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Control of Ventilation

Explore the lectures on respiratory physiology focusing on the control system, including the medulla and pons in the brainstem, rhythm controllers, and the impact of other brain regions on respiration. Discover the sensors like chemoreceptors and lung receptors, as well as the critical ventilatory responses, such as the effect of CO2, PO2, and pH levels, including during exercise and at high altitudes.

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Control of Ventilation

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  1. Control of Ventilation Lectures on respiratory physiology

  2. Respiratory control system

  3. Diagram showing the pons and medulla oblongata

  4. Rhythm controllers in the brainstem • Medulla • Dorsal respiratory group – associated with inspiration • Ventralrespiratory group – associated with expiration. • Pre-Botzinger Complex - pattern generator, also ventral • 2) Pons Apneustic center – has an excitatory function • Pneumotaxic center – can inhibit inspiration

  5. Other regions of the brain that can affect respiration • Cortex • Can exercise voluntary control • 2)Limbic system and hypothalamus Emotional states

  6. Effectors • Diaphragm • Intercostal muscles • Abdominal muscles • 4) Accessory muscles

  7. Sensors • Central chemoreceptor • Peripheral chemoreceptors • Lung receptors • 4) Other receptors

  8. Chemoreceptors • Specialized tissues that responds to a change in the chemical composition of the blood or other fluid • Central chemoreceptor • Peripheral chemoreceptors

  9. Central chemoreceptor

  10. Central chemoreceptor • Responds to pH of ECF • CO2 diffuses across the blood-brain barrier • Normal CSF pH is 7.32 • CSF has little buffering • CSF bicarbonate controlled by choroid plexus

  11. Sites of peripheral chemoreceptors

  12. Carotid body receptor and its response

  13. Carotid bodies • Respond to PO2, PCO2 and pH • Little response in normoxia • Very high blood flow • Respond to arterial, not venous PO2 • Fast response

  14. Lung receptors • Pulmonary stretch receptors (also called slowly-adapting pulmonary stretch receptors) Responsible for the Hering-Breuer reflex • Irritant receptors (also called rapidly-adapting pulmonary stretch receptors) • J receptors (juxta-capillary receptors) • 4) Bronchial C fibers

  15. Other receptors • Nose and upper airway • Joint and muscle • Gamma system • Arterial baroreceptors • Pain and temperature

  16. Integrated responses • Response to increased PCO2 • Response to reduced PO2 • Response to changes in pH • 4) Response to exercise

  17. Ventilatory response to CO2

  18. Response to CO2 • Primary factor in the control of ventilation • Measured by rebreathing from a bag • Inspiratory pressure following brief occlusion • Response is altered by sleep, age, genetic factors • Reduced by increasing the work of breathing

  19. Ventilatory response to PO2

  20. Response to reduced PO2 • No role under normoxic conditions • Measured by rebreathing from a bag • Increased response if the PCO2 is raised • Important at high altitude • Important in some patients with chronic lung disease

  21. Response to reduced pH • Sensed by the peripheral chemoreceptors • Important in metabolic acidosis • If the reduction is severe, central chemoreceptors may be stimulated

  22. Response to exercise • Blood gases are normal • pH is normal except at heavy exercise • ? Cortex, impulses from limbs, increased temperature, resetting of CO2 reference level

  23. Sleep apnea • Obstructive: very common; often associated with obesity; sleep deprivation may cause daytime somnolence and impaired cognitive function • Central: respiratory depression during sleep; recognized by the absence of respiratory efforts

  24. Periodic Breathing at High Altitude

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