Respiratory 2 Flashcards by shir nov

4 laws

Boyles
Daltons
Henrys
Ficks

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Boyles law

P1V1=P2V2

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Daltons law

Partial P of gas is the P that gas would exert if it occupied the entire volume of the mixture

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Partial pressure of O2

159 mmHg

21% of 760 mmHg

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Henrys law

Pp liquid = Pp gas

If alveolar PO2=100 mmHg, also arterial PO2=100 mmHg

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Ficks law

Transfer of gas across membrane is due to simple diffusion

Driven by difference in partial pressure

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Which gas diffuses faster?

O2
CO2

CO2

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Forms of gases in the blood

Free
Bound
Chemically modified

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Which gas is never bound/chemically modified?

Nitrogen

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Give example of chemically modified gas?

CO2 into bicarbonate

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Inspired air gas composition

O2= 158 mmHg
CO2= 0.3 mmHg
H2O= 5.7 mmHg
N2= 596 mmHg

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Right heart gas composition

O2= 40 mmHg
CO2= 46 mmHg

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Left hear gas composition

O2= 95 mmHg
CO2= 40 mmHg

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Expired air gas composition

O2= 116 mmHg
CO2= 32 mmHg

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Gas flow can be limited by two things

Diffusion limited

Perfusion limited

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Pulmonary blood flow=

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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