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Chapter 18b

Chapter 18b. Gas Exchange and Transport. Reflex Control of Ventilation. KEY. Emotions and voluntary control. 16. CO 2. O 2 and pH. Stimuli. Sensory receptors . 15. 1. Afferent neurons . 2. Higher brain centers. 14. Medullary chemoreceptors. Carotid and aortic chemoreceptors.

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Chapter 18b

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  1. Chapter 18b Gas Exchange and Transport

  2. Reflex Control of Ventilation KEY Emotionsand voluntarycontrol 16 CO2 O2 and pH Stimuli Sensoryreceptors 15 1 Afferentneurons 2 Higherbraincenters 14 Medullarychemoreceptors Carotid and aorticchemoreceptors Integratingcenters 13 3 Efferentneurons 4 Effectors 12 Limbicsystem Afferent sensoryneurons 5 6 7 8 Medulla oblongataand pons 11 10 Somaticmotor neurons(inspiration) Somaticmotor neurons(expiration) 9 Inspiration Expiration Externalintercostals Abdominalmuscles Internalintercostals Scalene andsternocleidomastoidmuscles Diaphragm Figure 18-16

  3. Regulation of Ventilation KEY PRG = Pontine respiratory group DRG = Dorsal respiratory group VRG = Ventral respiratory group NTS = Nucleus tractus solitarius Higherbraincenters Pons PRG NTS Medullarychemo-receptors Sensory inputfrom CN IX, X(mechanical andchemosensory) DRG Medulla pre-Bötzingercomplex VRG Output to expiratory,some inspiratory,pharynx, larynx, andtongue muscles Outputprimarily toinspiratorymuscles Figure 18-17

  4. Regulation of Ventilation • Respiratory neurons in the medulla control inspiration and expiration • Rhythmicity center Inspiration and Expiration • VRG and DRG of medulla • Rhythmic pattern of breathing arises from a network of spontaneously discharging neurons Neurons in the ponsmodulate ventilation • Ventilation is subject to modulation by chemoreceptor-linked reflexes and by higher brain centers • Apneusticand Pneumotaxic • Apenustic – inspiration • Pneumotaxic – anatagonistic – inhibit inspiration

  5. Rhythmicity of breathing

  6. Regulation of Ventilation • Neural activity cycles during quiet breathing Figure 18-18

  7. Regulation of Ventilation • Peripheral chemoreceptors • Located in carotid and aortic arteries • Specialized glomus cells • Sense changes in PO2, pH, and PCO2 central chemoreceptors • Changes in CO2

  8. Regulation of Ventilation Blood vessel Low PO2 • Carotid body oxygen sensor releases neurotransmitter when PO2 decreases 1 Low PO2 2 K+ channels close Celldepolarizes 3 Glomus cellin carotidbody Ca2+entry 5 4 Voltage-gated Ca2+channel opens 6 Exocytosis ofneurotransmitters Receptor onsensory neuron Action potential Signal to medullarycenters to increaseventilation 7 Figure 18-19

  9. Regulation of Ventilation Cerebral capillary • Central chemoreceptorsmonitor CO2 in cerebrospinal fluid Blood-brainbarrier H+ PCO2 CO2 + H2O H2CO3 H+ + HCO3– CA Cerebrospinalfluid Central chemoreceptor Medulla Respiratorycontrolcenters Ventilation Figure 18-20

  10. Regulation of Ventilation • Chemoreceptor response to changes in plasma CO2 PlasmaPCO2 PCO2 in CSF Arterial PCO2 CO2inCSF H+ + HCO3– CO2 H+ + HCO3– inplasma Stimulatescentralchemoreceptor Stimulatesperipheralchemoreceptor Plasma PO2< 60 mm Hg Ventilation Plasma PO2 Negative feedback Plasma PCO2 Figure 18-21

  11. Control of Ventilation PLAY Interactive Physiology® Animation: Respiratory System: Control of Respiration

  12. Regulation of Ventilation • Protective reflexes • Irritant receptors • Bronchoconstriction • Sneezing • Coughing • Hering-Breuer inflation reflex • Don’t over stretch and damage

  13. Summary • Diffusion and solubility of gases • Gas exchange • Gas transport • Transport of oxygen and carbon dioxide • Factors affecting oxygen-hemoglobin binding • Carbonic anhydrase and chloride shift

  14. Summary • Regulation of ventilation • Central pattern generator • Dorsal versus ventral respiratory groups • Peripheral versus central chemoreceptors

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