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34 Cards in this Set
- Front
- Back
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4 Factors Affecting Diffusion in the Respiratory System
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Remain constant under normal conditions: - surface area - membrane thickness - diffusion distance Most important factor: - concentration gradient |
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Conditions Affecting Movement of Gases
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Pressure gradient Solubility Temperature |
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Partial Pressure Changes of O2 at Alveoli and Systemic
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PO2=100mmHg in alveoli PO2=100mmHg in arteriole flow Drops to 40mmHg at peripheral tissue (PO2 at peripherial tiss < 40mmHg) PO2=40mmHg in venous flow |
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Partial Pressure Changes of CO2 at Alveoli and Systemic
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PCO2=40mmHg in alveoli PCO2=40mmHg in arteriole flow Increases to 46mmHg at peripheral tissue (PCO2 at peripheral tiss > 46mmHg PCO2=46mmHg in venous flow |
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Classifications of Hypoxias
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Hypoxic Hypoxia: low arterial PO2 (high altitude) Anemic Hypoxia: decreased O2 bound to Hb (bld loss, anemia, CO poisoning) Ischemic Hypoxia: reduced bld flow (hrt failure, shock, thrombosis) Histotonic Hypoxia: failure of cells to use O2, due to poisoning (cyanide or other poisons) |
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Causes of Low Alveolar PO2
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Air is abnormally low in O2 content (altitudes) Alveolar ventilation is inadequate - decreased lung compliance - increase airway resistance - drug overdose affecting elasticity |
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Pathological Conditions Affecting Alveolar Ventilation
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Emphysema: decreased surface area for diffusion Fibrotic Lung Disease: decrease compliance due to scar tissue Pulmonary Edema: increased diffusion distance Asthma: bronchiole constriction |
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Fused Membrane
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Tissue located between the alveoli and the capillary
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Pathway of Gas From Alveoli to Bld Vessel
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Alveolar air space Cross alveolar epithelium (simple squamous) Cross fused membrane Cross capillary tissue (simple squamous) Into capillary lumen |
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O2 Pathway From Alveoli to RBC
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Alveolar space Diffuse across alveolar epithelial cells Across fused membrane Across capillary endothelium Into plasma (2%) Diffuses into RBC and bonds to Hb (98%) |
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O2 Pathway from RBC to Peripheral Tissue
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Hb releases O2 into plasma Diffuses into cells for cellular respiration |
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Transport of O2 to Systemic
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2 methods: 1) dissolved in plasma (2%) 2) bonded to Hb (98%) |
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Physical Factors Affecting Hb's Affinity for O2
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Decrease affinity, increase dissociation, decrease saturation Factors: - pH - Temp - PCO2 - 2,3-DPG |
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pH and CO2 Effect on Hb's Affinity for O2
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Decrease pH = increase CO2 (more acidic) dec. saturation, inc. dissociation, dec. affinity |
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Temperatures Effect on Hb's Affinity for O2
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Increase temp dec. saturation, inc. dissociation, dec. affinity |
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2,3-DPG Effect on Hb's Affinity for O2
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Increase 2,3-DPG inc. dissociation, dec. affinity, dec. saturation |
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Influences O2 Dissolved Into Plasma
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Composition of air (altitudes) Alveolar ventilation - rr and depth - airway resistance - lung compliance O2 diffusion between alveoli and bld - surface area - diffusion distance (memb thickness & interstital fluid amount) Adequate perfusion of alveoli (flow) |
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Influences of O2 Binding to Hb
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% saturation of Hb - PCO2, pH - Temp - 2,3-DPG Total # of binding sites - Hb content per RBC - # RBCs |
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Transport of CO2 from Systemic
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3 methods: 1) dissolved in plasma (7%) 2) bonded to Hb (23%) 3) H2CO3 -> H+ + HCO3- (70%) - carbonic acid dissociates to H+ and bicarbonate |
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CO2 Pathway from Tissue to RBC
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CO2 diffuses into plasma 7% dissolved in plasma 23% into RBC w/ Hb 70% into RBC then into plasma as HCO3- |
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CO2 Pathway from Blood to Alveoli
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Hb releases CO2, dissolves into plasma HCO3- into RBC->Carbonic Acid->H2O and CO2 - dissolves into plasma Dissolved CO2 crosses capillary endothelium Crosses fused membrane Crosses alveoli epithelium into alveoli space |
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Carbonic Acid Formation in RBC
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Tissue Side: - CO2 dissolves into RBC - CO2 + H2O -> H2CO3 (w/ carbonic anhydrase) - HCO3- exits into plasma antiport w/ Cl- - H+ binds w/ Hb Alveoli Side: - HCO3- exits into RBC / Cl- out - H+ from Hb to form H2CO3 - H2CO3-> H2O + CO2 (w/ CA) - CO2 dissolves into plasma |
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Stimuli for Reflex Control of Ventilation
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1) emotions and voluntary control 2) CO2 3) O2 and pH and CO2 |
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Emotion and Voluntary Control of Ventilation
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Cerebral cortex Limbic system M.O. and pons (regulation center respiration) Somatic motor neurons - Inspiration (scalene, SCM, ext. intercostals, diaphragm) - Expiration (int. intercostals, ab muscles) |
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CO2 Reflex Control of Ventilation
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Medullary chemoreceptors M.O. and Pons Somatic motor neurons - Inspiration (scalene, SCM, ext. intercostals, diaphragm) - Expiration (int. intercostals, ab muscles) |
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CO2, O2 and pH Reflex Control of Ventilation
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Carotid and Aortic chemoreceptors Afferent sensory neurons M.O. and Pons Somatic motor neurons - Inspiration (scalene, SCM, ext. intercostals, diaphragm) - Expiration (int. intercostals, ab muscles) |
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3 Reasons Why CO2 Affects Ventilation
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Influences Medullary chemoreceptors (central) Influences Carotid/aortic chemoreceptors (peripheral) Affects pH |
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Respiration Regulation Center of Brain
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Pons - PRG center (pneumotaxic and apneustic) - depth of breathing (freq. and amnt of neurox) Medulla Rhythmicity Centers - VRG: output to expiratory, some inspiratory muscles - DRG: output to inspiratory muscles |
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Peripheral Chemoreceptors
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Located in carotid and aortic arteries Composed of specialized glomus cells - sense changes in PO2, pH and PCO2 |
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Chemoreceptor Response to CO2 levels
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Increased Plasma PCO2 Increased PCO2 in CSF - decreased pH-> Central chemoreceptors - increased ventilation - increase PO2 and decreased PCO2 (- feedback) Increased PCO2 in arterial - decreased pH-> Peripheral chemoreceptors - increased ventilation - increase PO2 and decreased PCO2 (- feedback) |
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Protective Reflexes of Respiratory System
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Irritant receptors - bronchoconstriction - sneezing - coughing Hering-Breuer Inflation Reflex - auto response to minimize lung stretch |
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Pontine Respiratory Group (PRG)
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Regulation center within the Pons Regulates the depth of breathing by freq of neuron firing and amount of neuroxmitter released. Influences VRG and DRG 2 Centers: 1) pneumotaxic 2) apneustic |
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Ventral Respiratory Group (VRG)
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Rhythmicity center in medulla Controls expiratory muscles, some inspiratory |
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Dorsal Ventral Group (DRG)
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Rhythmicity center in medulla Controls inspiratory muscles Feedback to PRG |
