1. Neural regulation
D.A. Asir John Samuel, BSc (Psy), MPT (Neuro Paed),
MAc, DYScEd, C/BLS, FAGE
Lecturer, Alva’s college of Physiotherapy,
Moodbidri
Dr.Asir John Samuel (PT)

2. Respiratory center
• Group of neurons located bilaterally in
medulla oblongata and pons
• Dorsal respiratory group – inspiration
• Ventral respiratory group – ins/exp
• Pneumotaxic center, located dorsally in
superior portion of pons, rate and pattern
Dr.Asir John Samuel (PT)

3. Dr.Asir John Samuel (PT)

4. Respiratory center
Dr.Asir John Samuel (PT)

5. Chemical control
• Ultimate goal is to maintain proper
concentrations of oxygen, carbon dioxide and
hydrogen ions in tissues
• Excess CO2 or H+ in blood act on respiratory
center
Dr.Asir John Samuel (PT)

6. Chemical control
• Causes increased strength of both inspiratory
and expiratory motor signals to respiratory
muscles
• O2 does not have significant direct effect on
respiratory center
• Acts on peripheral chemoreceptors located in
carotid and aortic bodies
Dr.Asir John Samuel (PT)

7. Dr.Asir John Samuel (PT)

8. Direct chemical control
• A sensitive chemosensitive area, located B/L
lying 1/5th mm beneath ventral surface of
medulla
• Highly sensitive to changes in either blood
PCO2 or H+ concentration
• In turn excites the other portion of respiratory
center Dr.Asir John Samuel (PT)

9. H+ - the primary stimulus
• Sensor neurons in chemosensitive area are
especially excited by H+
• Direct stimulation
• Does not cross BBB
• Less effect in stimulating than do changes in
blood CO2
Dr.Asir John Samuel (PT)

10. Effect of blood CO2
• Little direct and indirect effect in stimulating
• Cross BBB
• When blood PCO2 increases, PCO2 of CSF and
interstitial fluid of medulla increases
• Immediately reacts with water
• Dissociates into carbonic acid and H+
Dr.Asir John Samuel (PT)

11. Dr.Asir John Samuel (PT)

12. Chemical control
CO2 crosses BBB
Increase Blood PCO2,increases PCO2 of CSF and
interstitial fluid of Medulla
Immediately reacts with H2O
H2CO3
Dissociates into H+ + HCO3_
Dr.Asir John Samuel (PT)

13. Peripheral chemoreceptor system
• Detects changes in O2 in blood
• Responds lesser to changes in CO2 and H+
• Carotid bodies and aortic bodies
• Some in thoracic and abdominal regions
Dr.Asir John Samuel (PT)

14. Peripheral chemoreceptors
• Carotid bodies are located B/L in bifurcations of
common carotid arteries
• Afferent nerve, Hering’s nerves to IX and X
• DRG of neurons in medulla
• Aortic bodies are located along the arch of aorta
• Afferent nerve fiber passes through X
Dr.Asir John Samuel (PT)

15. Stimulation peripheral chemoreceptors
• Richly vascularised
• 20 times weight of bodies
• Removal of O2 is virtually 0
• All times exposed to arterial blood
• Glomus cell, glandular cell
• PO2 changes from 60 down to 30 mm Hg
• Increases respiratory activity
• 5 times than central
Dr.Asir John Samuel (PT)