Chapter 18: Gas Exchange And Transport

- a state of little oxygen

- it is a clinical sign not a disease

- sometimes goes in hand with hypercapnia

- elevated concentrations of carbon dioxide

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- oxygen must be equate to support areobic respiration and ATP production

- excretion of CO2 is important because high levels of CO2 are a central nervous depressant and also cause a state of acidosis

- respiratory system monitors plasma pH and sues changes in ventilation to alter pH

- the inspire air has low oxygen content

- alveolar ventilation is indequate

- altitude is the main factor that affects atmospheric oxygen

- partial pressure of oxygen in air decreases along with total atmospheric pressure as you move from sea level

- low aveolar ventilation

- lower than normal volumes of fresh air entering the alveoli

- result from decreased lung compliance, increased air resistance or CNS depressant that slows ventilation rate and decreases depth

- diffusion if most rapid over short distances

- concentration gradient between alveoli and blood as the primary factors affecting gas exchange in healthy people

- a decreases in the amount of alveolar surface area available for gas exchange

- an increase in the thickness of the alveolar capillary exchange barrier

- an increase in the diffusion distance between the alveolar air space and the blood

- phsyical loss of alveolar surface area

- degenerative lung disease most often caused by cigarette smoking

- alters its properties and slows gas exchgne

- lungs have build in reserve capacity, one third of the exchange epithelium must be incapacitate before arterial PO2 falls significantly

- accumulation of intertestinal fluid increases the diffusion dsitance and slows gas exchange

- if pulmonary blood pressure rises for some reason the normal filtration/reabsorption balance at the capillary is disrupted

- when hypoxia is due to alveolar fluid accumulation is severe and cannot be corrected through oxygen therapy

- the pressure grandient of the gas

- the solubility of the gas in the liquid

- temperature

- if gas pressure is higher in the water than gasesous phase then gas molecules leave the water

- if gas pressure is higher in the gaseous phase than in water, then the gas dissolves into the water

- the concentration of oxygen dissolved in the water at any given PO2

- the ease in which the gas dissolves in a liquid

- high solulbility = gas molecules need low gas partial pressure to go into the liquid

- low solubility = gas molecules need high partial pressure to dissolve in liquid

- oxygen is not very soluble

- oxygen's low solubility in aqeous solution means that very little oxygen can be carried in dissolved plasma

- low solubility means that oxygen is slower to cross the increases diffusion distance in pulmonary edema

- carbon dioxide in not signficatically affected by pulmonary edema because it is soluble

- red blood cells

- have a critical role in ensuring that gas transport between lungs and cells is adequate to meet cell needs

- defined as amount of X moving per minute

- concentration x volume flow

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- used to estimate cardiac output or oxgen comsumption, assuming arterial and venous blodo gases can be measured

- the oxygen that is dissolved in the plasma

- oxygen bound to hemoglobin

- carries 98% of the oxygen in blood

- reversibly binds to oxygen the central iron atom of each heme group can bind reversibly with one oxygen molecule

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- hemogloin bound to oxygen

- as the concentration of free O2 increases, more oxygen binds to hemoglobin

- if the concentration of O2 decreases the amount of oxyhemoglobin decreases

- the PO2 in the plasma surronding the red blood cells

- number of potential Hb binding sites available in the red blood cells

- the percentage of avaliable hemoglohin biding sites are occupied by oxygen

- the plasma PO2 determines the percent saturation of hemoglobin

- the composition of inspired air

- the alveolar ventilation rate

- the efficiency of gas exchange from alveoli to blood

- reflects the properties of the hemoglobin molecule and its affinity to oxygen

- as long as the alveoli stays above 60 mmHg hemoglobin is more than 90% saturated

- increased temperature, increased Pco2, or decreased pH

- decreases the affinity of hemoglobin for oxygen and shift the oxygen hemoglobin to the right

- a shift in the hemoglobin staturation curve that results from a change in pH

- when the maximal exertion that pushes cell into anaerobic metabolism

- as H+ increases, pH falls, and the affinity of hemoglobin for oxygen decreases

- a compound made form an intermediate of the glycolysis pathway

- increased levels lower the binding affinity of hemoglobin

- increase due to high altitude and anemia

- extend periods of time of low oxygen

- triggers an increase in 2,3 Diphosphoglycerate

- has two gamma protein chains in place of the two beta chains found in adult hemoglobin

- enhances the ability of fetal hemoglobin to bind to oxygen in low oxygen environment

- only 7% can dissolve in the plasma

- 93% diffuses in the red blood cells

- of the 93%, 70% is converted to bicarbonate ion and 23% binds to hemoglobin

- elevated PCO2 caues the pH disturbance as acidosis

- extremes of pH interfere with hydrogen bonding of molecules and can denature proteins

- high levels depress the CNS and cause confusion, coma, or even death

- provides an additional means of CO2 transport from the cells to the lungs

- bicarbonate is available to act as a buffer for metabolic acid thereby stabilizing the body's pH

- en enzymes found concentrated in red blood cells

- helps with the rapid conversion of CO2 into bicarbonate

- bicarbonate leaves the red blood cell on an antiport protein

- exchanges bicarbonate for Cl-

- excess H+ accumulates in the plasma

- CO2 binds with hemoglobin

- the presence of CO2 and H+ facilitates the the formation of carbamino hemoglobin and decrease its binding affinity to oxygen

- brain stem controls the breathing

- respiratory nuerons in the medulla controll inspiratory and expiratory muscles

- neurons in the pons integrate sensory information and interact with the medulla neurons to influence ventilation

- the rhythmic pattern of breathing arises from a neural network with spontaneously discharging neurons

- Ventilation is subject to continuous modulation by various chemoreceptor and mechanoreceptor linked reflexes and by higher brain centers

- control mostly muscles of inspiration

- transport output from DRG

- to the diaphragm and the intercostal nerves to the intercostal muscles

- another potine nuerons provide tonic input to medullary networks to help coordinate a smooth respiratory rythm

- of the medulla has mutlple regions with differnt functions

- contains sponteneously firing neurons that may act as the basic pacemaker for the respiratory rhythm

- inappropriate relaxation of these muscles during sleep

- a sleeping disorder associated with sleep with snoring and excessive daytime sleepiness

- located in the cartoid and arotic arteries

- sense changes in the PO2, pH, and PCO2 of the plasma

- when glomus cells sense changes, they trigger a reflex increase in ventilation

- respond only to dramatic changes in arterial PO2

- in the brain

- respond to changes in the concentration of CO2 in the cerebrospinal fluid

- actually respond to ph changes in eh cerebrospinal fluid

- respond to decrease in arterial PCO2 as well as increase

- respond by increasing ventilation

- send signals through sensory neurons to intergrating centers in the CNS that trigger bronchoconstriction