respiratory phys Flashcards
Innervation of the lungs
1) Parasympathetic: CONSTRICTS bronchioles, via ACh and AM3-Gq coupled receptors
OR via substance P, which also constricts bronchioles
- dynorphin or VIP release will relax, dilate the system via Gs or guanylyl cyclase activation, but this is a minor action.
2) Sympathetic: does NOT innervate bronchioles, innervates the glands directly, stimulates secretion
3) hormonal adrenergic activation of bronchiole Beta-receptors, DILATES small airways and vessels via beta-2 receptors, also stimulates secretion of bronchiolar glands
3) nonadrenergic, noncholinergic inhibitory/relaxing system
4) nonadrenergic, noncholinergic stimulatory/constricting system
What are the Inspiratory and Expiratory muscles
Inspiration: diaphragm, external intercostals, scalenes
Expiration: Internal intercostals, abdominals muscles
What are the PO2 and PCO2 values in the :
Trachea
Alveolus
Artery
Vein
What is the water vapor pressure at body temperature?
Trachea:
PO2 = 150
PCO2 = 0
Alveolus
PO2 = 100
PCO2 = 40
Artery
PO2 = 95
PCO2 = 40
Vein
PO2 = 40
PCO2 = 46
Water vapor pressure at 37C
47mmHg
Ventilation perfusion ratio
what is the average for the total lung
what are the regions
= alveolar ventilation / blood flow
average is 0.8 for total lung
What equation can estimate physiologic dead space
The Bohr equation
Vd = Vtotal x ((40mmHg x PCO2expired) / 40mmHg)
What is the alveolar gas equation
estimates the alveolar PO2 from the known inspired air O2 concentration, the 40mmHg alveolar PCO2, and the respiratory quotient
PalvO2 = PinspO2 - (PalvCO2/RQ)
What is the chloride shift of an RBC?
The accumulation of chloride in RBCs as they move from arteries to veins
The Cl-/HCO3- exchanger, which pumps bicarbonate out and chloride into the RBC.
This helps the RBC unload O2 at areas of high CO2 concentration
How is CO2 transported to the lungs? What are the fractions?
65% as HCO3- bicarbonate generated within RBCs by carbonic anhydrase
5% as HCO3- within plasma due to natural dissociation
20% as Hgb-CO2 weakly bound
5% as CO2 dissolved in in solution within the RBCs
5% is in the plasma as H2CO3 undissociated bicarbonic acid.
What is the Bohr effect?
The rightward shift of the Hgb oxygen saturation curve, which occurs in the capillaries/veins/deoxygenated areas
due to: increased Hydrogen ions increased CO2 increased temperature increased BPG
The shift then occurs in reverse in the lungs
What is the Haldane effect?
The DOWNward shift of the Hemoglobin-Carbon Dioxide binding curve,
The effect where the high O2 concentration in the lungs expels CO2 molecules bound to hemoglobin.
What are the respiratory regulation nuclei in the brain
The dorsal respiratory center = the Nucleus of Solitary Tract. It sends gradually increasing ramp signals to the Spinal cord to activate inspiratory muscles.
Pneumotaxic Center: Inhibits the Dorsal respiratory center, the OFF switch to inspiration.
can be activated at higher frequencies in order to shorten inspiration and increase overal breathing rate.
The nucleus parabrachialis, at the level of superior cerebellar peduncle.
The Ventral Respiratory Center
Not very involved in normal rythmic breathing
Three separate nuclei in the medulla, not active during normal breathing, but can be active as when very rapid breathing is neccessary. Contains multiple types that can activate or inhibit respiration in order to speed up the overall rate.
What is the Herring/Breuer Reflex
The stretch reflex of the lung, activated when the lung is stretched to about 3 times the tidal volume, probably as a protective reflex.
Activates pneumotaxic center and inhibits the dorsal respiratory center.
Where is the chemosensitive area of the brain’s respiratory control system?
What does it sense and regulate?
It is a bilateral region, called the chemosensitive area, just beneath the VENTRAL surface of the medulla.
It is stimulated indirectly by increased CO2 concentration in the blood, due to the increased H+ ions produced by CO2 after it has diffused into the CSF.
The chemosensitive area then regulates the respiratory center to potently increase the strenght of inspiratory and expiratory signals when pH has dropped in the CSF.
It is not sensitive to O2 concentrations
Where are the peripheral chemosensor areas regulating respiration?
What do they detect?
In the Carotid Sinus and Aortic Arch.
They receive their blood from their own small nutrient bodies, and not the large vessels which they lie on to detect pressure.
They receive extremely high flow, so that they can detect blood that has virtually not lost any O2, and are detecting arterial blood PaO2.
If the PO2 falls below ~90mmHg the chemoreceptors become activated,
and then their activation curve increases very sharply up towards its maximum below 60 mmHg , as below this value the Hgb saturation curve is starting to drop sharply.
As long as O2 is above 100mmHg they do not affect ventilation rate,
and only reallly begin to affect it strongly once O2 has dropped below 60mmHg.
the effect of low O2 to increase respiration is strongly BLUNTED if PaCO2 levels are lower than 40mmHG, and strongly POTENTIATED if PaCO2 is 45mmHg or higher
At normal PaO2 levels, a 10mmHG change in PaCO2 causes how much of an increase in Alveolar ventilation?
a 3-fold increase.
