Lecture 25 Respiratory 2 Flashcards Preview

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Flashcards in Lecture 25 Respiratory 2 Deck (22)
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1

Gas exchange

gas exchange in the lungs occurs by diffusion across the respiratory membrane

2

Partial pressure

(PO2, PCO2) is the driving force for diffusion of gases
gases diffuse down a partial pressure gradient (from high to low partial pressure)

3

Dalton's Law

total pressure = sum of partial pressure of gases in a mixture
Ptotal = PN2+PO2 + PCO2+PH2O

4

Ptotal

is atmospheric pressure = 760 mm Hg at sea level (lower at high altitude)
PO2= Ptotal X (%O2/100) = 760 X.021 = 160 mm Hg

5

Partial pressure

+ total pressure X fractional concentration of gas (%100)

6

How does O2 diffuse

O2 diffuses from air in alveoli to blood in pulmonary capillaries

7

How does CO2 diffuse

CO2 diffuses from pulmonary capillaries into alveoli

8

High diffusion efficiency due to

1. high surface area of alveoli
2. thin respiratory membrane

9

Inspired air PO2 and PCO2

PO2 = 160
PCO2 = 0.3

10

Alveolar air PO2 and PCO2

PO2 = 100
PCO2 = 40

11

Pulmonary veins and systemic arteries PO2 and PCO2 and saturation

PO2 = 100
PCO2 = 40
O2 saturation = 98% (arterial blood)

12

Vena Cava and Pulmonary arteries PO2 and PCO2 and O2 saturation

PO2= 40
PCO2= 46
saturation = 75% (mixed venous blood)

13

Pulmonary gases and diffusion

blood PO2 and PCO2 in pulmonary capillaries normally reach equilibrium with alveolar air
ventilation and pulmonary blood flow maintain PO2 and PCO2 gradients between air and blood

14

Respiratory centers control breathing

primary respiratory control regions located in brainstem
controls inspiratory neurons and expiratory (E) neurons
medulla oblongata
pons

15

Medulla oblongata

central pattern generator generates breathing rhythm
dorsal respiratory group (mostly I neurons)
ventral respiratory group (E and I neurons)

16

Pons

pontine respiratory group, functions to smooth out breathing rhythm

17

Chemoreceptors

central chemoreceptor in medulla oblongata
peripheral chemoreceptors in carotid bodies

18

Central chemoreceptors

sensitive to PCO2 via increase [H+] (decrease pH) of cerebrospinal fluid (CSF)
increase arterial PCO2 -> increase PCO2 of CSF
CO2 + H20 -> H2CO3 -> H+ + HCO3-
increase [H+] in CSF -> stimulates increase ventilation

*central chemoreceptor has the dominant role in regulating breathing at rest

19

Peripheral chemoreceptors

sensitive to low PO2 also PCO2 and pH of arterial blood
stimulate ventilation directly at very low PO2 (<60 mm Hg)
increase sensitivity of central response to CO2
contribute to increase in ventilation during exercise

20

Ventilation

is normally regulated to maintain constant arterial PCO2 (normal = 40 mm Hg)

21

Hypoventilation

increase PCO2 (>45 mm Hg)

22

Hyperventilation

decrease PCO2 (<35 mm Hg)