School of Medicine SUNYAB PGY452 Respiratory Lectures March 31 2015 Daniel D Swartz Ph D Lecture 7 Control of Respiration Reading Assignment Berne Levy chapter 24 pages 468 476 Control of Ventilation Central Nervous System Somatic motor neurons Rhythmic Ventilation Central Pattern Generator Chemoreceptor Reflexes Cardiovascular Control Centers Emotions Conscious and Unconscious Control Modulators Chemoreceptors Chemoreceptors CO2 O2 H present in extracellular fluid Peripheral chemoreceptors plasma in the carotid and aortic bodies most responsive to Po2 Glomus cells activated by decrease in Po2 or pH or an increase in Pco2 result in increased ventilation Central chemoreceptors respond to CO2 in cerebral spinal fluid on ventral surface of medulla most responsive to Pco2 Involuntary 1 Pons 2 VRG 3 Medullary chemoreceptor 4 Sensory neuron 5 Carotid chemoreceptor 6 Somatic motor neuron expiration 7 Aortic chemoreceptor 8 Internal intercostals 9 Abdominal muscles 10 Diaphragm 11 External intercostals 12 Scalenes sternocleidmastoids 13 Somatic motor neuron inspiration 14 DRG 15 Limbic system 16 Higher brain centers emotions voluntary control Vagus Glossopharyngeal Nerve NTS Nucleus Tractus Solitarius Maintains upper airway open Intercostal nerve Larynyx Pharynx Tongue Phrenic nerve Figure 18 16 Activation of Inspiratory Neurons Some neurons fire to contract upper airway to slow flow Figure 18 17 Carotid and Aortic Body Oxygen Sensor Peripheral Chemoreceptor Oxygen is not very responsive for everyday arterial oxygen must drop below 60 mmHg to elicit a response such as high altitude and COPD Activation PCO2 pH Child holding their breath Figure 18 18 Central Chemoreceptor Ventral Surface of Medulla Central chemoreceptors are adaptive to high Pco2 over time and the patient may loose that control An emphysema patient that looses response to low carbon dioxide if given too much oxygen stop breathing Athlete competing in a race Figure 18 19 Regulation of Respiration glossopharyngeal vagus Metabolic acidosis increase VA Regulation of Ventilation IX X Alpha motor neurons PO2a 100 PCO2a 40 pHa 7 4 VE Regulation of Ventilation Small changes have effects on ventilation CO2 Not O2 CO2 Effective Control Swimmers hyperventilate CO2 limited O2 Safety Zone Interaction between O2 and CO2 in Regulation of Respiration Hypoxia 3ml VA mmPaO2 Hypoxia enhances the sensitivity of the CO2 control mechanism 20 60 Hypercapnia 40 Asphyxia summation of effect Effect of H on Ventilatory Response to C02 H stimulates the peripheral chemoreceptor Alters response to PaCO2
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