3.6.2. O2 and CO2 Transport Flashcards
There are 3 parts to the respiratory system what are they?
Conduction zone Respiratory zone Pump
What is the conduction zone
Nasal cavity, Nasopharynx, Larynx, Trachea and bronchi
What is the respiratory zone
Bronchioles and alveoli
What is the pump
Chest wall skeleton/muscles, diaphragm, elastic connective tissue
Major vs. minor functions of respiratory system
Major Function: facilitates the exchange of gases in and out of tissue (provides oxygen and removes carbon dioxide) Minor Functions: vocalization, removal of irritants (coughing/sneezing), and temperature control
Describe the Oxygen transport life cycle and what each phase is called
From atmospheric air to lung alveoli (pulmonary ventilation) From lung alveoli through layers of the respiratory membrane to hemoglobin (simple diffusion) From pulmonary capillaries to tissue capillaries (blood circulation) From hemoglobin to interstitial fluid and tissue cells (simple diffusion)
Describe the CO2 transport life cycle and what each phase is called
From tissue cells to interstitial fluid and blood (simple diffusion) From tissue capillaries to pulmonary capillaries (blood circulation) From blood across respiratory membrane layers to lung alveoli (simple diffusion) From lung alveoli out to atmospheric air (expiration)
Pressure vs. partial pressure
Pressure is the force of molecules against a surface, and thus pressure is directly proportional to the concentration of gas molecules Partial pressure = Total pressure x Fractional Gas Concentration
Why does O2 come into the lungs and CO2 leave?
There is a partial pressure for CO2 in the atmosphere of 0.3 and in the lungs is 40. Following pressure gradients, the CO2 will want to break into the atmosphere (H2O follows this same pathway with similar pressure changes) For 2, it has atmospheric pressure of 159 and a lung pressure of 104, making it go into the lungs
What is Henry’s Law?
Henry’s Law: the amount of a given gas dissolved in a liquid is directly proportional to the partial pressure of that gas in equilibrium with that liquid
Henry;s law is complex, but what is it basically saying?
More soluble = higher concentration of gas Less soluble = lower concentration of gas
Partial pressure =
concentration/solubility
Carbon dioxide is ___ times ____ (more/less) soluble than oxygen
Carbon dioxide is >20 times more soluble than oxygen
If CO2 is more than 20X soluble than oxygen, what does that mean the state of gasses will be for a given partial pressure?
AKA at a given partial pressure, the concentration of carbon dioxide molecules is 20 times greater than oxygen molecules
Solubility coefficients for common gasses
Oxygen = 0.024; Carbon dioxide = 0.57; Carbon monoxide = 0.018; Nitrogen = 0.012; Helium = 0.008
The greater the solubility of a gas, _______________________.
The greater the solubility of a gas, the greater number of molecules available to diffuse
Factors that affect diffusion rate proportionally:
Solubility of the gas in fluid; Difference in partial pressure between compartments; Cross-sectional (surface) area for diffusion; Temperature
Factors that affect diffusion rate inversely:
Square root of the molecular weight of the gas; Distance of diffusion
Diffusion of oxygen between alveolar air and blood in pulmonary capillaries is ____
Diffusion of oxygen between alveolar air and blood in pulmonary capillaries is rapid
Diffusion of oxygen between alveolar air and blood in pulmonary capillaries is rapid Why?
- Cross-sectional (surface) area for diffusion 2. Distance of diffusion Anatomic structures are optimized for these two factors Pulmonary capillary blood volume = 65-100 mL Alveolar surface area = 70-100 square meters
True or False: One of the important factors in transport is diffusion
Driven by cardiac force; blood is pumped to peripheral tissues; diffusion is not significant in transport
_____ of oxygen transported in blood is dissolved in either plasma or the RBC cytoplasm (low solubility compared to carbon dioxide)
Only 3% of oxygen transported in blood is dissolved in either plasma or the RBC cytoplasm (low solubility compared to carbon dioxide)
_____ of oxygen is transported in RBCs bound to hemoglobin _____% of all proteins in a RBC are hemoglobin _______ molecules of hemoglobin in each RBC
Remaining 97% is transported in RBCs bound to hemoglobin 95% of all proteins in a RBC are hemoglobin 280 million molecules of hemoglobin in each RBC
How many and what types of chains are found in hemoglobin?
2 alpha and 2 beta
Discuss allosteric binding as it pertains to hemoglobin
Binding causes a conformational change to allow for easier binding of the next oxygen molecule to a different unoccupied heme group in hemoglobin
Factors that alter oxygen-hemoglobin dissociation curve
Hydrogen ions Carbon dioxide Temperature 2,3-bisphosphoglycerate
Hydrogen ions Carbon dioxide Temperature 2,3-bisphosphoglycerate These factors alter the oxygen-hemoglobin dissociation curve. What do they do?
An increase in any of these factors results in a decrease of hemoglobin affinity for oxygen: CURVE SHIFTS TO THE RIGHT All of these factors increase during exercise
Discuss the Bohr effect
Peripheral tissues are using oxygen and producing CO2. Increased CO2 leads ot increased hydrogen ions (Bohr Effect)
Formula for how CO2 changes
pH in the tissues vs in the lungs
Tissues pH = 7.2
Lungs pH = 7.6
Discuss how a hemoglobin saturation curve changes due to pH
Diffusion to Peripheral Tissues is driven by what
Driven by partial pressures between arterial capillary and interstitial fluid
Minimal PO2 requirement for biochemical processes in cells ranges from ____ to ____
Minimal PO2 requirement for biochemical processes in cells ranges from 1-3 mmHg
During physiological conditions where oxygen demand is significantly increased, the respiratory system can still supply enough oxygen so that intracellular PO2 is not below ____.
During physiological conditions where oxygen demand is significantly increased, the respiratory system can still supply enough oxygen so that intracellular PO2 is not below 5 mmHg
Discuss the issue with oxygen supply we see at higher altitudes and why that occurs
Altitude = less barometric pressure
Oxygen at 5000 feet (120 mmHg); On Mt Everest (36 mmHg)
How and why does CO cause poisoning?
CO binds to hemoglobin with 200x more affinity than O2
Rely on Plasma O2 transport (remember 3% of oxygen is carried this way)
Discuss oxygen changes with anemia
Anemia = change in oxygen carrying capacity
May be compensated by cardiac output
Why is fire dangerous in regards to oxygen?
Fires = oxygen consumed
___ ____ is responsible for oxygen transport to peripheral tissues. ___________________ govern transport
Simple diffusion is responsible for oxygen transport to peripheral tissues. Differences in oxygen partial pressures govern transport
Discuss the mechanisms and where they locate for CO2 transport in the blood.
_____ mL of carbon dioxide is transported from tissues to the lungs per 100 mL of blood
4 mL of carbon dioxide is transported from tissues to the lungs per 100 mL of blood
In what forms is CO2 transported and in what degrees?
Dissolved CO2 (7%)
Carbamino compounds (23%)
As bicarbonate atoms (70%)
Carbon dioxide reacts with water to form carbonic acid which dissociates into bicarbonate and hydrogen ions
Where does this occur and at what speed and why?
Occurs SLOWLY in PLASMA, but RAPIDLY in RBC because of the enzyme carbonic anhydrase (~5,000 times faster)
How does Bicarbonate leave the cell? What does this cause?
Bicarbonate leaves the cell via a bicarbonate-chloride exchanger protein (aids in further dissociation of carbonic acid)
Facilitated diffusion (i.e., no energy is utilized)
Chloride maintains electroneutrality
Chloride shift = RBCs in venous blood have higher intracellular chloride ion concentrations than in arterial blood
Carbon dioxide may also react with proteins instead of water (no enzymatic activity is present)
Where does this occur and why?
RBCs
Protein concentration is greater in RBCs
Hb forms carbamino compounds more easily
Hb is a buffer for the H+ that is produced
What is the Haldane Effect?
Oxygen binding to hemoglobin causes carbon dioxide to be released from the blood more effectively
Oxygen binding to Hg makes it become a ____ ____; released hydrogen ions bind with _____ and form carbonic acid which dissociates into ____ and _____.
Oxygen binding to Hg makes it become a stronger acid; released hydrogen ions bind with bicarbonate and form carbonic acid which dissociates into CO2 and water
Oxygen binding to ______________ displaces the _____ from it directly
Oxygen binding to carbaminohemoglobin displaces the CO2 from it directly
Effects of CO2 on blood pH
Carbonic acid (formed first) has an effect on blood pH
Changed from 7.41 in arterial blood to 7.37 in venous blood
When do we see respiratory acidosis?
Decreased alveolar ventilation (drug overdose)
Lung-diffusing capacity (pulmonary edema)
Decreased diffusion (acute respiratory distress)
Increased arterial PCO2 → what?
How does the body respond?
Increased arterial PCO2 → Increased H+ and HCO3- → lower pH
Arterial PCO2 > 44 mmHg
Blood pH < 7.35
Renal system compensatory mechanism will increase HCO3- to return blood pH to normal levels (Increase HCO3- leads to the reverse reaction, causing more CO2 and thus less H+)
When do we get respiratory alkalosis?
Response to hypoxia, anxiety, drug toxicity, and fever
Decreased arterial PCO2 → what?
How does the body respond?
Decreased arterial PCO2 → Decreased H+ and HCO3- → higher pH
Arterial PCO2 < 35 mmHg
Blood pH > 7.45
Renal system compensatory mechanism will decrease HCO3- to return blood pH to normal levels
Hemoglobin disassociation curves for being at rest vs. exercise
