Respiration 2 Flashcards
Dalton’s Law
each gas contribute to total pressue
Henry’s law
at a given temp, the amount of a particular gas is directly proportional to the partial pressure of the gas
fick’s law
diffusion of gas depends on the molecular weight and solubility of the gas, the surface area and the thickness of the membrane
total atmospheric pressure:
760 mmHg (Dalton)
Nitrogen accounts for:
78.6% or 597mmHg(Dalton)
Oxygen accounts for:
20.9% of air or 159mmHg(Dalton)
CO2 accounts for:
0.5% of air, or 3.8 mmHg(Dalton)
Each gas will dissolve in liquid in proportion to:
it’s partial pressure (Henry)
at equilibrium, the partial of the two phases (gas, liquid) will be:
equal
amount of each gas that will dissolve into liquid depends on:
solubility (CO2 is 20x more soluble in water than O2), little N2 will dissolve; and temperature (temp increases, solubility decreases) (henry’s law)
issues that effect gas diffusion at respiratory membrane:
The differences in partial pressure across the respiratory membrane are substantial. The distances involved in gas exchange are small. The gases are lipid soluble. The molecular weight of the gases is small. The total surface area is large. Blood flow and airflow are coordinated. (e.g. Blood flow is the greatest around alveoli with the highest PO2, where O2 uptake can proceed with maximum efficiency).
The differences in partial pressure across the respiratory membrane:
substantial
The distances involved in gas exchange are
small
the gases are:
lipid soluble
molecular weight of the gases is:
small
total surface area of gases is:
large
bloodflow and air flow are coordinated becasue:
blood flow is greatest around alveoli where the PO2 is the highest
alveolar gas carries _____ CO2 than atmospheric air:
much more
atmospheric gas PO2/Alveolar gas
159/100
atmospheric gas PCO2/Alveolar gas
3.8/40
before pulmonary capillaries exchange gas, the ratio of O2/CO2 is;
40/45
After the pulmonary capillaries exchange gas, the ratio of O2/CO2 is:
100/40 (same as in the Alveolus)
CO2 is _____ times more soluble in the plasma and alveoli fuild than O2
20x
ratio of O2/CO2 in systemic capillaries before exchange with the tissue
O2=95, CO2=40.
ratio of O2/CO2 in systemic capillaries after exchange with the tissue
O2=40,CO2=45
levels of PO2 at atmospher, alveolar, tissue:
159,100,40
Level of PCO2 at atmospher, alveolar, and tissue:
3.8, 40,45
•O2 is carried in blood in two ways:
o1. 5% is dissolved in plasma
o98. 5% is bound to each Fe of hemoglobin (Hb) in RBCs
Each Hb molecule is composed of four:
polypeptide chains (2a and 2b subunits), each with an iron-containing heme group
Oxy-hemoglobin:
hemoglobin-O2 combination
Deoxy-hemoglobin:
ohemoglobin that has released O2
Loading (association) and unloading (dissociation) of O2 is facilitated by :
a change in the shape of Hb
•Percent of ________ can be plotted against _________
•Percent of Hb saturation can be plotted against PO2 concentration.
- Fully saturated (98-100%):
- Partially saturated:
- Fully saturated (98-100%): all four heme groups carry O2
- Partially saturated: when only one to three heme groups carry O2
Effect of pH. When the pH drops below normal levels,
Bond between O2 and Heme weakens, more oxygen is
released; the oxygen–hemoglobin saturation curve shifts to the
right. When the pH increases, less oxygen is released;
the curve shifts to the left. Bohr effect
P 50 is the partial pressure of O 2 at which hemoglobin is 50% saturated (2/4 heme molecules are bound by O2).
An increase in P 50 reflects a _____ in affinity, and a decrease in P 50 reflects an ______in affinity.
decrease/increase
Effect of temperature. When the temperature
rises, _____ oxygen is released; the
oxygen–hemoglobin saturation curve shifts to the
______. Bohr effect
more/right
•The structure of fetal hemoglobin (Hb F)
oDiffers from that of adult Hb
oHas two __ chains instead of two b chains
oAfter birth, the ____ rapidly destroys fetal erythrocytes carrying hemoglobin F
oThe baby’s erythroblasts begin producing Hb A.
g/liver
•At the same PO2:
oFetal Hb binds _____ O2 than adult Hb binds O2, which allows fetus to associate O2 from maternal blood
more
•Other factors such as:
oTemperature
oBlood pH
Metabolic activity within RBC, 2, 3-diphosphoglyceric acid (2,3-DPG), a byproduct of glycolysis in RBC. It binds to ____ chain of _____and _____their affinity for O2, causing O2-Hb saturation curve to shift to the right
b/deoxyhemoglobin/reduces
mnemonic for low oxygen scenarios:
man from OH with woman from hip anne from CT
“Hyp An Is His”
- CO has much __affinity to heme than O2
- Competitive binding causes ___binding sites for O2.
higher/decreased
when p50 of oxygen goes down, affinity goes:
up
CO2 is Converted to a molecule of ____ via ______
carbonic acid/carbonic anhydrase (70%)
CO2 Binds to the ______ of hemoglobin molecules within red blood cells (23%).
NH2- portion (amino group)
______ percent CO2 is dissolved in plasma
•Dissolved in plasma (7%).
Carbon Dioxide Transport
(by carbonic anhydrase):
•Occurs primarily in RBCs, where enzyme carbonic anhydrase reversibly and rapidly catalyzes this reaction.
•In systemic capillaries, after HCO3– is created, it quickly diffuses from ___ into _____(ICF to ECF)
RBCs/plasma
oOutrush of HCO3– from____ is balanced as ____ moves into RBCs from ____(counter-transportation, passive)
oOutrush of HCO3– from RBCs is balanced as Cl– moves into RBCs from plasma (counter-transportation, passive)
•Referred to as chloride shift
•In pulmonary capillaries, the processes occur in reverse
oHCO3– moves ____ RBCs while Cl- moves ____ RBCs back into plasma
•In pulmonary capillaries, the processes occur in reverse
oHCO3– moves into RBCs while Cl- moves out of RBCs back into plasma
oHCO3– binds with ____ to form _____
HCO3– binds with H+ to form H2CO3
H2CO3 is split by ______ into _______ and then dissolves ____ the alveoli
H2CO3 is split by carbonic anhydrase into CO2 and water
oCO2 diffuses into alveoli
•Changes in respiratory rate and depth affect blood pH
Slow, shallow breathing causes an ______ in CO2 in blood, resulting in a _____in pH
oSlow, shallow breathing causes an increase in CO2 in blood, resulting in a drop in pH
Rapid, deep breathing causes a ______ in C O2 in blood, resulting in a ____in pH
Rapid, deep breathing causes a decrease in C O2 in blood, resulting in a rise in pH
•Carbonic acid–bicarbonate buffer system: helps blood resist changes in pH caused by metabolism.
oIf H+ concentration in blood rises, excess H+ is removed by combining with _____ to form H2CO3, which dissociates into _____ and _____, to be breathed out.
HCO3-/CO2,H2O
If H+ concentration begins to _____, _______ dissociates, releasing H+
drop/H2CO3 dissasociates
_____ is considered the alkaline reserve of carbonic acid-bicarbonate buffer system
It only works when the respiratory system is functioning normally.
•E.g. If the acidosis is caused by respiratory issue, this carbonic acid-bicarbonate buffer system will not play a role in compensating blood pH.
HCO3-
2 Gas transportory systems for O2:
Hb Heme, Dissolved in plasma
3 Gas transportory systems for CO2:
RBC (carbonic acid), Hb NH2-terminal, dissolved in plasma
•Lung perfusion: blood flow to the alveoli.
Alveolar capillaries ______when the local PO2 is low. Blood flow is re-directed to high PO2 area (because blood comes to lung to pick up O2).
Alveolar capillaries constrict when the local PO2 is low. Blood flow is re-directed to high PO2 area (because blood comes to lung to pick up O2).
•Alveolar ventilation: airflow.
Bronchioles _______ in diameter when CO2 goes up (because the purpose of the conducting zone is to direct CO2 generated by the tissue out of the airway)
Bronchioles increase in diameter when CO2 goes up (because the purpose of the conducting zone is to direct CO2 generated by the tissue out of the airway)
Alveolar ventilation: airflow.
Bronchioles _______ in diameter when CO2 goes up (because the purpose of the conducting zone is to direct CO2 generated by the tissue out of the airway)
Bronchioles increase in diameter when CO2 goes up (because the purpose of the conducting zone is to direct CO2 generated by the tissue out of the airway)
Opposite mechanism seen in systemic arterioles that _____ when oxygen is low and ______ when high
•Opposite mechanism seen in systemic arterioles that dilate when oxygen is low and constrict when high
•Perfusion
o______ reaching alveoli
•Ventilation
oAmount of _______ reaching alveoli
•Perfusion
oBlood flow reaching alveoli
•Ventilation
oAmount of gas reaching alveoli
- Ventilation and perfusion rates must be matched for optimal, efficient gas exchange
- Both are controlled by local auto-regulatory mechanisms
•Changing _______ of local arterioles and bronchioles synchronizes ventilation-perfusion
diameters
Ventilation-perfusion is never balanced for all alveoli because:
- Regional variations may be present, due to effect of gravity on blood and air flow
- Occasionally, alveolar ducts plugged with mucus cause unventilated areas
•Chemical Factors Influencing
Breathing Rate and Depth
PCO2:
oMajor stimulus for respiration
oHypoventilation
oHyperventilation
Chemical Factors Influencing
Breathing Rate and Depth: PO2
oNot a major one until PO2 drops to 60 mm Hg
Chemoreceptor Response to Increase in PCO2:
- Increased arterial PCO2 →
- Increased PCO2 in CSF and
- stimulation of peripheral arterial (aortic body and carotid body) and central chemo-receptors (CO2 is permeable to blood brain barrier) in brain stem →
- Increased respiratory rate →
- Increased elimination of CO2 at alveoli →
- Decreased arterial PCO2 →
- Restored homeostasis
Hyperventilation:
- An increase in the rate and depth of breathing that exceeds the body’s need to remove CO2.
- Low CO2 in the blood causes cerebral vasoconstriction, reduces brain perfusion and produces cerebral ischemia.
- A swimmer hyperventilates voluntarily before jumping in the pool so that they can hold their breath longer during swim meet. Is it safe?
Voluntary Hyperventilation
- PO2 rarely drops below 60 mm Hg during regular breath holding because decreasing PO2 (inspiration)usually indicates CO2 accumulation (expiration) under physiological conditions.
- The rising of PCO2 is enough to make breathing unavoidable (chemo-receptor).
- Strenuous hyperventilation can lower PCO2 so much that a lag period occurs before it rebounds enough to stimulate respiration again.
- This lag may allow PO2 to fall well below 50 mm Hg, which causes the swimmer to black out.
Arterial pH:
•Changes in arterial pH can modify respiratory rate and rhythm even when CO2 and O2 levels are normal.
oE.g. Metabolic acidosis
•Elevated H+ stimulates peripheral, but not central, chemo-receptors, because H+ is not permeable to the blood brain barrier, but CO2 is.
Pulmonary Circuit:
- Pulmonary circuit is low-pressure, but high-volume circulation.
- All the blood passes through the lungs about once each minute.
- Lung capillary endothelium is an ideal location for enzymes act on materials in the blood.
