Respiratory 2 Flashcards
4 laws
Boyles
Daltons
Henrys
Ficks
Boyles law
P1V1=P2V2
Daltons law
Partial P of gas is the P that gas would exert if it occupied the entire volume of the mixture
Partial pressure of O2
159 mmHg
21% of 760 mmHg
Henrys law
Pp liquid = Pp gas
If alveolar PO2=100 mmHg, also arterial PO2=100 mmHg
Ficks law
Transfer of gas across membrane is due to simple diffusion
Driven by difference in partial pressure
Which gas diffuses faster?
O2
CO2
CO2
Forms of gases in the blood
Free
Bound
Chemically modified
Which gas is never bound/chemically modified?
Nitrogen
Give example of chemically modified gas?
CO2 into bicarbonate
Inspired air gas composition
O2= 158 mmHg CO2= 0.3 mmHg H2O= 5.7 mmHg N2= 596 mmHg
Right heart gas composition
O2= 40 mmHg CO2= 46 mmHg
Left hear gas composition
O2= 95 mmHg CO2= 40 mmHg
Expired air gas composition
O2= 116 mmHg CO2= 32 mmHg
Gas flow can be limited by two things
Diffusion limited
Perfusion limited
Pulmonary blood flow=
CO
Describe pulmonary circulation
Much lower pressure than systemic circulation
What happens in the circulation in response to decrease O2?
Systemic- vasodilation
Pulmonary- vasoconstriction
Why hypoxia causes vasoconstriction in the pulmonary circulation?
Poor ventilated alveoli- capillary around it will constrict (so blood will go to a better alveoli)
V/P ratio in the lungs=
0.8
Alveolar ventilation is 80% of the pulmonary blood flow
what is the location of the respiratory center?
Brain stem
what are the 4 components of the respiratoey controll system?
- chemoreceptors for O2, CO2, H+
- mechanoreceptors in the lungs and joints
- control centers for breathing in medulla and pons
- respiratory muscles
what do the central chemoreceptors sense?
[H+] in ECF/CSF
reflects the PaCO2
**75% of the ventilatory drive at rest
what do the peripheral chemoreceptors sense?
PaO2 (mainly!!)
PaCO2
pH
[K+]
**25% of the ventilatory drive at rest
Inspiratory center is located at
DRG
Dorsal Respiratory Group
Expiratory center is located at
VRG
Ventral
what does the Inspiratory center contol?
basic rhythm by setting the frequency of inspiration
from where do the Inspiratory center get sensory input?
from peripheral chemoreceptors via CN IX and X
from mechanoreceptors in the lung via CN X
when do expiratory center become active?
during exercise when expiration becomes active
what are the consequence of hyperventilation?
decrease in PaCO2 -> arterial pH increase
central chemoreceptors are located in
brain stem
ventral surface of the medulla
near DRG
what do central chemoreceptors sense?
change in the pH of the cerebrospinal fluid
what will decrease in the CSF pH cause
hyperventilation
location of peripheral chemoreceptors?
- carotid bodies at the bifurcation of the common carotid arteries
- aortic bodies above and belowthe aortic arch
what do peripheral chemoreceptors sense?
O2
CO2
H+
what is the most important responsibility of the peripheral chemoreceptors?
detect changes in arterial PO2
peripheral chemoreceptors respond dramatically when
PO2 decreases to less than 60 mmHg
** so btw 60-100 mmHg nothing happens
What about decrease in arterial pH in relation to peripheral chemoreceptors?
mediated only by chemoreceptorsin the carotid bodies
Muscles of Inspiration?
Diaphragm
External intercosal
Scalenes
What is the Pneumotaxis center?
turns off inspiration
limits size of tidal volume
what reflex is initiated when the lungs stretch receptors are distended
Hering-Breuer reflex
to decrease breathing rate
