CBIO 2210 weeek 9 notes
CBIO 2210 weeek 9 notes CBIO2210
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This 8 page Class Notes was uploaded by Elise Weidner on Wednesday March 30, 2016. The Class Notes belongs to CBIO2210 at University of Georgia taught by Rob Nichols in Spring 2016. Since its upload, it has received 10 views. For similar materials see Anatomy and Physiology II in Anatomy at University of Georgia.
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Date Created: 03/30/16
CBIO2210 Notes 3/15/16 External Respiration Membranes involved in respiration: o Squamous alveolar cell o Shared basement membrane o Capillary endothelial cell Dalton’s law o The atmosphere is a mixture of gases. o Each gas in the mixture contributes “its part” of the whole mixture. o The whole mixture has a total pressure (760 mm Hg @ MSL(mean sea level)) each gas in the mixture contributes a partial pressure to this total o Each gas has its own partial pressure that is proportional to the percentage of the mixture that it makes up. for example, the PN2(partial pressure of nitrogen) (at sea level) = 760 mm Hg x 0.786 = 597 mm Hg this is how we get the term “partial pressure” Gas Exchange (Respiration) o Another component of Dalton’s Law is that each gas in the mixture follow its own pressure gradient. Consider: the partial pressure gradient for O2 in the lungs is steep: PO2 in pulmonary arterioles = 40 mm Hg (top arrow) PO2 in alveoli = 104 mm Hg (lower arrow) So, which way does O2 move? o Move down pressure gradient, from high to low o O2 moves from air into the blood o PCO2 gradient in lungs is less steep: pulmonary arterioles = 45 mm Hg (top arrow) alveoli = 40 mm Hg (bottom arrow) o Which way will CO2 move? From blood to air because it is going down its pressure gradient o Notice the gradient is significantly less (lower ΔP). o CO2 has a greater solubility in liquids than oxygen does so it dissolves faster into the blood and at a lower ΔP than O2). External: Blood returning to heart still has a little CO2 in it because once it reaches equilibrium with the O2 and CO2 in the alveoli (air) there is no more pressure gradient when it is equal Internal: The O2 going into the tissues is used in cellular respiration to make water, the CO2 comes from the glucose in the tissues. o Transit Time-how long it takes for volume of blood to go from top of capillary bed to bottom (where gas exchange takes place) While exercising the transit time is around 0.3 seconds because the heart beats faster and the blood flows faster At rest it is around 0.75 seconds o Rate of gas diffusion is: directly proportional to the partial pressure gradient of the gas (higher the delta P, the faster the O2 and CO2 will move) directly proportional to the respiratory membrane surface area (progressively lost in diseases like emphysema) inversely proportional to the thickness of the respiratory membrane (increased in inflammatory diseases (bronchitis) and with additional fluid or mucus) o So, the greater the pressure gradient, and the thinner the membrane, the faster a gas can diffuse Transport of Respiratory Gases o Hemoglobin has a limit of holding 4 oxygen, if it has all 4 it is saturated o Oxyhemoglobin- o Deoxyhemoglobin o Carbaminohemoglobin (20% of the CO2 in the blood) o As partial pressure of O2 in air in mm HG increases, % O2 saturation of hemoglobin increases (graph) Typically reach equilibrium before saturation Equilibrium (how much O2 can come based on pressure gradient) Saturation(how much O2 can come based on molecular bonding cites available to bind to CBIO2210 Class Notes 3/17/16 Top Hat Questions 1. The exchange between blood and interstitial fluid of the blood tissues is known as: a. Internal respiration b. External respiration 2. If the partial pressure of carbon dioxide in the tissues is __mmHg, and it is____mmHg in the blood, then carbon dioxide will move from tissues into the blood. a. 55;45 b. 40;100 c. 55;55 d. 25;50 3. During vigorous exercise, RBCs spend 0.3s in an alveolar capillary (compared to 0.75s at rest). In alveolar capillaries, RBCs would be able to load ___% of the O2 in the 0.3s of exercising compared to normal (0.75s). a. 25 b. 75 c. 40 d. 100 e. 80 Oxygen-Hemoglobin Dissociation Curve Illustrates the relationship btw P O2 and O2 binding to hemoglobin At higher levels of P O2 hemoglobin tends to hold onto O2 very tightly At lower oxygen levels the hemoglobin does not hold the oxygen as tightly Transport of Respiratory Gases: O2 Loading and unloading of O2 by hemoglobin is regulated by: o PO2 (partial pressure) o temperature in warmer tissues hemoglobin has looser relationship with O2, will let go more often (happens when exercising) in cooler tissues the reverse is true o blood pH (the Bohr effect: the normal curve is shifted to the right in exercising or oxygen-depleted tissues) in a slightly acidic environment (lower pH) the hemoglobin has a looser hold on O2 (Bohr effect) (this happens when exercising) H+ weaken the bond between hemoglobin and O2 o PCO2 (partial pressure CO2) 7 - 10% CO2 dissolved in plasma (more able to do this than O2) 20% CO2 bound to hemoglobin (carbaminohemoglobin) Binds to protein aspect of hemoglobin not the heme group like O2 Haldane effect: deoxygenated blood has an increased ability to bind to CO2 Blood in peripheral tissue capillaries has lower O2 sats and can thus carry more CO2 back to lungs 70% as bicarbonate ions in plasma carbonic anhydrase is an enzyme abundant in RBCs, reversibly catalyzes: o CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3 – Yellow part: bicarbonate buffer system Bicarbonate (far right)=product of water and CO2 Direct relationship btw pH and P CO2 levels, inverse relationship, but direct If P CO2 goes up higher than normal what will happen to pH? o Up o Down (b/c producing excessive amounts of CO2) o same Main buffer system in body to keep pH of blood around 7.35 Underlined part: carbonic acid Haldene effect (he will post about this later) O2 Loading O2 Unloading Internal respiration External respiration CO2 and Blood pH Slow breathing, shallow breathing (or exercise) allows CO2 accumulation leading to a pH drop (CO2 is converted to carbonic acid by CA) Pontine respiratory centers o Clusters of cell bodies in the pons Ventral respiratory group Dorsal respiratory group Brain stem monitors pH changes (central chemoreceptors): o can manipulate ventilation to compensate for pH changes caused by disturbances in metabolism What would be the effects of the following on blood pH? o increased ventilation (breathing faster) getting rid of more CO2 (P CO2 goes down) so pH increases o decreased ventilation (breathing slower) pH decreases the blood accumulates CO2 (retains CO2) o if a patient is breathing fast they probably have a decreased pH (too much CO2) so they are trying to get rid of CO2 Control of Respiration Central chemoreceptors in medulla o respond primarily to changes in pH in brain tissue and CSF o i.e., control of breathing is primarily about regulating [H+] in the brain Peripheral chemoreceptors in aortic arch and carotid bifurcation o respond to changes in PO2 o require significant drop in PO2 to stimulate changes in breathing o as such, are considered to only “enhance the sensitivity” of the central chemoreceptors Arterial blood leaving the longs has P O2 around 100-140mmHg o The main stimulus for breathing is not for need of levels of O2 o It takes a huge drop in arterial oxygen (below 65 mmHg) to get response to breath faster o It is usually a need to get rid of CO2 or drop in pH COPD Both pathologies usually start from smoking tobacco, small number can be carried genetically “blue bloaters” –chronic bronchitis o Causes dyspnea-difficulty breathing o fluid accumulation in alveoli impairs oxygenation o cyanotic-mucus blocks ability to get O2 in to blood and CO2 out of blood (makes blood darker and skin turns a different shade, usually in nailbeds) o lung volume increases, barrel chested appearance as expands o bronchial collapse impairs expiration leading to air trapping and chest expansion “pink puffers” -emphysema o reduction of alveolar surface area and elasticity leads to easy inflation but impaired expiration o use forced expiration to exhale o musculature is well toned so patient is less bloated o don’t have mucus trapping air like bronchitis o thoracic pressure results in transient forced oxygenation of blood and lack of cyanosis frequent infections caused by both