Lecture 18 - Control of Breathing Flashcards
What Determines the PA (Partial Pressure) of a Gas?
Ambient Pgas (Patm x Fgas)
Cell usage (O2) and production of (CO2) → metabolic rate
Ventilation rate
what happens if we increase alveolar ventilation without changing metabolism
O2 increases and CO2 decreases
what happens if we increase metabolism without changing ventilation
O2 decreases and CO2 increases
what is hyperventilation
If ventilation goes above metabolism
Control of Respiration Regulated by
O2, CO2, and H+ in the blood
what are the sensors called that recognize O2,co2, and H+ chemicals changes
chemoreceptors
what are the sensors called that recognize O2,co2, and H+ chemicals changes
chemoreceptors
what are teh 2 categories of chemoreceptors
Peripheral (aortic & carotid bodies)
arterial
Carotid dominates
Central (medulla)
Interstitial fluid
Right inside the brain
what is the Hering-Breuer reflex
Triggered to avoid overinflation of lungs
Activates slow-adapting receptors
Classic negative feedback loop
This reflex occurs with literally every breath you take to make sure you don’t over inflate your lungs
Changes in VE are minimal until PaO2 < ____ mmHg
60
Why Does Ventilation Not Change Until the Arterial PO2 < 60 mmHg?
Has to do with the O2 Hb dissociation curve
As long as our Hb is saturated, we don’t need to increase O2 and we are almost fully saturated up until 60mmHg (↑ VE doesn’t always mean ↑ Hb saturation; depends on PO2 of blood)
However, small changes in PaCO2 cause large changes in VE
Peripheral chemoreceptors actually respond to H+, not CO2 directly (on its own, CO2 is a ‘weak’ stimulus)
O2 is a ‘weak’ stimulator of ventilation
For every 1 CO2 produced, we produce 1 O2
Central Chemoreceptors
Senses changes within the extracellular fluid of the brain
Responds to changes in H+ (pH) in the medulla
The central chemoreceptor responds to changes in PaCO2
The carotid body is sensing the partial pressure of o2 not the saturation ***
the carotid body is sensing the partial pressure of o2 not saturation
