Respiration stuff Flashcards
What’s the rate of ventilation and perfusion when they are matched?
alveolar ventilation: 5 L/min
pulmonary blood flow: 5 L/min
What is gravity’s effect on ventilation and perfusion?
Bottom of the lung is ventilated more than the top of the lung.
More blood flow to the bottom than the top of the lungs.
What is the difference between anatomical dead space and physiological dead space?
Anatomical dead space: areas where air is moving in and out of passages but does not reach respiratory surfaces (e.g. mouth, trachea)
Physiological dead space: alveoli that are ventilated but not perfused, or perfused but not ventilated
In a normal, healthy, resting person, how long does it take capillary blood hemoglobin to saturate with oxygen on its travels through the lung capillary bed?
It takes 0.25 seconds, or one-third of the travel distance through the capillary bed, to saturate the hemoglobin
What is the difference in time it takes for blood to traverse lung capillary beds between at rest and exercising?
Cardiac output at rest: blood takes about 0.75 seconds to traverse the lung capillary beds
Exercising cardiac output: blood takes about 0.25 seconds to traverse the lung capillary beds
How is oxygen carried in the blood?
Of the 200 mL of oxygen per liter of blood:
3 mL dissolved in plasma
197 mL (98.5%) is bound to hemoglobin
What’s one reason that oxygen mostly binds to hemoglobin in the blood instead of floating freely in plasma?
You want to transport a lot of oxygen in order to supply body tissues, but you want the oxygen gradient actually in the plasma to be very low in order to create a nice diffusion gradient between the alveoli and the lung capillaries. Having practically no oxygen in the plasma helps oxygen to diffuse into the plasma at the alveoli from oxygen in the inhaled air, and as soon as oxygen reaches the plasma, it is bound to hemoglobin, thus maintaining the very low concentration and good gradient in order to keep drawing in more oxygen.
On average, what is the saturation of hemoglobin with oxygen in venous blood?
On average, each hemoglobin in venous blood has 3 of 4 possible oxygen sites bound
(75% saturation at 40 mm O2)
What is the impact of exercise on hemoglobin saturation?
All changes induced by exercise (lower pH, temp, CO2, etc) cause a rightward shift of the hemoglobin saturation curve.
Meaning, oxygen leaves hemoglobin more freely and at 40 mm Hg of O2 in venous circulation, on average the saturation will be below 75% (normal).
What is the difference between the reaction of skeletal smooth muscle and the reaction of pulmonary smooth muscle to low oxygen?
Skeletal smooth muscle responds to lower oxygen by dilating (bring in more blood = more oxygen!).
Pulmonary smooth muscle responds to lower oxygen by constricting (why bother perfusing this area that’s not getting much oxygen to it?).
What is the dominant form of CO2 carried in the blood?
60% bicarbonate HCO3-
30% attached to hemoglobin
10% freely dissolved in plasma
What ion is antitransported with bicarbonate when bicarbonate is moved out of RBC into plasma?
Cl- is moved into RBC from plasma when HCO3- is moved out of RBC into plasma
What is the fundamental equation of acid-base balance?
CO2 + H2O ⇆ H2CO3 ⇆ H+ + HCO3-
Where is the respiratory pattern generator located (speaking broadly)?
medulla of brainstem
What are the two respiratory groups of the medulla and what general neurons do they contain?
Dorsal Respiratory Group: inspiratory neurons
Ventral Respiratory Group: inspiratory neurons AND expiratory neurons
What is the specific name of the area of the medulla that contains the respiratory rhythm-generating neurons?
Pre-Bötzinger complex of the Ventral Respiratory Group
What are the two peripheral chemoreceptors?
carotid body
aortic body
What nerves supply the carotid body and the aortic body?
carotid body: glossopharyngeal nerve
aortic body: vagus nerve
In terms of O2, what is the carotid body sensing?
Carotid body is sensing DISSOLVED O2. Carotid body has no idea how much O2 is attached to hemoglobin or how much hemoglobin there is (e.g. anemia).
What is the hypoxic threshold where the receptors in the carotid body really begin to discharge (signal the CNS)?
Around 70 mmHg of O2. Above this the receptors don’t really signal, and below this they increase their signal accordingly.
What do the central chemoreceptors sense and what do they not sense?
Central chemoreceptors sense pCO2 and pH (H+). They are not oxygen sensors.
Where is the largest concentration of respiratory central chemoreceptors?
On the ventral surface of the medulla
How can central chemoreceptors respond to pH when H+ cannot cross the blood-brain barrier?
CO2 in CSF CAN cross the BBB, and carbonic anhydrase in the brain converts the CO2 into pH
What three changes may stimulate the peripheral chemoreceptors to signal the CNS?
- hypoxia - decreased plasma O2
- metabolic acidosis - increased H+
- respiratory acidosis - increased PCO2
