Pulmonary Physiology (3) Flashcards
what is internal respiration? (2)
- systemic gas exchange
- exchange of O2 and CO2 between systemic capillaries and tissue cells
describe the PO2 of blood pumped into systemic capillaries versus PO2 in tissue cells during internal respiration
PO2 of blood pumped into systemic capillaries is higher (100mmHg) than PO2 in tissue cells (40mmHg)
why is the PO2 of systemic capillaries higher than the PO2 of blood in tissue cells?
pressure differences cause O2 to diffuse out of capillaries into tissue cells and blood PO2 drops to 40mmHg by the time blood exits systemic capillaries
what are tissue cells constantly producing as a result of metabolism?
CO2
describe the PCO2 of cells versus PCO2 of capillaries and what this results in
PCO2 of cells (45mmHg at rest) is higher than that of systemic capillary blood (40mmHg) so CO2 diffuses from tissue cells through interstitial fluid into systemic capillaries until PCO2 in blood increases to 45mmHg
what happens after PCO2 in blood increases to 45mmHg?
deoxygenated blood returns to the heart and is pumped to the lungs for external respiration
what percentage of available O2 in oxygenated blood does a person need at rest? what does this mean for the other percentage?
a person at rest needs only appoximately 25% of available O2 in oxygenated blood, so “deoxygenated blood” retains 75% of O2 content
what happens during exercise in terms of available O2?
more O2 diffuses into metabolically active cells
what 4 factors influence the rate of pulmonary and systemic gas exchange?
- partial pressure differences of gases
- surface area available for gas exchange
- diffusion distance
- molecular weight and solubility of gases
what must be true in order for oxygen to diffuse from alveolar air into blood?
alveolar PO2 must be higher than blood PO2 for oxygen to diffuse from alveolar air into blood
what happens to the rate of diffusion as pressure differences increase?
rate of diffusion is faster when pressure difference is greater
when does the differences between PO2 and PCO2 in alveolar air versus pulmonaary blood increase?
during exercise
what does the partial pressure of oxygen and CO2 depend on?
rate of airflow into and out of the lungs
what does increasing altitude do and what does this result in?
increasing altitude decreases total atmospheric pressure and decreased the partial pressure of O2
describe the relationship of PO2 of inhaled air and atmospheric pressure and what this results in for alveolar air and O2 diffusion
PO2 of inhlaed air decreases with increasing altitude and alveolar PO2 drops correspondingly, so O2 diffuses out of blood more slowly
list 5 symptoms of high altitude sickness
- shortness of breath
- headache
- fatigue
- nausea
- dizziness
describe the relationship between surface area and gas exchange
direct
describe the surface area of alevoli
huge, with many surrounding capillaries
what will pulmonary disorders that reduce surface area of respiratory membranes do to external respiration? give an example
will decrease rate of external respiration; pulmonary gas exchange is slowed in emphysema
how is diffusion distance related to rate of pulmonary and systemic gas exchange?
shorter distance means higher rate of diffusion
what minimizes the diffusion distance from alevolar air space to hemoglobin inside red blood cells? (2)
- thin respiratory membrane
- narrow capillaries
describe what pulmonary edema does to rate of gas exchange and why
causes a buildup of interstitial fluid between alveoli, which slows gas exchange because it increases diffusion distance
describe how molecular weight and solubility of gases is related to rate of gas exchange (2)
- lower molecular weight = faster diffusion
- higher solubility = greater diffusion
relate molecular weight and solubility of O2 and CO2 to their relative rates of gas exchange
O2 has a lower molecular weight than CO2, but CO2 is 24x more soluble in the fluid portion of the respiratory membrane than O2, so a net outward diffusion of CO2 occurs 20x more rapidly than net inward O2 diffusion
due to their molecular weights and solubility, when diffusion is slower than normal, as in the case of epmhysema or pulmonary edema, does hypoxia or hypercapnia occur first? why?
O2 insufficiency (hypoxia) occurs before major retention of CO2 (hypercapnia) since CO2 is diffusing outward at 20x the rate that O2 is diffusing inward
in what two ways and proportions is O2 transported within the body?
- 1.5% of inhaled O2 is dissolved in blood plasma
- 98.5% of blood O2 is bound to Hb in RBC
each 100mL of oxygenated blood contain the equivalent of how much gaseous oxygen? list how much is dissolved in plasma and how much is bound to Hb
20mL
0.3mL dissolved in plasma
19.7mL bound to Hb
what does the heme portion of each hemoglobin contain and what does it do and form?
the heme portion of hemoglobin contains 4 iron atoms, each of which can bind a molecule of O2 in a reversible reaction to form oxyhemoglobin
what is the most important factor in determining how muhc O2 binds to Hb and how does this relate?
PO2; the higher the PO2, the more O2 combines with hemoglobin
when is hemoglobin said to be fully saturated?
when reduced hemoglobin is completely converted to oxyhemoglobin
if each hemoglobin molecule has bound 2 O2 molecules, what % saturation?
50%
describe Hb when PO2 is higher
Hb binds with large amounts of O2
describe Hb when PO2 is lower
Hb only partially saturated
describe the PO2 of pulmonary capillaries and what this means to Hb
PO2 is high in pulmonary capillaries so lots of O2 binds to Hb
describe PO2 in tissue capillaries andwhat this means for Hb
PO2 is low in tissue capillaries so Hb does not hold as much O2, and dissolved O2 is unloaded via diffusion into tissue cells
at rest, what % of O2 is unloaded from Hb and used by tissue cells? what does this mean for Hb ar PO2 of 40mmHg?
only 25% of available O2 unloads from Hb at rest, so Hb is still 75% saturated with O2 at PO2 of 40mmHg
what happens between PO2 20-40mmHg?
large amounts of O2 are released from Hb in response to small decreases in PO2
what happens when active tissues in contracting muscules drop well below PO2 of 40mmHg? why?
large percent of O2 is released from Hb to send more O2 to metabolically active tissue
what happens to the affinity of Hb for O2 as acidity increases? what is the result?
as acidity increases the affinity of Hb for O2 decreases and O2 dissociates more readily from Hb
how do metabolically active tissues obtain more O2?
the produce lactic and carbonic acids, which increases acidity and decreases Hb binding affinity for O2 so more O2 is offloaded and sent to metabolically active tissues
what is the Bohr effect? (2)
- an increase in H+ in blood causes O2 to unload from Hb
- binding of O2 to Hb causes unloading of H+ from Hb
provide an explanation for the Bohr effect (3)
- Hb can act as a buffer for H+, but when H+ ions bind to amino acids in Hb, they alter its structure to decrease its O2-carrying capacity
- so lowered pH drives O2 off of Hb, making more O2 available for cells
- but elevated pH increases affinity of Hb for O2 and shifts the oxygen-Hb dissociation curve to the left
how does PCO2 affect Hb binding affinity for oxygen?
similar to H+, CO2 can also bind Hb and cause Hb to release more O2, so as PCO2 rises, Hb releases O2 more readily
how are PCO2 and pH related factors in terms of Hb binding affinity for O2?
- low blood pH results from high PCO2
- as CO2 enters the blood, much of it is temporarily converted to H2CO3, which in red blood cells dissociates into H+ and HCO3-, so H+ increases and pH decreases
how does temperature relate to Hb binding affinity for O2?
as temperature increases, so does amount of O2 released from Hb
when does body heat increase (not sick)
with exercise
what do metabolically active cells, as in exercise, require? how do they get this?
require more O2, so they liberate more acids and heat to decrease Hb binding affinity for O2
what happens with hypothermia?
metabolism slows, and Hb binding affinity for O2 increases and less O2 is offloaded from Hb
what does 2,3-BPG do?
decreases Hb binding affinity for O2; helps unload O2 from Hb
when and where is 2,3-BPG formed?
in red blood cells when they metabolize glucose to form ATP
what happens when 2,3-BPG combines with Hb?
Hb binds O2 less tightly at the heme group sites
what happens as 2,3-BPG level increases?
more O2 is offloaded from Hb
the presence of what 5 things increases formation of 2,3-BPG? what do they all have in common and how does this relate to their increasing 2,3-BPG?
- thyroxine
- HGH (growth hormone)
- epinephrine
- norepinephrine
- testosterone
all increase metabolism, so also increase O2 offloading from Hb
how is CO2 transported in the blood? (3)
- dissolved
- carbamino compounds
- bicarbonate ions
what is the simplest form of CO2 transport in blood and what percent of CO2 is transported this way?
dissolved in blood; 7% of CO2 transported this way
what happens to CO2 that is transported as dissolved in blood once it reaches the lungs?
it diffuses into alveolar air and is exhaled
what percent of CO2 is transported via carbamino compounds?
23%
describe carbamino compounds
CO2 combines eith amino groups off amino acids/protein in the blood
what is the most prevalent blood protein that is also a carbamino compound?
hemoglobin
how is most CO2 that is transported via carbamino compounds transported?
bound to hemoglobin
what are the CO2 binding sites on hemoglobin?
the 2 alpha and the 2 beta globin chains
what is Hb + CO2?
Hb-CO2, or carbaminohemoglobin
what is the formation of Hb-CO2 strongly influenced by?
PCO2
describe how PCO2 influences formation of Hb-CO2 in tissue capillaries
in tissue capillaries: PCO2 is relatively high which favors formation of Hb-CO2
describe how PCO2 influences formation of Hb-CO2 in pulmonary capillaries
in pulmonary capillaries, PCO2 is relatively low so CO2 splits off Hb and enters alveoli by diffusion (for exhale)
what percent of CO2 is transported by bicarbonate ions (HCO3-)?
70%
what happens as CO2 diffuses into systemic capillaries and enters RBCs?
it reacts with water to form carbonic acid, which dissociates into H+ and CO3-
what happens as blood picks up CO2? in terms of bicarbionate ions and downstream effects
- HCO3- accumulates inside RBCs
- some HCO3- moves into blood plasma, down its concentration gradient
- in exchange Cl- move from plasma into RBCs in the chloride shift for charge balance
since the chloride shift happens in systemic capillaries as CO2 diffuses in, what happens in pulmonary capillaries and CO2 diffuses out?
reverse chloride shift
what is the net effect of CO2 increases in the blood and subsequent bicarbonate ion formation and chloride shift in systemic capillaries? what happens in pulmonary capillaries?
CO2 is removed from tissue cells and transported in blood plasma as HCO3-; then as blood passes through pulmonary capillaries in the lungs all these reactions are reversed and CO2 is exhaled
what is the amount of CO2 that can be transported in the blood influenced by?
% saturation with O2
what is the haldane effect?
the lower the amount of oxyhemoglobin, the higher the CO2-carrying capacity of the blood
what 2 characteristics of deoxyhemoglobin lead to the haldane effect?
- deoxyhemoglobin bonds to and therefore transports more CO2 than does Hb-CO2
- deoxyhemoglobin also buffers mroe H+ than does Hb-CO2, thereby removing H+ from solutionand promoting conversion of CO2 to HCO3- by the reaction catalyzed by carbonic anhydrase
which effect (haldane or bohr) does this statement apply to: binding of both H+ and CO2 to oxyHb favors release of O2
Bohr effect
describe deoxyHb affinity for CO2 and H+ compared to HbO2
deoxyHb has a greater affinity for both CO2 and H+ than does HbO2
what does unloading of O2 from Hb in tissue capillaries facilitate?
unloading of O2 from Hb in tissue capillaries facilitates picking up of CO2 and H+ by Hb
which effect does this statement apply to: ability of deoxyHb to pick up CO2 and CO2 generated by H+
haldane effect
how do the bohr and haldane effect work together?
these two effects work synchronously to facilitate O2 liberation and uptake of Co2 and CO2-generated H+ at the tissue level
what does increased CO2 and H+ cause and by what effect?
by the Bohr effect, increased CO2 and H+ causes increased O2 release from Hb
what does increase O2 release from Hb cause and by what effect?
by the Haldane effect, increased O2 release from Hb causes increased CO2 and H+ uptake
what must happen to deoxyHb and why?
deoxyHb must be carried back to the lungs to reload with O2
after O2 is released from Hb, what does Hb do?
after releasing O2, Hb picks up CO2 and H+ that are going in the same direction (to the lungs)
summaarize gas exchange and transport (9)
- deoxygenated blood returing to pulmonary capillaries in lungs contains CO2
- RBCs have picked up H+, some of which binds to and os buffered by Hb
- as blood passes through pulmonary capillaries, molecules of CO2 dissolved in plasma and CO2 that dissociates from Hb diffuse into alveolar air and are exhaled
- at the same time, inhaled O2 is diffusing into RBCs (from alveolar air) and is binding to Hb to form oxyHb
- CO2 is also released from HCO3- when H+ combines with HCO3- inside RBCs
- thw H2CO3 formed from this reaction then spltis into CO2 (exhaled) and H2O
- as concentration of HCO3- declines inside RBcs in pulmonary capillaries, HCO3- diffuses in from blood plasma in exchange for C-
- oxygenated blood leaving the lunds has increased O2 content and decreased amounts of CO2 and H+
- in systemic capillaries, as cells use O2 and produce CO2, the chemical reactions reverse
where is the respiratory center in the brain?
in the medulla oblongata and pons
what 3 controls of respiration are in the medulla oblongata? what are their functions?
- medullary rhythmicity area: controls basic rhythm of respiration
- inspiratory area: basic rhythm of breathing (inhalation)
- expiratory area: inactive in quiet breathing
what does the pons do for control of respiration?
helps coordiante the transition between inhalation and exhalation
what 2 areas in the pons are in control of respiration and what are their functions?
- pneumotaxic area: helps turn off inspiration area before lungs become too full
- apneustic area: sends stimulatory impulses to inspiratory area to prolong inhalation
what happens if the pneumotaxic area of the pons is active?
rapid breathing rate
what happens if the apneustic area of the pons is active?
long, deep inhalation
what triggers rapid breathing?
penumotaxic area overrides apneustic area when the proper stimulus is present
