so it is unloaded to tissues more easily
Is perfusion higher at the base or the apex or the lungs and why?
Perfusion is higher at the base of the lungs, lower at the apex as the force of GRAVITY is higher
Is ventilation higher at the base or the apex or the lungs and why?
Ventilation is higher at the base of the lungs as the alveoli are smaller there due to higher intrapleural pressure so they can expand more
