Respiration 2 Flashcards
State Daltons Law
Total pressure = sum of partial pressures
P= pN2 +pO2+pCO2+pH20
What is the partial pressure of a gas?
Pressure the gas would exert if it was the only gas present
What is the make up of the air?
Nitrogen 78%
Oxygen 21%
What is the relationship between Alveolar ventilation and alveolar pp of O2?
As ventilation increases the pp of O2 increases
curve upwards and level off
What is the relationship between Alveolar ventilation and alveolar pp of CO2?
As ventilation increases , pp of CO2 decreases (sharp downwards curve then level off)
State Fixs Law
Diffusion coefficent= K solubility (x) / square root of Mwt(x)
t= respiratory membrane
A= area for diffusion
P=chnages in pp
What is the rate limiting step in the movement of gases into solution ?
The rate at which the gases dissolve into the tissue water
What are 5 parts of the respiratory membrane?
Alveolar epithelium
Epithelial basement membrane
Capillary basement membrane
Capillary ENdothelium
What is the average diameter of the pulmonary capillaries
~ 5 mm
What is the distance between the alveolar space and capillary lumen?
1-2um and this is covered in about 1ms by O2
Which has higher pp in O2 and CO2?
Pulmonary Arterioles or Pulmonary venules
O2= Pulmonary Ventricles Co2= Pulmonary Arterioles
How long does it take for blood to equilibrate with alveolar gases in the normal lung?
<0.2 sec
What is perfusion?
Blood flow
During exercise the blood flow increases, why is this advantageous?
Time in capillary reduces so increased movement of CO2 and O2
Also increased pulmonary arterial pressure which causes closed vessels to open and vessels to dialate
What are the 2 physiological regulated factors determined O2/Co2 transfers between alveolus and tissue?
rate of alveolar ventilation
Blood flow
In the higher part of the lung which is higher
rate of alveolar ventilation or blood flow
rate of alveolar ventilation
In the lower part of the lung which is higher
rate of alveolar ventilation or blood flow
Blood flow
State the equation used to find alveolar ventilation
V= (V Tidal-V dead) x resp.rate
What is the ans to rate of alveolar ventilation/ Blood flow
about 0.8
What is hypoxic vasoconstriction?
When PO2 within the alveoli decreases there is a decrease in blood flow to the alveolus
What is the result of hypoxic vasoconstriction?
O2-sensitive K+ channels in the smooth muscle membrane of the pulmonary arterioles. At low O2 the K+ channels close, the cell depolarizes and contracts, so these arterioles partially close.
Why is hypoxic vasoconstriction important?
Important in the pulmonary circulation helping to match perfusion with ventilation
What happens when there is a blockage of one alveolar region?
Decreased tissue PCo2 around an underventilated alveoli constricts their atriers diverting blood to better ventilated alveoli
Define Anatomical DS
The volume of respiratory tract involved in conducting gas not in transfer to blood
Define Physiological Dead Space
The portion of the tidal volume not participating in gas exchange with pulmonary capillary blood
What is the equation for physiological DS
Physiological DS = Anatomical DS + Alveolar DS
State Henrys Law
Con of dissolved gas= pp x solubility coefficient
Is o2 easily soluble in H2o?
NO
1g of Hb carries how much O2 when saturated?
1.3mls
What is the concentration of HB?
150g
What is the equation of HB reacting with O2?
Hb+4O2 Hb(O2)4
State the equation of oxidation of HB?
is it easily reduced?
Hb (Fe2+) hB(Fe3+)
hard to reduce
What is used as an antioxidant for cyanide and why?
Amyl Nitrate
Acts as an oxidant to induce formation of methemoglobin
At what mm of Hg is fully saturated?
80mm
What type of binding does O2 have with Hb?
Allosteric activation
Describe the structure of Hb
Tetramer
Heme
Porphyrin ring
Formed of 4 Pyrol groups
Why is the S shaped curve advantageous?
High affinity only- cant release much O2 to tissue
Low affinity- cant pick up much O2 at the lungs
2,3-Bisphosphate also alters position of the O2/Hb curve-how?
Strongly –ive charged binds to haemoglobin and reduces O2 allosteric retention
(stabilises the tense low affinty form)
–in lungs, slight reduction in saturation but in tissues results in much greater O2 release
name 4 things that change Hb affinity for O2
[H+]
pp of Co2
Temp
[2,3-DPG]
(also kinda CO)
Describe the Haldane effect
central peptide of oxyhaemoglobin (lung) is a stronger acid than haemoglobin (tissue).
In Lung
(1) H+ ions react at carbamino N termini(-NH3+) of Hb displacing CO2
(2) Increased acidity (H+ ) also causes bicarbonate ions to form carbonic acid; this then dissociates into water and carbon dioxide(help of C anhydrase), which is released into the alveoli.
Hence in the lungs-oxyhaemoglobin causes increased CO2 is loss from blood
Opposite occurs in the tissue- deoxygenated blood carries more CO2
How is CO2 transported?
As bicarbonate ion w/ blood proteins and solution in plasma
How is CO2 transported in the tissue?
IN tissue capillaries, carbon dioxide combines with water inside RBCs to form carbonic acid (C Anhydrase) which dissociates to form bicarbonate ions and hydrogen ions, bicarbonate ions leave the RBC and chloride ions enter so separating the reactants
How is CO2 transported in the lungs?
IN lung oxyhaemoglobin forms and is a stronger acid, binds less readily with carbon dioxide and releases protons which reverse bicarbonate reaction - (Haldane effect), together causes a release of CO2 in lungs
What is respiratory acidosis?
Lowered plasma pH indirectly causes an increase in respiration rate to drive off CO2
