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Control of Ventilation

Control of Ventilation. Lectures on respiratory physiology. Respiratory control system. Diagram showing the pons and medulla oblongata. Rhythm controllers in the brainstem. Medulla Dorsal respiratory group – associated with inspiration Ventral respiratory group – associated with expiration.

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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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