This presentation gives a detailed description of the physiology of Neural Regulation of Respiration in Human. The role played by the Medullary and Pontine Centers in respiration is highlighted. A detailed diagram and the reflexes involved in controlling Respiration are described for the understanding of the student. Standard reference books have been used to describe the topic.

1. NEURAL REGULATION OF
RESPIRATION
DR ELIZABETH JOSEPH
PROFESSOR OF PHYSIOLOGY

2. SCHEME
• TYPES OF RESPIRATION
• INNERVATION OF RESPIRATORY SYSTEM
• MEDULLARY CENTRES
• PONTINE CENTRES
• INSPIRATORY SIGNAL
• INSPIRATORY ‘OFF SWITCH’
• OTHER NEURAL SIGNALS CONTROLLING
RESPIRATION

3. TYPES OF RESPIRATION
I SPONTANEOUS OR AUTOMATIC –
CONTROL BY NEURON GROUPS IN MEDULLA & PONS
II VOLUNTARY CONTROL BY HIGHER CENTRES-
- UNDER THE CONTROL OF CEREBRAL CORTEX
(by passes the medullary & pontine centres)
- LIMBIC CONTROL SYSTEMS (emotional & painful stimuli)
IMPULSES FROM NON CHEMICAL RECEPTORS
(stretch, pulmonary congestion, irritant & proprioceptors)

4. INNERVATION OF RESPIRATORY SYSTEM
RECIPROCAL
INNERVATION:
Motor neurons to
expiratory neurons
are inhibited when
inspiratory neurons
are active & vice versa.
INSPIRATORY NEURONS
EXPIRATORY NEURONS
- VE -VE

5. CONTROL OF RESPIRATION

6. DIAGRAM OF RESPIRATORY CENTRES
Pneumotaxic centre
4 th Ventricle
? Apneustic centre
Dorsal respiratory group
Ventral Respiratory group

7. MEDULLARY CENTRES
DORSAL RESPIRATORY GROUP (DRG)
Location:
Bilaterally mostly in Nucleus Tractus Solitarius( NTS) &
lesser in Reticular system. Afferents of X th & IX th nerve
RHYTHMIC DISCHARGE:
Repititive burst’s of inspriratory neuronal potentials
Signals relayed from - Peripheral chemoreceptors
- Baroreceptors
- Other Lung receptors

8. INSPIRATORY “RAMP” SIGNAL
RATE OF INCREASE OF “RAMP” SIGNAL
Signal to diaphragm is not an instantaneous burst
Steady increase in action potential forming a ramp
2 qualities of the “RAMP”
-RATE OF INCREASE OF “RAMP” SIGNAL
- LIMITING POINT OF THE “RAMP”
earlier ramp ceases – Frequency of respiration

9. PONTINE CENTRES
PNEUMOTAXIC CENTRE
Dorsal in Nucleus
Parabrachialis of upper pons.
Functions
LIMITS INSPIRATION
Increases rate of Respiration
“ INSPIRATORY OFF SWITCH”
(IOS)
? APNEUSTIC CENTRE
Lower pons
Functions
Inhibits the IOS
Results in deeper prolonged
inspiration “APNEUSIS”
Seen in lower animals

10. INSPIRATORY “OFF” SWITCH
Pneumotaxic centre
Strong signals – 0.5 sec inspiratory phase
30-40 respiratory rate
Weak signals – 5 secs or more inspiratory phase
3-5 respiratory rate
Respiratory cycle shortens

11. VENTRAL RESPIRATORY GROUP
5 mm anterolateral to the DRG rostrally in nucleus
Ambiguus & nucleus Retroambiguus.
Functions:
- Inactive in normal respiration
- Signals spill over from DRG during increase in
pulmonary ventilation
- Expiratory neurons active during heavy respiration

12. CONCEPT OF RESPIRATION

13. OTHER INFLUENCES ON RESPIRATORY CENTRES
I HERING-BREUER INFLATION REFLEX:
Stretch Receptors Vagi DRG
Feedback signal (Like Pneumotaxic centre)
‘SWITCH OFF’ Respiratory rate
Tidal Volume must be thrice the normal for this reflex to work
II HERING BREUER DEFLATION REFLEX

14. OTHER NEURAL SIGNALS CONTROLLING
RESPIRATION
Higher centres – Cortex to respiratory neurons via
corticospinal tract. “Ondine’s curse.”
Limbic System- Emotion influencing respiration.
J receptors – Congestion in lung leading to dyspnoea.
Irritant Receptors – Coughing, sneezing leading to
hyperpnoea and dyspnoea.

15. OTHER NEURAL SIGNALS CONTROLLING
RESPIRATION
• Proprioceptors
Influences the level and timing of respiratory activity.
• Chest wall stretch receptors
Tendon organs of the muscles have an inhibiting
effect on inspiration.
• Baroceptors
Increased BP reflexly inhibits respiration
• Thermoreceptors
Increased temperature increases respiration.

16. REFERENCES
• GUYTON & HALL, TEXTBOOK OF MEDICAL
PHYSIOLOGY
• GANONG’S, REVIEW OF MEDICAL
PHYSIOLOGY