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Control of Respiration Week 4

Control of Respiration Week 4. Dr. Walid Daoud A. Professor. Respiratory Center (RC). Respiratory center is composed of a collection of neurons located bilaterally in pons and medulla. These neurons are either:

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Control of Respiration Week 4

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  1. Control of RespirationWeek 4 Dr. Walid Daoud A. Professor

  2. Respiratory Center (RC) Respiratory center is composed of a collection of neurons located bilaterally in pons and medulla. These neurons are either: - Inspiratory (discharge during inspiration) or - Expiratory (discharge during expiration). Inspiratory neurons are inhibited during expiratio and expiratory neurons are inhibited during inspiration.

  3. Medullary Respiratory Centers 1- Dorsal Respiratory Group (DRG) . In dorsomedial position in medulla. . Located bilaterally in nucleus tractus solitarius which is sensory termination of vagus and glossopharyngeal nerve and receive sensory information from mechanoreceptors, baroreceptors and chemoreceptors in the body

  4. Medullary Respiratory Centers 1- Dorsal Respiratory Group (DRG) - Inspiratory neurons having inherent rhythmicity with spontaneous depolarization. - Responsible for inspiratory activity. - DRG sends afferent impulses to: Inspiratory muscles and VRG. - DRG receives: Excitatory impulses from apneustic center. Inhibitory impulses from lung stretch receptors

  5. Medullary Respiratory Centers 2- Ventral Respiratory Group (DRG) . Lies ventrolateral to DRG. . Composed of both inspiratory and expiratory neurons as they contribute to both forced inspiration & expiration during hyperventilation . Remains inactive during quiet breathing i.e, no rhythm.

  6. Pontine Respiratory Centers They modify and regulate the function of the medullary centers. 1- Apneustic Center (APC): . In lower pons. . Responsible for SWITCH ON point of inspiration . It stimulates pneumotaxic center.

  7. Pontine Respiratory Centers 1- Apneustic Center (APC): . It receives inhibitory impulses from: - Lung stretch receptors. - Pneumotaxic center (PNC). . When APC is inhibited , inspiration will stop which will turn off the excitation of inspiratory muscles and allow el;astic recoil of the lung to cause expiration.

  8. Pontine Respiratory Centers 2 - Pneumotaxic Center (PNC): . PNC lies in upper pons. . It controls SWITCH OFF point of inspiration by sending inhibitory impulse to APC. . PNC by switching off inspiration will limit the duration of inspiration.

  9. Role of Vagus Nerve Hering-Breuer reflex: Stretch of the lungs stimulate stretch receptors in the lungs which will send impulses through vagi to APC and DRG. This will adjust the rate and depth of respiration at tidal volume 500 ml. The reflex is active in animals and newborn children. In adult human only during exercise.

  10. Genesis of Rhythmic Respiration -APC sends continuous regular discharge of signals exciting inspiratory neurons of DRG . -DRG sends impulses down the spinal cord to diasphragm and external intercostal muscles causing inspiration and stimulation of stretch receptors in the lungs which will inhibit APC and DRG via vagus. At the same time , PNC inhibits APC to switch off inspiration. -This stops inspiration and brings expiration

  11. Regulation of Respiration Regulation of respiratory center activity: I- Chemical regulation: Effects of variation of blood O2, CO2 , H ions on ventilation via chemoreceptors. It is basic mechanism for regulation of resp. II-Non-chemical (nervous) regulation: It is superimposed on the basic chemical regulation of respiration in particular situations.

  12. Chemical Regulation of Respiration It is the basic mechanism for regulation of breathing. -Increase arterial PCO2 -Increase arterial H ion -Decrease arterial PO2 Stimulate respiratory chemoreceptors Increase activity of respiratory center and Increase pulmonary ventilation.

  13. Central Chemoreceptors Site: Located bilaterally just beneath central surface of medulla. Stimulus: 1- Response to H ion ( primary stimulus). 2- Response to PCO2. 3- Response to Po2.

  14. ChemoreceptorsPeripheral Site: Aortic bodies: over aortic arch Carotid bodies: at bifurcation of each common carotid artery. Innervation: Carotid bodies: glossopharyngeal nerve Aortic bodies: vagus nerve

  15. Mechanism of stimulation of peripheral chemoreceptors 1- Oxygen tension. 2- H ion concentration. 3- CO2 tension

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