REGULATION OF RESPIRATION

REGULATION OF RESPIRATION

1. DR NILESH KATE
MBBS,MD
ASSOCIATE PROF
DEPT. OF PHYSIOLOGY
REGULATION
OF
RESPIRATION.

2. OBJECTIVES
Introduction.
Neural Regulation.
Automatic control.
Afferent impulses to respiratory centre.
Chemical regulation.
Chemoreceptors.
Effect of pO2, pCO2 & H+ ion conc on respiration.
Applied aspects.
Friday, June 17, 2016

3. INTRODUCTION.
The normal rate of respiration in
adults is 12-18/min,
Tidal volume of approx. 500 ml.
Adjusted to the requirements of
the body.
Spontaneous respiration -
rhythmic discharge of motor
neurons that innervate the
respiratory muscles.
Friday, June 17, 2016

4. CONTROL MECHANISMS.
Automatic control as
an involuntary
function.
Located in medullary
& pontine centres.
Functional
significance – breath
without conscious
effort as in sleep.
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5. CONTROL MECHANISMS.
Voluntary control.
Located in cerebral
cortex.
Functional
significance – facilitate
acts like talking, singing,
swimming, laughing,
breath holding &
hyperventilation.
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6. FUNCTIONS OF RESPIRATORY
CENTRES.
Genesis of normal
respiratory
spontaneous rhythm.
Control rate & depth
of respiration.
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7. REGULATION.
Neural
Automatic control.
Afferent impulses to respiratory centre.
Chemical.
Chemoreceptors
Effect of Po2, Pco2 &pH.
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8. AUTOMATIC CONTROL.
Medullary respiratory
centres.
Pontine respiratory
centre.
Reticular activating
system.
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9. MEDULLARY RESPIRATORY
CENTRES.
Dorsal respiratory
group of neurons.
Ventral respiratory
group of neurons.
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10. DORSAL RESPIRATORY GROUP OF
NEURONS..
NTS (Nucleus of Tractus
Solitarius)
I neurons – Discharge
during inspiration only.
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11. CENTRAL INSPIRATORY
ACTIVITY NEURONS.(RΑ)
Central inspiratory
activity neurons.(Rα)
Inspiratory pump.
Ramp signal.
Inspiratory off-switch
(IOS) neurons.
Terminate inspiratory
Ramp.
Integrator neurons. (Rβ)
Other neurons.(P cells)
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12. INTEGRATOR NEURONS. (RΒ)
Excitatory inputs.
Cerebral cortex.
Pneumotaxic
centre.
Vagal afferents
from stretch
receptors.
Inhibitory inputs.
Apneustic centre.
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13. VENTRAL RESPIRATORY GROUP
OF NEURONS.
Caudal part or nucleus
Retroambigualis
(NRA)
E neurons
Bulbospinal expiratory
Premotor neurons.
Intermediate part.
I neurons.
N. Parambigualis
Most Rostral part.(NRF)
Botzinger complex (E
neurons)
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14. VENTRAL RESPIRATORY GROUP
OF NEURONS.
Interactions of I & E
neurons.
Role of VRG neurons.
Totally inactive in
quiet breathing.
Active during forceful
respiration.
Example -- During
exercise
Reciprocal
innervations.
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15. PONTINE RESPIRATORY
CENTRE.
Apneustic Centre (APN)
Inhibitory neurons
bilaterally in pons.
APN – Integrator – IOS
Prevent switch off of ramp
from CIA
Increases depth & duration
– Apneusis.
Normally kept inhibited by
vagus & Pneumotaxic centre
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16. PONTINE RESPIRATORY
CENTRE.
Pneumotaxic centre.
(PNC)
In N. Parabrachialis in
upper pons.
Excite integrator N &
inhibits Apneustic C.
Increases rate of breathing.
So Rhythm by DRG, rate &
depth controlled by
APN,PNC.
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17. RETICULAR ACTIVATING
SYSTEM.
Increases respiratory
drive.
During sleep – RAS
activity decreases –
respiratory drive
decreases – alveolar
ventilation decreases
– raise Pco2.
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18. AFFERENT IMPULSES TO
RESPIRATORY CENTRE.
From higher centre.
From non-chemical receptors.
From chemical receptors.
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19. Friday, June 17, 2016

20. FROM HIGHER CENTRE.
Voluntary control
system.
Controlled by Neocortex
Bypasses medullary
respiratory centres &
project directly to spinal
respiratory neurons.
For talking, singing,
swimming & breath
holding.
Limbic control
system.
Limbic system –
pontomedullary
respiratory neurons.
So alter during pain &
emotional stimuli.
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21. FROM NON-CHEMICAL RECEPTORS.
From Pulmonary stretch receptors (Hering-
Breuer Reflex)
From J-Receptors.
From Irritant receptors in the respiratory tract.
From Proprioceptors..
From Chest wall stretch receptors.
From Baroceptors.
From Thermoceptors.
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22. Friday, June 17, 2016

23. FROM PULMONARY STRETCH RECEPTORS
(HERING-BREUER REFLEX)
Lung inflation –
stimulation of
stretch receptors in
bronchi & bronchioles
– vagi –
pontomedullary
respiratory centers –
inhibit respiration.
Only when TV > 1-1.5L
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25. Friday, June 17, 2016

26. FROM J-RECEPTORS.
Indian physiologist A.S
Paintal 1954.
Juxtapulmonary capillary
receptors. (unmyelinated
vagal afferents)
Sensitive to increase in
content of interstitial fluid
between capillary
endothelium & alveolar
epithelium.
Stimulation causes
apnoea,
hyperventilation,
bradycardia ,
hypotension &
weakness of skeletal
muscles.
Friday, June 17, 2016

27. FROM IRRITANT RECEPTORS IN
THE RESPIRATORY TRACT.
Cough reflex.
Sneezing reflex.
Hering-Breuer
deflation reflex.
Reflex tachypnoea &
bronchoconstriction.
Deglutition reflex.
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28. FROM PROPRIOCEPTORS.
Stimulate inspiratory neurons – increase rate &
depth of respiration.
Increases ventilation during exercise.
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29. FROM CHEST WALL STRETCH
RECEPTORS.
In muscle spindles of
intercostal muscles
Co-ordinate breathing
during change in posture
& during speech.
Intercostal to intercostal
reflex.
Intercostal to Phrenic
reflex.
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30. FROM BAROCEPTORS.
Raise BP – stimulate
Baroreceptors in
carotid sinus & aortic
arch.
Inhibition of
respiration.
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31. FROM THERMOCEPTORS.
2 types, warm & cold.
Warm receptors – via
somatic afferent
nerves – cerebral
cortex –
hyperventilation.
(Heat loss mechanism)
E.g. Panting in Dogs.
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32. FROM CHEMICAL RECEPTORS.
CHEMORECEPTORS.
Peripheral
Central.
Pulmonary & Myocardial.
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33. PERIPHERAL CHEMORECEPTORS.
Location - carotid bodies &
aortic bodies.
Structure.
Capsule – surrounding
bodies.
Sinusoidal large capillaries
below capsule
Epithelial cells – type I
(Glomus cells) like
chromaffin cells contains
catecholamine.
Type II (Glial cells).
Friday, June 17, 2016

34. PERIPHERAL CHEMORECEPTORS.
Mechanism
Less Po2 – decreases
activity of K channels –
decrease K efflux –
depolarization of glomus
cells – open L-type ca
channels – Ca influx –
release neurotransmitter
& stimulate afferent
nerve.
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35. FACTORS STIMULATING
O2 tension V o2
content.
Elevated Pco2
H+ conc.
Hyperkalemia.
Asphyxia.
Functions
Carotid bodies
increases both rate &
depth, aortic bodies
only rate of
respiration.
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36. CENTRAL CHEMORECEPTORS.
Location – beneath
ventral surface of
medulla.
Innervations –
project directly to
respiratory centres
deeper to central
chemoreceptors.
Mechanism.
Co2 crosses BBB – in
CSF
co2 + H2O – H2CO3
H2CO3 ------H+ HCO3
H+ ion stimulate
central
chemoreceptors.
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39. PULMONARY & MYOCARDIAL
CHEMORECEPTORS.
Location – pulmonary &
coronary blood vessels.
Innervations – by Vagus
(X) nerve.
Characteristics & effects.
Caused by injection of
veratridine or nicotine
Causes – bradycardia,
hypotension, apnoea
followed by tachypnoea.
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40. Friday, June 17, 2016

41. EFFECT OF PO2, PCO2 & H+ ION
CONC ON RESPIRATION.
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42. EFFECT OF HYPOXIA
Normal arterial Po2 is
100 mm Hg. Decrease
in Po2 causes Hypoxic
Hypoxia.
A decrease in arterial
Po2
Po2 100-60mm Hg. –
breaking effect of CO2.
Po2 below 60 mm Hg.
Friday, June 17, 2016

43. EFFECT OF HYPERCAPNIA.
Normal pco2 – 40 mm Hg.
Effect of Hypercapnia.
Co2 Narcosis when PCO2 >
50 mmHg.
Leads to depress CNS,
Respiratory centre,
headache, confusion,
convulsion, coma & Death.
Friday, June 17, 2016

44. EFFECT OF ARTERIAL pH
Increase H+ ion conc.
(metabolic acidosis)-
leads to
hyperventilation. In
DKA, renal failure,
severe exercise.
Decrease H+ ion conc.
(metabolic alkalosis)
Primary pulmonary
hypoventilation
causes respiratory
acidosis.
Primary pulmonary
Hyperventilation
causes respiratory
alkalosis.
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45. EFFECT OF HYPERVENTILATION.
Hypoventilation.
Apnoea.
Periodic breathing
(chynes-stokes
breathing)
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46. EFFECT OF SLEEP ON
RESPIRATION.
Apnoea for brief
period (10 sec)
Sleep apnoea
syndrome.
Friday, June 17, 2016

47. Thank
You