2017.10.17.

1

Respiratory physiology 3.

Control

Prof. Gyula Sáry

1

normoventilation

hypoventilation

hyperventilation

eupnoe

bradypnoe

tachypnoe

orthopnoe

dyspnoe

asphyxia

What do these terms mean?

2

2017.10.17.

2

1.

2.

3.

Reflexes and negative feedback

3

Rhytm generator

Respiratory muscles

Arterial blood, CSF

Chemoreceptors +

mechanoreceptors

in lung, muscle, joints

Alveolar

ventilation

Reference

value of

Changes in

metabolism,

inspired air,

circulation,

… 4

2017.10.17.

3

Respiratory drive

• A „simple” question: if metabolism in the body

produces CO2 (has to be removed) and

needs O2 (has to be supplied)

which one is more important in driving respiration?

– What experiment would you design?

5

A simple view

Chemoreceptors,

mechanoreceptors

-prolonged inspiration

-turns off inspiration

Cerebral cortex

(voluntary hyperventilation

and hypoventilation)

6

2017.10.17.

4

Respiratory centers in the brainstem

Central pattern generation(pre-Bötzinger)

Dorsal respiratory group (I)

Ventral respiratory group (I & E)

Chemoreceptors in arteries

& lung mechanoceptors

Pontine Respiratory Group :

Parabrachial nucleus & Kölliger- Fuse

(modulates, inhibits)

7

Ventilatory volumes and efferent nerve activity

inspiration

expiration

C3-C5

T1-T11

8

2017.10.17.

5

Respiratory rhytm

Neurogenic rhytm

Inspiration Expiration

Lung volume

Phrenic nerve (inspiratory)

Diaphragm constriction

Intercostal nerve (expiratory)

3 phases

I= inspiratory phase

PI= postinspiratory phase

E2= expiratory phase

9

Responses of the ventilation to:

arterial PO2;

arterial PCO2;

and blood pH.

10

2017.10.17.

6

Central chemoreceptors

Dorsal respiratory

group

11

Negative feedback in CO2 control

12

2017.10.17.

7

Arterial (peripheral) chemoreceptors

N. IX.

action pot.

Dopamin

receptor

Ca++ flowoutflow

13

Carotid body chemoreceptor responses

14

2017.10.17.

8

Carotid body chemoreceptor responses

PaO2 and PaCO2 have synergistic effect

pHa and PaCO2 effects

on carotid body receptors

pH acts only on the carotid body receptors!!

15

Test: re-breathing method

Effects originate from the

central receptors

Ventilatory responses to PACO2

(hypercapnic respiratory response)

16

2017.10.17.

9

CO2 narcose (CO2 in the air)

CO2 content in atmospheric air is very low (0.04%)

1% --> inreased respiratory rate

5% --> dyspnea

10% --> restlessness, dyzziness, headache

15% --> consciousness lost

20-30% --> CO2 narcose

cellar accidents at harvest time

17

Ventilatory responses to pHa

Only the

carotid bodies

react!(Kussmaul type)

18

2017.10.17.

10

Ventilatory response to PaO2

(hypoxic ventilatory response)

non-linear response

CO2 rulez!

19

Adaptation to CO2

• Long term increases in arterial PaCO2

• Sleeping pill poisoning

drive for respiration: O2 receptors

consequences of extra O2

20

2017.10.17.

11

Pulmonary (airway) reflexes

sneezing

sniffing, swallowing

expiratory relex, coughing

Hering-Breuer reflex

coughing, mucus,

bronchial constriction

rapid breathing, mucus

tachypnea, (embolism, edema)21

Cutting the vagal nerve...

22

2017.10.17.

12

Pathological resporatory patterns

acidosis (respiration compensates)

medullar and pontin lesion

severe disturbance, agony

sleep, high altitude, opiates

brainstem lesion, meningitis Biot

23

Explanation for the Cheyne-Stokes breathing

apnoe

24

2017.10.17.

13

Basic respiratory rhythm; a summary

25

Don’t hyperventillate before diving!

CO2 receptors stimulated too late

26