Physiology Study Guide Exam 12 Ventilation continued Air pressure dependent on Temperature Pv nRT but should remain stable in lungs blood 98 6 Like weather Heating up during day temperature change wind issues Not important factor here Gases present in partial pressures Px proportional to amount of gas present Air 79 Nitrogen little CO2 and H2O variable PO2 160 mm Hg 21 O2 PCO2 0 3 mm Hg Gases diffuse based on partial pressure Px gradients from high Px low Px Don t use concentrations b c hard to calculate volumes Numbers used for diffusion into and out of liquids from air between liquids Between alveoli and blood For blood returning to lungs via pulm veins deoxygenated PCO2 46 mm Hg PO2 40 mm Hg For air in alveoli PCO2 40 mm Hg PO2 105 mm Hg O2 into blood CO2 out to alveoli bringing waste product back But why are values off in alveoli PCO2 40 NOT 0 3 PO2 105 NOT 160 Residual volume lot of CO2 little O2 never removed from lungs average O2 average CO2 Cannot expel all used air mixes with new air entering Only time numbers are equal is when a person is first born O2 nonpolar in blood polar polarity problem 1 Little dissolved poorly soluble 1 Free O2 moving with water 2 99 reversibly bound to Hb located in RBCs Hemoglobin Hb 4 identical subunits protein made up of proteins Iron shares electrons with O2 makes reversible binding possible Need O2 to remain the same for metabolism in tissues Want transport to be like a bus get on and off the exact same Iron like seatbelt straps you in but can be taken off Cooperativity between units Shape change at 1 site changes all sites and increases affinity at others 1st O2 binding affinity at others 1st unbinding affinity at others If we were flash frozen most Hb have either no O2 s or 4 O2 s Increases O2 transferred Gradient only includes free O2 present Without Hb Free O2 6 vs 6 2 transferred With Hb Free O2 6 vs 2 10 transferred Factors affinity for O2 kick if off CO2 H Temp DPG glycolysis all change protein s shape changes shape of binding site All change shape doesn t interfere directly NOTE Question of Week What ties these all together What makes us want to have these to affinity of oxygen CO competitor binds to site Hb has much higher affinity for CO than O2 Hemoglobin saturation curve directly dependent on PO2 At PO2 pick up Lungs 100 sat Hb At PO2 drop off to tissues 80 sat Hb deoxygenated blood not unoxygenated still attached to Hb Venous reserve unused returning oxygen CPR change just chest compressions not breaths 1 Didn t want to touch lips 2 O2 already in body still just need to start up convection But only works for so long reserve as activity inverse Oxygen getting used up by cells more dropped off Can PO2 0 Yes in cells but NOT in blood Can t survive if all cells anaerobic Arterial levels in 80s sluggish 60s flat out Carbon dioxide CO2 Nonpolar but more soluble than O2 10 free CO2 30 carried on Hb Other 60 converted to bicarbonate HCO3 Via equation 3 CO2 H2O HCO3 Pro Bicarbonate is polar soluble solves transport problem to lungs Con pH issue why H Plasma is buffered system resists pH change due to Hb albumin attaches free H drives equation to products bicarbonate More bicarbonate made in blood than water Water is a better buffer Plasma adds more H per bicarbonate formed Plasma has component that binds bicarbonate Still small pH changes occur Venous pH arterial pH H H Venous side tissues making CO2 eq 2 drives equation right Eq 3 converts into bicarbonate H lowers pH CO2 offloaded in lungs Drives equation right reverse eq 3 Sent out of body during exhale Problems with Ventilation Hypoventilation too little CO2 not released too much present arterial PCO2 H HCO3 Can t bind as much O2 Causes O2 on Hb binding CO2 kicks off O2 Proteins can t function properly respiratory acidosis blood too acidic Ex In pool you breathe out underwater to acidity and be able to hold breathe longer Hyperventilation too much CO2 released arterial PCO2 H basic respiratory alkalosis Causes O2 on Hb Stays bound too much Proteins can t function right Treatment Paper bag creates pocket of CO2 to breathe more in Recall similar PCO2 levels in alveoli and blood coming back to lungs want smaller gradient to limit diffusion don t want to breathe off too much Allows us to stay in appropriate range need right pH level to do so Control of Ventilation Brainstem medulla oblongata Respiratory rhythm generator RRG section of cells that determine rate Inputs 1 Pacemaker potentials cells triggered at certain rate 2 Chemoreceptors 3 Pulmonary stretch receptors Pattern from RRG 1 Connect to skeletal muscles which are connected to regular somatic efferents and neurons from medulla oblongata RRG Stimulation contraction bigger cavity P air in expansion inspiration No stimulation relax muscles rebound of lungs P expiration Can t inhibit skeletal muscle This takes over if voluntary control messed up 2 Mechanoreceptors measure stretch in alveolar cells Large inhale heavy exercise alveolar cells can only expand so much Stretch receptors stop movement in lungs when too big Pulmonary stretch receptors activated that inhibit motor neurons Forces relaxation expiration CANNOT put adult sized bag on a child will overinflate lungs Receptors will inhibit motor neurons running diaphragm intercostals you blow lungs out from the inside Medical caused pneumothorax from the inside 3 Chemoreceptors for PO2 PcO2 and H Impact of PO2 Threshold at 60 Hb 100 99 of oxygen attached to Hb When PO2 60 Hb saturation starts ventilation rate starts Breathe more to get Hb back to full saturation Don t need to ventilation rate if Hb fully saturated 60 don t need to increase oxygen But chemoreceptors only bind free oxygen 1 Ones attached to Hb not counted by receptors No response with Changes in Hb affinity When CO attached to Hb tons of free O2 registered by chemoreceptors even though only 1 O2 CO silent killer Oxygen transport problem not registered as oxygen deficiency Losses of Hb anemia not registered by chemoreceptors to increase ventilation rate to compensate for it this 99 have no clue if problem Need more sensitivity Impact of PCO2 main system as CO2 Ventilation rate direct relationship Immediate changes sensitive to small changes But PCO2 ventilation rate crashes to 0 High levels of CO2 damaging to neurons no ventilation no message to breathe Killing method for organisms kills brain cells Impact of H due to 1 HCO3 2 Anaerobic exercise glycolysis 2 ATP lactic acid present related to CO2 levels Hard
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