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81 Cards in this Set
- Front
- Back
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diffusion rate
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dp to surface area
dp to concentration gradient idp to membrane thickness idp to diffusion distance |
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the most important factor for gas exchange is
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concentration gradient
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when gas is placed in contact with water and there is a pg then
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gas molecules will move from one phase to the other
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the movement of gas molecules from air into liquid is dp to 3 factors
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pg of gas
solubility of gas in the liquid temperature (which will be ignored) |
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what occurs at equilibrium
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pressure of o2 is equal in air and in water but concentration is not necessarily the same
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carbon dioxide solubility
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20x more than oxygen in water
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oxygen diffusion
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from alveoli to peripheral tissue... normal alveoli is 100 mm in alveoli and 40 in cells
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co2 diffusion
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pco2 is higher in tissues than in systemic capillary blood becaues of co2 production during metabolism
cellular pco2 is 46 while arterial plasma is 40 |
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hypoxia and hypercapnia
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state of too little oxygen
state of too much co2 |
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low arterial oxygen content problems
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inadequate oxygen reaching the alveoli
-problems with oxygen exchange btw alveoli and pulmonary capillaries -inadequate transport of oxygen in the blood |
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hypoxic hypoxia
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low arterial po2 caused by high altitude, decreased lung diffusion capacity
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anemic hypoxia
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decreased total amount of o2 bound to hemoglobin caused by blood loss, carbon monoxide poisoning
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ischemic hypoxia
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reduced blood flow caused by heart failure
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histotoxic hypoxia
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failure of cells to use o2 because cells have been poisoned caused by poisons especially cyanide
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what does a decrease in alveolar po2 do?
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decreases oxygen uptake at the lungs
1) inspired air has abnormally low oxygen content 2)alveolar ventilation is inadequate |
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the main factor that affects the oxygen content of inspired air is
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altitude
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low alveolar ventilation is known as
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hypoventilation
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normal lung has
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normal po2
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emphysema
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destruction of alveoli reduces surface area for gas exchange
po2 normal or low po2 low |
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fibrotic lung disease
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thickened alveolar membrane slows gas exchange
loss of lung compliance may decrease alveolar ventilation po2 is low or normal po2 is low |
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pulmonary edema
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fluid in interstitial space increases diffusion distance. arterial pco2 may be normal due to higher co2 solubility in water
po2 is normal for exchange surface but low for vent? |
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asthma
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increased airway resistance decreases airway ventilation
-bronchioles constrict -po2 is low 2x |
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why is diffusion distance usually small?
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becasue cells are thin and there is little or no interstitial fluid btw the two cell layers
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pathological changes adversely affect gas exchange include
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a decrease in the amount of alveolar surface area available for gas exchange
-an increase in teh thickness of the alveolar membrane -an increase in the diffusion distance btw the alveoli and the blood |
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gas exchange btw the lungs is
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rapid and blood flow thru the pulmonary capillaries is slow
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in emphysema which is a degenerative lung disease there is a
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there is a physical loss of alveolar surface
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diffusion of gases through scar tissue is
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much slower than normal
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because the lungs have a built-in reserve capacity...
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1/3 of the exchange epithelium must be incapacitated before arterial Po2 falls significantly
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diffusion distance btween the alveoli and blood increases in this pathological condition
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pulmonary edema, which is characterized by excessive interstitial fluid volume in the lungs
-normally only small amount of isf are present in the lungs which result in effective lymph drainage and low pulmonary blood pressure. |
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when capillary hydrostatic pressure increases
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more fluid filters out of the capillary
-if too much filtration, the lymphatics are unable to remove all the fluid and excess accumulates in the pulmonary interstitial space, creating pulmonary edema |
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co2 is relatively soluble in body fluids so the increased diffusion distance may
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not have a significant on co2
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HAPE
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major cause of death from altitude sickness
high pulmonary arterial pressure, extreme shortness of breath, and sometimes a productive cough yielding a pink, frothy fluid |
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oxygen is transported in 2 ways in the blood
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dissolved in plasma
bound to hemoglobin hb + o2 <=> HbO2 |
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plasma Po2 increases where and how
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in pulmonary capillaries as oxygen diffuses in from the alveoli
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plasma Po2 falls where
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at the cells and hb gives up its oxygen
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the majority of oxygen is bound to
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hb 98% and transported inside of rbc
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total arterial O2 carrying capacity =
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3 mL dissolved O2/L blood +
197 mL HbO2/blood = 200 |
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what happens if cardiac output remains at 5 L/min?
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then the hemoglobin-assisted oxygen delivery to cells is almost 1000 mL/min
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the amount of oxygen that binds to hemoglobin depends on 2 factors
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the Po2 in the plasma surrounding the RBC
-the number of potential binding sites available in the RBC |
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what is the primary factor determining available hemoglobin binding sites that are occupied by oxygen?
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plasma Po2
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arterial Po2 is established by
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composition of inspired air
alveolar ventilation rate efficiency of gas exchange from alveoli to blood |
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hemoglobin adults v. fetus
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adults: 2 alpha and 2 beta
fetus: 2 alpha and 2 gamma |
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oxygen-hemoglobin binding obeys the law of mass action
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if you increase oxygen conc., then the reaction shifts to the right
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what determines oxygen-hb binding?
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the Po2 of plasma surrounding the red blood cells
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what happens when cells increase their metabolic activity?
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Po2 decreases and hb releases more oxygen to them
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percent saturation of hb
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the percentage of available binding sites that are bound to oxygen
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oxygen-hb dissociation curve
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the percent change is much greater at lower percentages than near saturation
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what affects oxygen-hb binding?
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temperature
ph metabolites |
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increased temperature
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will decrease the affinity of hb for oxygen and shift to the right
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decreased pH
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will decrease the affinity of hb for oxygen and shift to the right
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will decrease the affinity of hb for oxygen and shift to the right
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increased Pco2
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what happens when you exercise?
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anaerobic metabolism produces lactic acid which in turn releases H+ into cytoplasm and ecf causing an increase in H+ and decrease in pH thus decreasing the affinity of hb for oxygen, and shift to the right
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bohr effect
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a shift in hb saturation curve that results from a change in pH
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what happens when you experience chronic hypoxia which is an extended period of low oxygen?
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chronic hypoxia increases 2,3-DPG in RBC which lowers binding and shifts curve to the right
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fetal hb v maternal hb
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fetal hb has a higher binding affinity
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Co2 transport
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7% carried by venous blood is dissolved in the blood
-93% diffuses into RBC -70% is converted to bicarbonate ion -23% binds to hb |
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why is removing CO2 from the body so important?
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elevated Pco2 (hypercapnia) causes the pH disturbance known as acidosis leading to denaturing of proteins and depression of CNS
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why convert Co2 to HCO3?
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provide an additional means by which Co2 can be transported from cells to lungs
-HCO3 is available to act as a buffer for metabolic acids thereby helping stabilize the body's pH |
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how does co2 turn into hco3
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carbonic anhydrase
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total arterial o2 content is divided into
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oxygen bound to hb
oxygen dissolved in plasma (Po2 of plasma) |
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oxygen bound to hb
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% saturation of hb
total number of binding sites |
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% saturation of hb
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pCo2
pH temperature 2,3-dpg |
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total number of binding sites
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hb content per RBC
number of RBCs |
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oxygen dissolved in plasma
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composition of inspired air
alveolar ventilation oxygen diffusion btw alveoli and blood adequate perfusion of alveoli |
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carbonic anhydrase does what to co2 and water?
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forms carbonic acid h2co3 which then dissociates into H+ and hco3-
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two separate mechanisms remove free H+ and HCO3
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1) chloride shift- exchanges 1 hco3 for 1 cl while maintaining electrical neutrality
2)hb acts as a buffer for preventing large changes in body's pH but if pCO2 is elevated, H+ causes respiratory acidosis |
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Co2 and H+ ___ hemoglobin's binding affinity for oxygen
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decreases
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contraction of skeletal muscles
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not able to contract spontaneously, must be initiated by somatic motor neurons
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contraction of diaphragm and intercostals
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initiated by groups of neurons in the pons and medulla of the brain stem
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model for control of ventilation
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respiratory neurons in the medulla control inspiration and expiration
-neurons in the pons modulate ventilation -rhythmic pattern of breathing arises from a network of spontaneously discharging neurons -ventilation is subject to modulation by various chemoreceptor-linked reflexes |
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neurons in the medulla control
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breathing
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ventilation pattern depends on the levels of ___ in the ecf
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Co2
O2 H+ |
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dorsal respiratory group of neurons contain
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mostly inspiratory neurons that control the diaphragm
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ventral respiratory group of neurons control
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muscles used for active expiration and some inspiratory muscles
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central pattern generator
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pons
medulla oblongata -drg -vrg |
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somatic motor neurons for inspiration
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scalene and stenocleidomastoid
external intercostals diaphragm |
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somatic motor neurons expiration
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internal intercostals
abdominal muscles |
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what 3 things influence ventilation?
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Co2 the primary stimulus for changes in ventilation
O2 pH |
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what triggers an increase in ventilation
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decrease in Po2 or pH
increase in PCO2 |
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hering-breuer inflation reflex
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prevents overexpansion of the lungs during strenuous exercise
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irritant receptors
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send signals thru sensory neurons to control centers in the CNS that trigger bronchoconstriction
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