Phys: Diffusion And Transport Of Gas Flashcards
How does gas exchange in the lung occur?
By simple diffusion
What does diffusion of gas depend on? (3 things)
-pressure gradient of the gas
-surface area
-thickness
What is partial pressure?
The pressure exerted by each individual gas in a mixture
A gas will dissolve in _______ in proportion to its ______________
Fluid, partial pressure
Which partial pressures drive the diffusion across the respiratory membrane?
PO2 and PCO2
A _______ PO2 gradient exits across the respiratory membrane. What does this cause?
large, oxygen to diffuses rapidly from alveoli into pulmonary capillary blood
PCO2 gradient diffuses in the opposite direction under a ________ pressure gradient. What does this cause?
Smaller, equal amounts of O2 and CO2 are exchanged
What is the PO2 in the alveoli? Pulmonary arteries?
Alveoli - 104mmHg
Pulmonary arteries - 40mmHg
What is the PCO2 in the alveoli? Pulmonary arteries?
Alveoli - 45mmHg
Pulmonary arteries - 40mmHg
Which law determines gas transferred/unit time?
Fick’s law
What happens when the surface area is decreased?
Decreases in gas exchange
What diseases can decrease surface area?
Degenerative lung diseases and pulmonary embolism
What happens if the thickness of the membrane increases?
Gas exchange takes longer
What does the amount of oxygen delivery depend on?
-function of circulatory and respiratory systems
-blood flow to tissues
-oxygen content of blood
-oxygen consumption by the tissues
What happnes to oxygen carrying capacity in anemia?
Oxygen carrying capacity decreases
What is oxygen carrying capacity?
The maximum amount of oxygen that can bind to the hemoglobin
What is the normal oxygen carrying capacity?
20 mL O2/dL of blood
What is oxygen content?
The sum of oxygen bound to hemoglobin and oxygen in free form (dissolved form) in each 100 mL of blood
What is hemoglobin saturation?
Percentage of hemoglobin present as oxyhemoglobin
What are the two forms that oxygen can be transported in the blood?
-dissolved in plasma (1.5-2%)
-bound to hemoglobin (98-98.5%)
What does Henry’s law say?
The amount of gas that dissolves in a liquid is proportional to the partial pressure of the gas in contact with the liquid
What is hemoglobin?
The oxygen carrying protein within the red blood cells
How many molecules of hemoglobin are in each cell?
250 million molecules
Hb [ ] in males
14-18 g/dl
Hb [ ] in females
12-16 g/dl
What is the Main function of Hb?
Transport of oxygen and carbon dioxide
What is Hb composed of?
A heme portion and a globin portion
What is located in the heme part of Hb?
4 heme groups that contain iron where O2 can bind
What is in the globin portion of Hb?
4 polypeptide chains in two pairs
What are the 2 polypeptide chains in HbA?
2 alpha and 2 beta chains
What are the two polypeptide chains in HbA2?
2 alpha and two delta chains
(Maybe not delta idfk Greek letters)
What are the two polypeptide chains in HbF?
2 alpha and 2 gamma chains
Which Hb has a greater affinity for O2?
HbF
How many oxygen molecules can each Hb molecule bind?
4
What happens to the affinity of Hb to O2 as it binds more O2?
Affinity increases with each molecule of O2 that binds
What happens if iron on Hb is in the oxidized state?
It is unable to bind O2 and is called methemoglobin
What is oxygen saturation?
The percentage of Hb that is present as oxyhemoglobin
When Hb is fully saturated, how many mL of O2 can each gram of Hb bind?
1.34 mL
What is the shape of the oxygen-hemoglobin dissociation curve normally?
Sigmoid shaped
What happens if the curve shifts towards the right side?
There is a decrease in affinity and oxygen is released
What happens when the curve is shifted towards the left?
There is increases affinity of Hb for oxygen and more loading of oxygen
What factors cause a right shift and O2 offloading?
-increased temp
-increased hydrogen
-increased CO2
-high 2,3 DPG
What factors cause a left shift and more loading of oxygen?
-decreased temperature
-decreased hydrogen
-decreased CO2
-low 2,3 DPG
What happens to the curve when you reduce pH?
The curve shifts to the right, decreased affinity and more offloading
What happens to the curve when you increase 2,3 DPG?
The curve shifts tot the right and increases O2 offloading
What type of binding occurs in hemoglobin-oxygen bond?
Cooperative binding
What happens in carbon monoxide poisoning?
CO binds Hb 200x stronger than O2, so CO poisoning significantly reduces the ability of Hb to carry O2
Which direction does CO poisoning shift the curve?
Towards the left because it stabilizes the relaxed state of Hb
Which direction does HbF shift the curve?
Towards the left, since there is higher affinity for O2 in HbF than HbA
What causes the poor binding of 2,3 BPG in HbF?
2,3-BPG cannot bind to the gamma chains in fetal hemoglobin
What does the high affinity of HbF cause?
Hypoxia, which leads to increased rbc formation
Why is it important for HbF to have a higher affinity for oxygen?
So the fetus can get enough oxygen from the mother during pregnancy
What happens to Hb and O2 content in polycythemia?
Hb increases and O2 increases
What happens to Hb and O2 content in anemia?
Hb decreases and O2 content decreases
What happens to Hb and O2 content in CO poisoning?
Hb normal, and O2 content decreases
___% of CO2 is transported as dissolved CO2
10%
____% of CO2 is transported as carbamino compounds (bound to protein)
20%
___% of CO2 is transported as bicarbonate
70% - main form of transport
**know transport of CO2 in blood
What two factors control respiration?
-neural factors (involuntary and voluntary control)
-chemical factors
What nerves come from the LMN in the cervical segments?
Phrenic nerve that innervates diaphragm
What nerves come from the LMN in the thoracic segment?
Intercostal nerves that innervate intercostal muscles
What is the respiratory center?
A functionally integrated collection of neurons that are located at different levels of the CNS and participate in control of respiration
What is the basic rhythm of respiration generator from the medullary respiratory rhythmicity center?
Dorsal respiratory group
What is the other group from the medullary rhythmicity center?
Ventral respiratory group
What inhibits inspiration and regulates volume and rate of respiration?
Pneumotaxic center
What happens if damage to pneumotaxic center?
Irregular respiration patterns
Where is pneumotaxic center located?
Upper pons
What do chemoreceptors do?
Detective changes in partial pressure of carbon dioxide, partial pressure of oxygen, and pH in the blood or CSF and send feedback to respiratory centers to modulate the breathing pattern to maintain proper levels
Where are peripheral chemoreceptors located?
Carotid and aortic bodies
What are peripheral chemoreceptors stimulated by?
Low PO2 (hypoxia)
Where are the central chemoreceptors located?
The medulla
What stimulates the central chemoreceptors?
-high PCO2 (hypercapnia)
-high [H+]
What is the ventilators response to decreased PO2? What does it result in?
Hyperventilation, results in decreases PCO2 and increased PO2
