aortic bodies) locations ! Relay info of changes in pH to the brain, IF and CSF, as well as blood PO2, PCO2, and pH " PP of Co2 affects pH o Send info to brainstem, modifies rate and depth of breathing • Effects of Blood, PCO2, and pH on Ventilation: o H2O + CO2 $# H2CO3 $# HCO3 + H+ o Hypoventilation: CO2 increases, pH falls o Hyperventilation: blood CO2 quickly falls and pH rises o Oxygen: observe very little change ! Hypoventilation: large oxygen reservoirs ! Hyperventilation: arterial blood is 97% saturated o ppCO2 and pH is affected more by ventilation than by oxygen ! ventilation is adjusted to maintain constant ppCO2, with proper oxygenation occurring as a side effect of this reflex control o Note: immediate increase in ventilation due to activation of peripheral chemoR with a rise in arterial PCO2, while a sustained rise in arterial PCO2 activates central chemoR o ChemoR in medulla: most sensitive to changes in ppCO2; CO2 can cross BBB and lower pH of CSF and brain IF ! Responsible for 70-80% of the increase in ventilation in response to high PCO2 • Effects of Blood PO2 on Ventilation: o ChemoR sensitivity to PCO2 is increase by a low PO2 and decreased by high PO2 o Hypoxic drive: arterial PO2 must fall from 100 to 70 mmHg to stimulate ventilation; due to direct effect of PCO2 on carotid bodies
o Breathing increase linearly with increasing PCO2 o Body more concerned about low ppI2 than high levels o What does human body key into for respiration rate: ppCO2 o Persistently elevated PCO2 enhances sensitivity of carotid bodies to fall in PCO2 • Effects of Pulmonary Receptors on Ventilation Rate: o Higher brain centers provide you with option of voluntary breathing o Stub your toe/emotions: first response is to gasp o Irritant receptors in lungs: triggered by pollen/smoke, start to cough o Hering-Breuer Reflex: stimulated by pulmonary stretch receptors: activation during inspiration inhibits respirator control centers; makes further inspiration difficult ! Prevents overinflation, important in maintaining important respiration in newborns Hemoglobin and Oxygen Transport: • Hb: made of alpha and beta chains with a heme group in the middle o Heme group comprised of iron which can bind four oxygen • Oxygen carrying capacity of blood determined by Hb conc o Anemia: abnormally low Hb levels; cant carry as much O2 o Polycythemia: high levels of Hb, wonderful O2 carrying capacity • Loading reaction: looks at Hb that has no oxygen (deoxyHb); binds oxygen when it is present (high O2) • Unloading reaction: Happens in presence of low oxygen, high CO2; possibility of environment being acidic o Hardest to unload first oxygen • Carboxyhemoglobin: CO when it binds to Hb; binds with high affinity; CO competes with O2 (CO poisoning) • % oxyHb saturation: oxyHb/totalHb: usually 97% • Oxygen-Hb Dissociation Curve: o Relates saturation of Hb to PO2: not linear ! At rest in lungs: saturation is 98%, 20% volume of O2 unloaded in tissues
! At tissues: saturation is 75% saturated, 15% volume " ~25% released or 5% volume loss due to release in tissues •
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- Spring '15