Midterm Chapter 17 & 18 Flashcards
Describe the structure of the respiratory membrane including tissues present.
simple squamous epithelium lining the alveoli, endothelium of the pulmonary capillary walls and fused basement membrane
What is the pressure in the pulmonary trunk?
25/8 mmHg
What is the flow rate of blood through the pulmonary circuit?
5L/min
Explain why the pressure in the pulmonary circuit is much lower than the systemic circuit. Explain what would happen if the pressure was the same.
the lower pressure allows for effective contact between the blood and the respiratory structures of the lung, and thus to make possible gas exchanges with the outside air.
If the pressure were the same then the lung would be considerably wetter than it is, and the exchange of gases across the layer of fluid outside the capillary would be slowed.
What is the partial pressure of oxygen in the alveoli?
100mmHg
What is the partial pressure of oxygen in the venous blood?
40mmHg
What is the partial pressure of CO2 in the alveoli?
40mmHg
What is the partial pressure of CO2 in venous blood?
45mmHg
List the 4 main gases found in atmospheric air. Which are the 2 that make up most of our atmosphere? What percent of the air does each contribute?
O2 = 21% CO2 = 0.03% N2 = 80% H2O = variable
Is O2 or CO2 easier to exchange? Why?
O2 because it has a larger pressure gradient
Explain what lung compliance is. Why is compliance important?
the ability to stretch “ease of filling”
-important because lungs need to be able to expand to fill with air.
Explain what elasticity is. Why is elasticity important?
the ability to recoil
-important because lungs need to be able to return to their resting position in able to move inhaled air out of the lungs.
The protein that carries O2 in the blood is what? How many O2 molecules does one of these proteins carry?
Hemoglobin
Each hemoglobin carries 4 oxygen molecules
What are the 2 ways that O2 is carried in the blood? For each list the percent carried in this way.
- Dissolved in plasma ~1%
2. Binds to hemoglobin ~99%
What is the most important factor that determines whether O2 is being bound to or released from hemoglobin?
The partial pressure of O2 determines binding/unbinding.
low PO2 = unbinding: example - Lungs PO2 = 100mmHg = binding / Tissue PO2 = 40mmHg = unbinding
With respect to the blood, explain what percent saturation is.
A measure of how much oxygen the blood is carrying as a percentage of the maximum it could carry.
What are the three major factors (other than PO2) that influence O2 binding/unbinding? Describe the mechanism behind the change in affinity that hemoglobin has for O2.
- Decrease in pH = increase in H+ = extra unloading - the Hydrogen binds to the hemoglobin causing the O2 to unbind.
- Increase in Temp = increase in MR = extra unloading - Increase temp causes increase movement which causes more instability and the O2 unbinds
- Increase in CO2 = extra unloading - CO2 binds to the hemoglobin causing the CO2 to unbind
List the three ways that CO2 is transported in the blood. For each list the percent of the CO2 that is carried in that way.
- Simply as CO2 ~10%
- Bound to hemoglobin ~ 20%
- Bicarbonate ions in plasma ~70%
Describe how CO2 moves into or out of an RBC. Describe how CO2 moves out of an RBC into the alveolar air.
The PCO2 (partial pressure of CO2) is what moves CO2 into or out of an RBC and out of an RBC into the alveola.
Write out the complete chemical equation that describes what happens to CO2 when it reacts with water. List the enzyme that ensures this reaction happens quickly.
CO2 + H2O -> H2CO3 (carbonic acid) -> H+(hydrogen) +HCO-3(bicarbonate)
Enzyme - Carbonic Anhydrase
The part of the brain that sets a basic pattern of ventilation is the what?
Medullary respiratory centers
Are any motor commands required for quiet inspiration? Explain.
Yes. The diaphragm and external intercostals must contract and raise.
Are any motor commands required for expiration? Explain.
No. Not quiet expiration. It is just the relaxation of the diaphragm and external intercostals.
Of the chemoreceptors that feed sensory info into respiratory centers the most important are the what(1)? These are located in the what(2)? These sensory neurons directly monitor the concentration of hydrogen in the what(3)?
- Central chemoreceptors
- located in the medulla
- interstition (cerebrospinal fluid)
Explain how the concentration of hydrogen is related to the arterial PCO2.
An increase in [H+] reduces the pH and the body responds by trying to increase the plasma [HCO3-] (bicarbonate) to match the increase in PCO2 and thus maintain the PCO2/HCO3- ratio; Increased [H+] = Increased PCO2. (Respiratory acidosis)
A decrease in [H+] elevates the pH and the body responds by trying to reduce the plasma [HCO3-] (bicarbonate) to match the reduction in PCO2 and thus maintain the ratio; Decreased [H+] = Decreased PCO2 (Respiratory alkalosis)
- Increases in arterial PCO2 will (increase/decrease) the hydrogen ion concentration of the cerebrospinal fluid.
- This will (increase/decrease) the pH of the cerebrospinal fluid.
- The compensatory response will be (increase/decrease) in ventilation.
- increase
- decrease
- increase
- Decreases in arterial PCO2 will (increase/decrease) the hydrogen ion concentration of the cerebrospinal fluid.
- This will (increase/decrease) the pH of the cerebrospinal fluid.
- The compensatory response will be (increase/decrease) in ventilation.
- decrease
- increase
- decrease
The peripheral chemoreceptors that influence respiration are the (what) and (what)?
carotid and aortic bodies
The peripheral chemoreceoptors sense what qualities of the arterial blood? There are three - which is most important?
- H+ (most important)
- O2 (least important)
- CO2
List the primary sources of Hydrogen ions in the arterial blood. For each, give an example of a situation when H+ concentration would increase due to that source.
- Lactic acid would increase H+ and decrease pH during exercise (acidosis)
- Ketone bodies would increase H+ and decrease pH during fasting (acidosis)
The carotid bodies are most sensitive to (1. what) in arterial blood? They become active only when levels of (2. what gas) reach about (3. what)?
- pH
- H+
- 40mmHg
Generally speaking how important are the peripheral chemoreceptors compared to the central chemoreceptors?
a lot less important
Normal range of arterial blood pH is what?
7.35 - 7.45
the condition where arterial blood pH is below normal is called what?
Acidosis
The condition where arterial blood pH is above normal is called what?
Alkalosis
The condition where arterial blood pH is below normal due to accumulation of CO2 is called what?
Give an example of a situation where a patient might develop this condition.
Respiratory Acidosis
lungs can’t remove enough CO2. This may be due to a decrease in respiratory rate or decrease in air movement due to an underlying condition such as asthma, COPD, pneumonia, or sleep apnea. Some drugs can also cause this.
The condition where arterial blood pH is below normal due to a decrease in CO2 is called what?
Give an example of a situation where a patient might develop this condition.
Respiratory Alkalosis
occurs when carbon dioxide levels drop too low. This causes the pH of the blood to rise and become too alkaline. Caused by hyperventilation
The condition where arterial blood pH is below normal due to some other cause besides accumulation of CO2 is called what?
Give an example of a situation where a patient might develop this condition.
Metabolic Acidosis
production of excess metabolic acids such as lactic acid or ketone bodies; liver failure
The condition where arterial blood pH is above normal due to some other cause besides accumulation of CO2 is called what?
Give an example of a situation where a patient might develop this condition.
Metabolic Alkalosis
Excessive vomiting, excessive base intake such as antacids, some diuretics
Hyperventilation during a panic attack for example, causes arterial PCO2 to (1. increase/decrease/no affect), hydrogen ion concetration to (2. increase/decrease/no affect), and pH to (3. increase/decrease/no affect).
- decrease
- decrease
- increase
Hypoventilation during an overdose of morphine (CNS depressant) for example, causes arterial PCO2 to (1. increase/decrease/no affect), hydrogen ion concetration to (2. increase/decrease/no affect), and pH to (3. increase/decrease/no affect).
- increase
- increase
- decrease
How does the respiratory system compensate for acidosis?
Get rid of [H+]!
Increase ventilation depth and/or rate
How does the renal system compensate for acidosis?
Get rid of [H+]!
Secretion of H+ from blood into filtrate;
production of new HCO-3
How does the respiratory system compensate for alkalosis?
Get rid of HCO-3!
Decrease ventilation depth
How does the renal system compensate for alkalosis?
Get rid of HCO-3!
Less HCO-3 is reabsorbed (retain [H+] and excrete bicarbonate) - more bicarbonate in urine
The non-linear relationship between PO2 and percent saturation is significant for a number of reasons. Explain the relationship between about 80 and 100 mmHg, then explain its significance.
There is not a significant change in percent saturation when pressure changes (flat line)
This is significant because it accommodates decrease in lung function and it allows for elevation.
