1. Chapter 18b Gas Exchange and Transport

2. 15 16 Expiration Inspiration Sensory receptors Integrating centers Efferent neurons Effectors Afferent neurons Stimuli KEY Afferent sensory neurons Carotid and aortic chemoreceptors External intercostals Internal intercostals Abdominal muscles Diaphragm Somatic motor neurons (inspiration) Somatic motor neurons (expiration) Medullary chemoreceptors Emotions and voluntary control Medulla oblongata and pons Scalene and sternocleidomastoid muscles CO 2 O 2 and pH Limbic system Higher brain centers 13 14 1 2 3 4 5 6 12 11 10 7 8 9 Reflex Control of Ventilation Figure 18-16

3. PRG PRG = Pontine respiratory group DRG VRG Output to expiratory, some inspiratory, pharynx, larynx, and tongue muscles Output primarily to inspiratory muscles Sensory input from CN IX, X (mechanical and chemosensory) Medullary chemo- receptors Higher brain centers NTS pre-Bötzinger complex Pons Medulla KEY DRG = Dorsal respiratory group VRG = Ventral respiratory group NTS = Nucleus tractus solitarius Regulation of Ventilation 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 pons modulate ventilation Ventilation is subject to modulation by chemoreceptor-linked reflexes and by higher brain centers Apneustic and 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 P O 2, pH, and P CO 2 central chemoreceptors Changes in CO 2

8. Regulation of Ventilation Carotid body oxygen sensor releases neurotransmitter when P O 2 decreases Figure 18-19 7 6 5 4 3 2 1 K + channels close Low P O 2 Blood vessel Voltage-gated Ca 2+ channel opens Ca 2+ entry Cell depolarizes Exocytosis of neurotransmitters Receptor on sensory neuron Glomus cell in carotid body Signal to medullary centers to increase ventilation Action potential Low P O 2

9. H+H+ CO 2 + H 2 O Cerebral capillary Blood-brain barrier Cerebrospinal fluid Medulla Central chemoreceptor P CO 2 Respiratory control centers Ventilation CA H 2 CO 3 H + + HCO 3 – Regulation of Ventilation Central chemoreceptors monitor CO 2 in cerebrospinal fluid Figure 18-20

10. Regulation of Ventilation Chemoreceptor response to changes in plasma CO 2 Figure 18-21 Plasma P O 2 Stimulates central chemoreceptor P CO 2 in CSF Arterial P CO 2 in plasma Plasma P CO 2 Stimulates peripheral chemoreceptor Plasma P O 2 < 60 mm Hg Ventilation CO 2 in CSF HCO 3 – H + + HCO 3 – CO 2 H + + Plasma P CO 2 Negative feedback

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