lecture 6 control of respiration Flashcards
How do chemo receptors control respiration?
via a feedback loop
What triggers chemo receptors and what do they do when they are triggered?
they are triggered by arterial CO2, H20 and pH, the chemoreceptors pick up changes in the acidity of blood. the respiratory centres react to the signals and changes picked up by the chemoreceptors, the respiratory centres then trigger respiratory muscles which results in the effect of ventilation
Chemoreceptors->respiratory centres->respiratory muscles->ventilation
What is lung perfusion?
blood supply to the lungs from pulmonary and systemic circulation
How are the lungs supplied with blood?
via pulminary and systemic circulation
What does the efficiency of gas exchange depend on?
large surface area of the capillaries
What are traits of the alveoli that affect gas exchange?
low resistance (thin alveolar walls) and the effects of gravity
Where does more perfusion take place and what is that affected by?
base of lungs bc of gravity
What is the space around the alveoli is made up of? Why is this important?
80-90% of the space around alveoli is ade up of blood vessels there are a network of capillaries that surround alveoli
What path does the blood take from the right side of the heart to the rest of the body?
deoxyginated blood that has lost oxygen to cellular respiration travels up through systemic circulation and then pulmonary circulation where it then travels through the lungs and exchanges co2 with o2 at alveoli
What is ACE?
endothelial cells of alveolar capillaries release
What is each lobule of the lung supplied by?
an arteriole and venule supply the lung lobules
What does the amount of oxygen bound to the Hb depend on?
plasma O2 and the amount of haemoglobin
-plasma o2 determines % saturation of Hb
amount of haemoglobin determines the total number of haemoglobin binding sites
Hb binding sites is calculated from the Hb content per RBC x number of RBCs
amount of oxygen bound to Hb is calculated by % saturation of Hb x total number of Hb binding sites
What is the structure of the red blood cell and haem?
red blood cell is made up of haemoglobin and haemoglobin is made up of 4 haem units
How does oxygen uptake occur from the alveoli to the red blood cells?
gases are carried through blood and control of gas exchange happens via the lungs and cardiovascular system.
haemoglobin binds to 98% of haemoglobin to form oxyhaemoglobin HbO2
uses co-operative binding- one molecule binding makes it easier for others to bind bc structutre is changed
What is the drop in partial pressure that occurs when the RBC enters a tissue?
caused by oxygen being released from red blood cells and them entering the tissues due to the demands of cells’ metablic demands
What does the amount of oxygen binding to haemoglobin depend on?
Po2, iron core, 4 haem groups which can each bind to one 02 molecule
What affects our breathing rate?
amount of CO2 we have in our body- their partial pressures
What is haematology concerned with?
study of blood and blood disorders
How is CO2 distributed?
it is dissolved at the lungs and during cell metablism which allows it to be transported via red blood cells through veins
7% is dissolved in plasma
23% is transported as Hb-CO2
70% as HCO3-
how is Co2 carried and transported
from the tissues to the lungs
-diffuses from cell to blood across the alveolar membrane due to pressure grandient
24x more soluble than O2 and Co2 has no carrier to transfer it
Where is Co2 carried?
to the lungs
How does co2 go from cell to blood? why?
Diffusion from Cells: CO2 produced within cells diffuses across cell membranes, moving from areas of higher concentration inside the cells to areas of lower concentration outside the cells. This diffusion occurs down the concentration gradient, driven by the higher concentration of CO2 inside the cells due to its production during cellular metabolism.
Transport in Plasma: Once CO2 diffuses out of cells, it dissolves in the plasma
Is Co2 more soluble than O2? Does CO2 need a carrier?
it is 24x more soluble and does not need a carrier
How efficient is Hb at binding with O2 and what does it form?
it binds to 98% of O2 and forms Hb02 (oxyhaemoglobin)
What traits does Hb have that allows it to efficiently bind with O2?
an iron core, 4 haem groups
cooperative binding which increases carrying capacity by 70%
What is Haemoglobin made up of?
an iron core and 4 haem groups
What are the percentage breakdowns of O2 and CO2 transport?
Oxygen:
98.5% as hb-02
1.5% dissolved in plasma
C02:
7% dissolved in plasma
23% as Hb-02
70% as HCO3-
Explain the traits of an oxygen dissociation curve, Why is the curve sigmoidal?
partial pressure of oxygenated blood in systemic arteries is 100%
deoxygenated blood-
20mmHg P02 required for contracting skeletal muscle and saturation of 25%
partial pressure of deoxygenated blood in systemic veins at rest is 40mmHg at 75% saturation
What are the benefits of the sigmoidal curve?
amount of O2 in blood is not affected by small fluctuations in P02 (can be between 100 -60mmHg)
at Po2 of the tissues the curve is very steep meaning there is a larger pressure on the gas exchange to release CO2 from tissues into the blood
Under normal circumstances what is the temperature, pH and Pco2?
45mmHg
7.35-7.45 pH
37 degrees celcius
At rest what is the percentage saturation of deoxygenated blood in the skeletal muscle and systemic veins and systemic arteries?
skeletal muscles- 35%
systemic veins- 75%
oxygenated blood in systemic arteries is 95%
What is the BOHR effect?
the shift in the haemoglobin saturation curve caused by a pH change
What is chronic hypoxia?
an extended period of low oxygen and low oxygen pH
What happens when H+ ions bind to haemoglobin?
they reversibly change shape of the haemoglobin molecule and their grip on O2 molecules becomes weaker
What does decreasing Ph (increasing h+ions) cause?
it causes decrease in O2 saturation which results in a shift to the right on a dissosociation curve
increasing pH leads to curve shifting to the left
What is a major cause of the bohr effect?
drop in pH
What does CO2 increase the production of?
H+ ions
What is a respiratory quotient?
the relationship between the amount of carbon dioxide produced and oxygen absorbed (VA/Q)
What does steady-state alveolar ventilation equal?
PCO2
What does the infinity sign and the 0 indicate?
infinity sign= ventilation and no perfusions
0= perfusions and no ventilation
What are the actual values of the respiratory quotient usually?
0.7-1
What can affect our respiratory quotient?
(DPG) metabolite of carbohydrate metabolism in RBCs
the metabolites can act as an inhibitor which binds to haemoglobin structure
What is DPG?
a metabolite produced via carbohydrate metabolism in RBCs
What does DPG do?
can inhibit oxygen from binding to Hb, it can cause a shift to the right (decreasing saturation) and this can occur during exercise, a drop in blood pH, increase in thyroid hormones and growth hormones
What does an increase in DPG do? How does it affect the curve and under what conditions?
can inhibit oxygen from binding to Hb, it can cause a shift to the right of a dissosociation curve (decreasing saturation) and this can occur during exercise, a drop in blood pH, increase in thyroid hormones and growth hormones
Why does foetal haemoglobin have greater O2 affinity than the mother?
because faetal haemoglobin has poor binding of 2,3 DPG
Why can carbohydrate metabolism be a problem in red blood cells? How can this affect our saturation of haemoglobin?
because it can produce metabolites such as DPG, which can act as inhibitors that bind to haemoglobin strucure
What happens to carbon dioxide when it is being transported in the blood?
- Co2 diffucses out cells and into systemic capillaries
- only 7% of co2 remains dissolved in plasma
- nearly a quarter of the co2 binds to haemoglobin, forming carbaminohaemoglobin
- 70% of the co2 load is converted to bicarbonate and H+ ions, haemoglobin buffers the H+ ions
- HCO3- enters plasma in exchnage for CL- (the chloride shift)
- at the lungs dissolved CO2 diffusses out of the plasma
- via the law of mass action, co2 unbinds from haemoglobin and diffuses out of the RBC
- the carbonic acid reaction reverses which pulls HCO3- back into the RBC and converts it back to CO2
How does surfactant decrease the surface tension of the alveoli?
surfactant decreases the surface tension of the alveoli by disrupting hydrogen bonds between water molecules at the air-fluid interface.
