midbrain

9. Respiratory center summary midbrain (upper pons) – inhibits inspiration pneumotaxic center pons Apneustic center (lower pons) – to promote inspiration medulla Cause the basic respirarory rhythm transfer for brain and respiratory muscle Spinal cord hypothesis of three –lever of respiratory center

10. PBKF neurons

11. dorsal respiratory group ventral respiratory group

12. Two respiratory nuclei in medulla oblongata • Inspiratory center (dorsal respiratory group, DRG) • inspiratory neuron • more frequently they fire, more deeply you • inhale，longer duration they fire, breath is • prolonged, slow rate • Expiratory center (ventral respiratory group, VRG) • expiratory neuron, inspiratory neuron involved in forced expiration mainly

13. pond PBKF neurons dorsal respiratory group ventral respiratory group Spinal cord

14. hypothesis of basic rhythm——pacesetter cell theory pneumotaxic center PBKF neurons Central inspiratory activity generator inspiratory nueron Inspiratory off swithch mechanism Inspiratory muscle motor nueron

15. Rhythmic Ventilation (Inspiratory Off Switch) • Starting inspiration • Medullary respiratory center neurons are continuously active (spontaneous) • Center receives stimulation from receptors and brain concerned with voluntary respiratory movements and emotion • Combined input from all sources causes action potentials to stimulate respiratory muscles

16. Increasing inspiration • More and more neurons are activated • Stopping inspiration • Neurons receive input from pontine group and stretch receptors in lungs. • Inhibitory neurons activated and relaxation of respiratory muscles results in expiration. • Inspiratory off swithch.

17. 3. Higher Respiratory Centers regulate the activity of the more primitive control centers in the medulla and pons. Allow the rate and depth of respiration to be controlled voluntarily. During speaking, laughing, crying, eating, defecating, coughing, and sneezing. ….

19. deflation

20. Hering-Breuer Reflex or Pulmonary Stretch Reflex • Including pulmonary inflation reflex and pulmonary deflation reflex • Receptor: Slowly adapting stretch receptors (SARs) in bronchial airways. • Afferent: vagus nerve

22. Significance of Hering-Breuer reflex • Terminate inspiration timely. • enhance inspiration/expiration transition，increase respiratory frequency. • Normal adults. Receptors are not activated at end normal tidal volumes. • Become Important in Chronic obstructive lung diseases when lungs are more distended. • Infants. Probably help terminate normal inspiration. • Become Important during exercise when tidal volume is increased.

25. Chemoreceptor Reflex Two Kinds of Chemoreceptors • Central Chemoreceptors • Responsive to increased H+in CSF(cerebrospinal fluid) or local extracellular fluid • Peripheral Chemoreceptors • Responsive to decreased arterial PO2 • Responsive to increased arterial PCO2 • Responsive to increased H+ ion concentration.

26. Peripheral Chemoreceptors R：Carotid bodies • Aortic bodies adequate stimulus:PO2 PCO2 H+ exciting of breath depth and frequency Of breath pulmonary ventilation • glossopharyngeal nerve. • vagus

27. Carbon Dioxide, Oxygen and pH Influence Ventilation (through peripheral receptor) • Peripheral chemoreceptors sensitive to PO2, PCO2 and pH • Receptors are activated by increase in PCO2 or decrease in PO2 and pH • Send APs through sensory neurons to the brain • Sensory info is integrated within the medulla • Respiratory centers respond by sending efferent signals through somatic motor neurons to the skeletal muscles • Ventilation is increased (decreased)

28. Central Chemoreceptor Location Rostral Medulla Caudal Medulla Ventral Surface of the medulla

29. The sensor neurons are especially excited by H+ H+ are the only direct stimulus for these sensor neurons .

31. Carbon Dioxide • Indirect effects • through pH as seen previously • Direct effects • CO2 may directly stimulate peripheral chemoreceptors and trigger  ventilation more quickly than central chemoreceptors • If the PCO2 is too high, the respiratory center will be inhibited.

32. CO2 easily crosses blood-brain barrier • , in CSF the CO2 reacts with water and releases H+, • central chemoreceptors strongly stimulate inspiratory center arterial Blood –brain barrier Central Chemoreceptor Carbonic anhydrase

33. arterial peripheral Chemoreceptor Central Chemoreceptor

34. arterial peripheral Chemoreceptor Central Chemoreceptor

35. arterial peripheral Chemoreceptor Central Chemoreceptor 80% 20%

38. Effects of Hydrogen Ions Increasing H+ or decreasing PH can faster respiration. It is the effective stimulator to chemoreceptor. Pathway of H+ regulating respiration a. H+ in blood increases—excites peripheral chemoreceptor mainly b. H+ in cerebrospinal Fluid increases-- excites central chemoreceptor

44. Oxygen character 1)Hypoxia stimulation act through peripheral chemoreceptor. If the inputing of peripheral chemoreceptor is cut, the stimulation effect disappear. 2)The direct effect of hypoxia to center is inhibition. 3)hypoxia ：PO2< 80mmHg ventilation volume increase is been awareness.

45. The pathway of hypoxia regulating respiration: • The main pathway is acting directly on peripheral chemoreceptor and inputting impulse. Respiration center is excited. • Chronic hypoxemia, PO2 < 60 mmHg, can significantly stimulate ventilation • emphysema, pneumonia • high altitudes after several days

46. Brief summary Central Chemoreceptor peripheral Chemoreceptor

49. Overall Response toPco2, Po2 and pH