Neural regulation of_respiration

IT INCLUDES ALL THE RESPIRATORY CENTER IDENTIFIED TILL NOW AND THEIR MODULATION VIA DIFFERENT FACTORS. OVERALL IT EMPHASIS ON HOW CNS CAN ALTER THE FREQUENCY OF RESPIRATION

1. NEURAL CONTROL OF RESPIRATION DEPARTMENT OF PHYSIOLOGY SCHOOL OF MEDICAL SCIENCES AND RESEARCH SHARDA UNIVERSITY NAME:SANJOG BAM Msc IIIrd year

2. Learning objectives Voluntary control Centres of automatic control Medullary respiratory centre Central pattern generator Pontine respiratory centre Hering -Breuer reflex Factors affecting the respiratory centre

3. Neural control of respiration Two separate neural control mechanism: Voluntary control Automatic control Voluntary control : Centres are located in the cerebral cortex Controls respiratory muscles via cortico spinal tract By pass brainstem Limitation: breaking point ,where automatic control over ride

4. Automatic control: Centres are located in brain stem Respiratory centres are divided into three major collections of neurons: Dorsal respiratory group Ventral respiratory group Pneumotaxic centre Apart from that other centre also lies, they are Central pattern generator Apneustic centre

5. Transection of brain stem at different levels: Dorsal view

6. Ventral respiratory group - Located in the ventrolateral medulla -Consist both inspiratory and expiratory neuron -These group of neurons are found in NA rostrally and nucleus retroambigualis caudally Neurons in the VRG are almost inactive during the quiet respiration. The VRG area contribute to extra respiratory drive during increased pulmonary ventilation. Consists B otzinger complex, rostral inspiratory region and caudal expiratory region

7. Cross communication between the centres of both sides help them to work synchronously and harmoniously, causing simultaneously and symmetrically movements of both sides of chest.

8. Central pattern generator Present in the pre- Botzinger complex Synaptically coupled pacemaker cells located bilaterally between NA and lateral reticular nucleus Responsible for generating normal respiratory rhythm. Rhythmic discharge in the phrenic nerve . CPG is also influenced by the integrator Integrator controls mainly the frequency and amplitude of respiratory pattern

9. Close contact with hypoglossal nuclei Nk 1 and µ-opioid receptor are present now also 5-HT 4 receptor are found

10. Pontine respiratory centre Pneumotaxic and apneustic centre Modulate output from medullary centre Pneumotaxic centre: Located in nucleus parabrachialis medialis and kolliker fuse nuclei dorsolateral in rostral pons May coordinates respiration by switching between inspiration and expiration Some neurons active during inspiration and some during expiration. Limits duration of inspiration and increases the rate. Pneumotaxic centre inhibits apneustic centre.

11. Apneustic centre Present in caudal pons Apneustic centre strongly activates medullary inspiratory centre This centre is tonically inhibited by pneumotaxic centre

12. Hering -Breuer Reflex Described by Hering and breuer in 1868 Volume reflex and operates due to inflation and deflation Safety mechanism Stimulates slow adapting receptor which inhibits inspiration and prolongs expiration. Stimulate the inspiratory off-switch. Important in adults during exercise and in infants controls tidal volume during eupnea

13. Factors affecting respiratory centre Impulse from higher centre Impulse from stretch receptor Impulse from J receptor Irritant receptors of lungs Impulse from proprioreceptor Thermoreceptor Pain receptor

14. Ondine curse: Impairment of automatic respiratory control Needs volitional breathing for survival If preventive measures is not taken the person can die any time in sleep Stroke can cause destruction of voluntary control over respiration.

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