Ch. 17 "Gas Exchange and Breathing"

what are the 2 respiratory system buffers?

-hemoglobin -bicarbonate ions

describe what the Arterial-Venous O2 Difference on a Oxyhemoglobin Dissociation Curve tell us? -when does it change?

-tells us the percent of O2 that was unloaded by Hb to tissues -changes when metabolic demands changes

describe how the partial pressure of O2 & CO2 changes as it is transported from the *pulmonary arteries* to the *alveoli* to the cells & back to the *alveoli*

1. *pulmonary arteries* ppO2='s 40 mm Hg -ppCO2 ='s 46 mm Hg 2. blood moves into *alveoli* (ppO2='s 100 mm Hg, ppCO2='s 40) --> O2 moves down into the blood --> CO2 moves down into the alveoli 3. blood moves into pulmonary veins > heart > systemic arteries > *TISSUE* (ppO2='s 40, ppCO2='s 46) --> O2 moves down into tissue & CO2 moves down into blood

describe CO2 "off loading" in the pulmonary circuit

1. CO2 diffuses from blood in pulmonary capillaries (venous blood) down into lower [PCO2] --> decreases blood PCO2 2. low blood PCO2 causes bicarbonate & H ions to convert to *carbonic acid* --> + Carbonic Anhydrase --> CO2 + H20 3. this CO2 diffuses into alveoli 4. Bicarbonate levels in RBC declines, bicarbonate from plasma enters in exchange for Cl- --> more CO2

describe what occurs in acute exposure to high altitude

1. Low PO2 in alveoli 2. hypoxemia --> hypoxia 3. chemoreceptors --> increased ventilation 4. *respiratory alkalosis* : decrease PCO2 5.Bohr effect (increase affinity for O2) - increased *2,3BPG*(occurs when there is low O2) decreases affinity for O2

what are the factors that affect Hb affinity for O2?

1. body temperature (high temp='s low affinity, lose O2 for metabolism) 2. pH (low pH ='s more acidic ='s more CO2) 3. PO2 & PCO2 (high PO2='s high affinity, high PCO2 ='s low affinity) 4.2, 3-BPG ( high ='s low Hb affinity for O2)

what occurs in response to an acid-base homeostasis disturbance where there is *hyperventilation* (decrease PO2)

1. inhibition of arterial & CSF chemorecpetors 2. decreased respiratory rate -RENAL: H+ generation, bicarbonate ion secretion 3.increased PCO2 4. homeostasis

what do the gradients for gas diffusion depend on?

1. partial pressure of gases 2. solubility of gases in liquid

what occurs in response to an acid-base homeostasis disturbance where there is *hypoventilation* (increase PO2)

1. stimulation of arterial & CSF chemorecpetors 2. increased respiratory rate -RENAL: H+ secretion, bicarbonate ion generation 3.decreased PCO2 4. homeostasis

how far into the capillary do partial pressure of O2/CO2 equilibrate? -why?

1/3rd into the capillary length -to account for increase blood volume during times of exercise

describe how CO2 is transported in the blood

5% dissolved in plasma 5% bound to hemoglobin (carbaminohemoglobin) 90% dissolved in plasma as bicarbonate ions (HCO3-)

every liter of arterial (O2 blood) contains how much O2? -how much is directly/indirectly attributing to the PO2?

='s 200mL of O2 - 3mL dissolved in plasma -197 mL dissolved

define what 2,3-BPG is

='s a chemical formed inside RBC during glycolysis -upregulated when there is low O2

define Respiratory Quotient (RQ) -equation -how to asses if someone is at max RQ?

='s comparison of the mount of CO2 produced vs amount of O2 consumed by cells/tissues -max RQ (during exercise) ='s 1.1 * RQ = (VCO2)/(VO2) *

define Haldane effect -what does this say about the amount of CO2 in systemic veins/pulmonary circuit

='s deoxyhemoglobin has greater affinity for CO2 compared to oxyhemoglobin -increase PO2 ='s decrease Hb affinity for CO2 -*systemic veins* (PO2='s 40 mm Hg)='s more affinity for CO2 - *pulmonary circuit* (PO2 ='s 100mm Hg) ='s less affinitey for CO2

define chemoreceptors -FUNCT

='s detect changes in partial pressures of arterial O2 & CO2 --> relay info to medulla

define the Bohr effect

='s pH is directly proportional towards Hb affinity for O2 -higher pH (alkalinic) ='s greater affinity -lower pH (acidic) ='s lower affinity

define what is the chloride shift and why it is important

='s when bicarbonate ions get transferred for Cl- ions -important so that CO2 can be continuously be transported into RBC & converted

describe the VPR mismatch that occurs throughout the lungs: base/apex

APEX: -VPR='s > 1 -higher ventilation, lower perfusion BASE: -VPR < 1 -higher perfusion, lower ventilation

what is the saturation rate & PO2 of hemoglobin for O2 in arterial and mixed venous blood?

Arterial blood: 98.5%, 100 mm Hg Mixed venous blood: 75%, 40 mm Hg

describe the reversible CO2-carbonic acid-bicarbonate reaction

CO2 (produced from active tissue) + H2O (plasma/ICF) <--*carbonic anhydrase*--> H2CO3 (*carbonic acid*) <--> H+ +HCO3- (*bicarbonate ion*)

At rest, how much O2 do cells use? how much CO2 produced? RQ at rest?

CO2 ='s 200 mL/min O2 ='s 250mL/min RQ ='s .8

is CO2 or O2 more soluble in liquid? -by how much? -what does this mean?

CO2 is 20x more soluble -means there is a higher concentration of CO2 in water

describe FUNCT of Carbonic Anhydrase -where is it found?

FUNCT: convert CO2 into Carbonic acid --> immediately dissociates in H+ & bicarbonate ion -found in RBC

Why does the APEX of the lung have a higher ventilation and lower perfusion?

HIGH Ventilation: -intrapleural cavity volume is larger --> decreases Pip --> increase Ptp LOW Perfusion: -blood flow has to flow against gravity up in lung

describe the reversible equation for oxyhemoglobin & deoxyhemoglobin -having a high PO2 means you have more oxy/deoxy-hemoglobin?

Hb + O2 <--> Hb O2 (oxyhemo) -high PO2 ='s oxyhemoglobin

Why does the BASE of the lung have a lower ventilation and higher perfusion?

LOW Ventilation: -intrapleural cavity volume is smaller --> increases Pip --> decreases Ptp HIGH Perfusion: -blow flow is with gravity down the lung

describe the different respiratory control centers in the brainstem

MEDULLA: -Ventral Respiratory Group (VRG) -Dorsal Respiratory Group (DRG) --> active only in inspiration PONS: -Pontine Respiratory Group (PRG) --> mixed neurons active in both exp/insp

what is the partial pressure of O2 & CO2 in the alveoli

O2 ='s 100 mm Hg CO2 ='s 40 mm Hg

what is the partial pressure of O2 & CO2 in the pulmonary arteries?

O2 ='s 40 mm Hg CO2 ='s 46 mm Hg

what is the partial pressure of O2 & CO2 in the cells?

O2='s 40 mm Hg CO2 ='s 46 mm Hg

define Carbamino effect

PCO2 is inversely proportional to Hb affinity for O2 -high PCO2 ='s low affinity

define hyperventilation

a condition in which ventilation *exceeds* the metabolic demands of the body -breathe off too much CO2 -breathe in too much O2

define hypernea

an increase in ventilation *to meet* an increase in the metabolic demands of the body

where in the lung would you find low PCO2 and high PO2? -what does this lead to?

apex of lung -bronchoconstriction -arteriolar dilation

where in lung would you find high PCO2 and low PO2? -what does this lead to?

base of lung -bronchodilation -arteriolar constriction

where are central/peripheral chemoreceptors located? -where does it receive info from?

central: dorsal medulla, receives info from cerebrospinal fluid peripheral: carotid bodies, receives info from arterial blood

define hypoventilation

condition in which ventilation is *insufficient* to meet metabolic demands of body

define how the partial pressure of a single gas in gaseous mixture is determined

determined by the product of: 1. the fractional concentration of that gas with the mixture 2. total pressure exerted by the gas mixture

what does the Henderson-Hasselbach Equation describe?

explains that we need to keep pH stable by having a 20:1 ratio of bicarbonate ions and CO2 molecules

define difference between hypoxemia hypoxia

hypoxemia: low blood O2 hypoxia: low tissue O2

what does a Ventilation-Perfusion rate less than/more than to 1 mean?1

less than 1 ='s wasted blood flow more than='s wasted air flow

what does a Oxyhemoglobin Dissociation Curve look at? -what occurs as PP of O2 rises?

looks at Hb's saturation with O2 as a function of PP of O2 -as pp of O2 rises, Hb rate of saturation also rises

define normal pH values for blood -acidosis -alkalosis *effect on CNS

normal: 7.38-7.42 acidosis: pH < 7.35, CNS depression alkalosis: pH > 7.45, CNS excitation

what are the inspiratory neurons?

phrenic: innervates diaphragm external intercostal nerve

describe what different sections of Oxyhemoglobin Dissociation Curve mean -what does this say about Hb affinity for O2?

pp O2: < 15 mm Hg ='s very low affinity 20-40 mm Hg ='s positive cooperativity, very high affinity for O2 --> steep curve >60 mm Hg ='s less available binding sites or O2 --> approaching saturation

differentiate between FUNCT of pulmonary artery/vein

pulmonary artery='s deoxygenated blood into the lungs pulmonary veins='s oxygenated blood into the heart

define polycythemia

too much RBC in system w/o increase in plasma -increase blood viscosity -increase BP