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Respiratory Physiology TV- (VT) – Tidal volume – amount of air inspired and expired at rest =500ml ERV- expiratory reserve volume – amount of air that can be expired beyond TV =1200ml IRV – inspiratory reserve volume- amount of air that can be inspired beyond TV = 3100ml RV- residual volume- remains in lungs after forced expiration = 1200ml *a fraction of this, called minimal volume, remains even in a collapsed lung TLC –total lung capacity =6000ml TV+IRV+ERV+RV IC – inspiratory capacity TV+IRV = 3600ml maximum amount that can be inspired after normal expiration VC – vital capacity TV+IRV+ERV = 4800ml amount that can physically be inspired or expired FRC – functional residual capacity volume remaining in lungs after normal tidal volume expiration RV+ERV=2400ml Anatomic dead space – volume of air remaining in conducting portion of respiratory system per breath 30% of TV (150ml) Minute ventilation - total amount of air that flows into/out of the respiratory tract per minute. 12 x (TV)500ml = 6000ml AVR -Alveolar ventilation rate - part of minute ventilation that is actually used for respiration #breaths per minute(12) x (350ml) =4200ml FEV1.0 - maximum amount of air forcefully expired in first second. (80% VC is normal) Respiration types A) Pulmonary ventilation - breathing B) External respiration- exchange of gases between alveolar air/blood C) Internal respiration – exchange of gases between blood/tissues Chemical Regulation of Respiration A) Central chemoreceptors -located in medulla oblongata -respond to changes in H+ in CSF -therefore, we say they are highly sensitive to CO2 (+/- 3 mmHg) WHY? CSF has no proteins to buffer H+. In blood plasma, about 70% of carbon dioxide reacts with water H2O + CO2 H2CO3 (H+) + (HCO3-) Therefore, detecting hydrogen ion content indirectly detects carbon dioxide content More carbon dioxide = lower pH = more acidic What about the rest of CO2 ? 7% - simply dissolved in plasma 23% - forms carbaminohemoglobin Compare to oxygen: 99% bound to hemoglobin 1% dissolved in plasma PO2 and PCO2 values PO2 of deoxygenated blood= 40 mmHg PO2 of alveolar air = 105 mmHg PO2 of oxygenated blood = 100 mmHg PCO2 of deoxygenated blood = 45 mmHg PCO2 of alveolar air = 40 mmHg PCO2 of oxygenated blood = 40 mmHg • Tissue cells average • PO2 = 40 mmHg • PCO2 = 45 mmHg • 25% of oxygen derived from blood for a person at rest. 75% still carried B) Peripheral chemoreceptors -located in walls of aorta and carotid arteries -also sensitive to H+ (CO2) (+/- 3 mmHg) - also sensitive to O2 , but only substantial deficiencies (by about 40 mmHg !) Blood / gas transport physiology concepts Bohr effect - hemoglobin can act as a buffer for H+ as H+ binds to amino acids of hemoglobin. This induces shape changes and reduces hemoglobin’s O2 carrying capacity. Application: metabolically active tissues receive more O2 -why? Haldane effect – amount of CO2 transported in blood is related to the percent saturation of hemoglobin by oxygen. Deoxyhemoglobin can bind more CO2 and buffer more H+ than oxyhemoglobin. Application: deoxyhemoglobin removes H+ from solution & promotes CO2 HCO3 but oxyhemoglobin favors HCO3CO2 (alveoli) Chloride Shift - carbonic acid formation via carbonic anhydrase occurs in rbc’s . Excess HCO3 begins to diffuse to plasma, as Clions from plasma diffuse into rbc’s Application: maintains electrical balance between rbc’s and plasma Physiological terms a) Hypercapnia -- increased arterial CO2 -results in hyperventilation –why? b) Hypocapnia -- decreased arterial CO2 -results in hypoventilation and ability to hold breath for extended periods -why is this dangerous? c) Hypoxia - - decreased arterial O2 causes a decreased tissue level of O2 FOUR types: 1)hypoxic hypoxia-failure to get O2 into blood airway obstruction, CO, 2) anemic hypoxia- low hemoglobin/hematocrit anemia 3) ischemic hypoxia- failure of blood to circulate heart failure, clots 4) histotoxic hypoxia- tissues are unable to use provided O2 -cyanide