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APHY 201 Exam 4b
Ch. 16 Respiratory Physiology Sec. 6-9 (VI-IX)
| Question | Answer |
|---|---|
| (bolded) What 2 factors determine the total oxygen content of the blood? | Total oxygen content depends on both the PO2 and the hemoglobin concentration. |
| (know these) What are the 5 forms of hemoglobin? | The five forms are oxyhemoglobin, deoxyhemoglobin, methemoglobin, carboxyhemoglobin, and carbaminohemoglobin. |
| What is the difference between oxyhemoglobin and deoxyhemoglobin? | Both have iron in the reduced Fe2+ form and can bind oxygen, but deoxyhemoglobin is the "reduced" form that has released its oxygen. |
| What is the abnormal form of hemoglobin with oxidized iron (Fe3+) that cannot bind to oxygen? | methemoglobin |
| What is the term for hemoglobin bound with carbon monoxide, which binds 210 times more strongly than oxygen. | carboxyhemoglobin |
| How does carboxyhemoglobin differ from carbaminohemoglobin? | Carboxyhemoglobin is bound to carbon monoxide, whereas carbaminohemoglobin is hemoglobin bound to carbon dioxide. |
| What does percent oxyhemoglobin saturation assess? | It assesses how well the lungs have oxygenated the blood by measuring the ratio of oxyhemoglobin to total hemoglobin. |
| What is the normal percent oxyhemoglobin saturation in arterial blood? | The normal value is 97%. |
| What is the condition characterized by below-normal hemoglobin levels? | anemia |
| (bolded) What is the condition characterized by above-normal hemoglobin levels, which may occur due to high altitudes? | polycythemia |
| What stimulates the production of hemoglobin and red blood cells? | The hormone erythropoietin, produced in the kidneys, stimulates production in the red bone marrow when oxygen levels are low. |
| What are the terms for the binding of oxygen to hemoglobin in the lungs, and the release of oxygen from oxyhemoglobin in the tissues? | hemoglobin "loading" versus "unloading" |
| (bolded) How does PO2 affect the direction of the oxygen-hemoglobin reaction? | High PO2 favors loading, while a lower PO2 in the tissues favors unloading. |
| (good to know) What is the PO2 and percent saturation of systemic arterial blood? | Arterial blood has a PO2 of 100 mmHg and is 97% saturated. |
| (good to know) What is the PO2 and percent saturation of systemic venous blood at rest? | Venous blood has a PO2 of 40 mmHg and is 75% saturated. |
| (highlighted) What percentage of oxygen is typically unloaded to the tissues at rest? | Approximately 22% of oxygen is unloaded, effectively emptying one of the four "seats" on the hemoglobin molecule. |
| Why is the oxyhemoglobin dissociation curve sigmoidal (S-shaped)? | The flat part at high PO2 means changes in oxygen pressure have little effect on loading, while the steep part allows small changes in PO2 to produce large changes in oxygen release. |
| How does oxygen unloading change during exercise? | Unloading increases from 22% at rest to 39% during light exercise and up to 80% during heavy exercise. |
| What is the term for the decrease in hemoglobin’s affinity for oxygen in response to low pH (high H+), which promotes oxygen release in tissues? (hint: it's an effect) | Bohr effect |
| How do pH and temperature shifts affect the oxyhemoglobin dissociation curve? | Both a decrease in pH and an increase in temperature shift the curve to the right, indicating a decreased affinity for oxygen and increased unloading. |
| What carboxyhemoglobin levels might suggest carbon monoxide poisoning? | Levels greater than 10% in smokers and 3% in nonsmokers are concerning. |
| How is carbon monoxide poisoning treated? | It is treated by breathing 100% oxygen at 1 atmosphere or higher, which helps displace the carbon monoxide from hemoglobin. |
| (emphasized) What is the specific byproduct of anaerobic glucose metabolism in red blood cells that promotes oxygen unloading? | 2,3-DPG |
| (emphasized) Under what conditions is 2,3-DPG produced? | It is produced during anemia or at high altitudes when oxyhemoglobin levels are low, shifting the curve to the right to increase oxygen delivery. |
| (emphasized) Why does fetal hemoglobin (HbF) have a higher affinity for oxygen than maternal hemoglobin? | HbF cannot bind to 2,3-DPG and has two gamma chains instead of two beta chains, allowing it to "steal" oxygen from maternal blood. |
| (starred) What are the three major factors that decrease hemoglobin affinity for oxygen and shift the curve to the right? | Decreasing pH, rising temperature, and rising 2,3-DPG. |
| in what way does pH decreasing affect the affinity of Hb for O2 and the position of the oxyhemoglobin dissociation curve? | results in decreased affinity of Hb for O2; Called the Bohr effect; increases oxygen delivery during hypercapnia |
| in what way does temperature rising affect the affinity of Hb for O2 and the position of the oxyhemoglobin dissociation curve? | results in decreased affinity of Hb for O2; Increases oxygen unloading during exercise and fever |
| in what way does rising 2,3-DPG affect the affinity of Hb for O2 and the position of the oxyhemoglobin dissociation curve? | results in decreased affinity of Hb for O2; increases oxygen unloading when there is a decrease in total hemoglobin or total oxygen content -- an adaptation to anemia and high-altitude living. |
| (certain highlighted terms) What causes the sickling of red blood cells in sickle-cell anemia? | A single amino acid mutation creates hemoglobin S, which polymerizes into long fibers when deoxygenated, distorting the cell. |
| (certain highlighted terms) Why has the sickle-cell mutation persisted in the human gene pool? | The defect imparts a high resistance to malaria because the malarial parasite cannot digest hemoglobin S. |
| (certain highlighted terms) What is the inherited defect in the production of alpha or beta globin chains, most common in people of Mediterranean heritage? | thalassemia |
| How does myoglobin differ from hemoglobin? (3 ways) | Myoglobin is found in skeletal and cardiac muscle, contains only one heme group, and has a much higher affinity for oxygen, releasing it only when PO2 is very low. |
| What are the two main functions of myoglobin? | It stores oxygen for use during muscle contraction (systole in the heart) and acts as a transfer agent between blood and mitochondria. |
| true or false, oxygen remaining in veins serves as an oxygen reserve | true |
| In what three forms is carbon dioxide carried in the blood? | Dissolved in plasma, as carbaminohemoglobin, and as bicarbonate ions. |
| What percentage of carbon dioxide is carried dissolved in plasma? as carbaminohemoglobin? as bicarbonate ions? | 7-10%, 20-23%, 70% |
| What does carbon dioxide attach to when forming carbaminohemoglobin? | An amino acid in hemoglobin (one seat for carbon dioxide on the hemoglobin bus!) |
| Where does the bicarbonate ion diffuse once it is formed in the red blood cell? | Into the plasma. |
| What do hydrogen ions (H+) attach to inside the red blood cells? | Hemoglobin (forming HHb). |
| (bolded) What is the term for the exchange of bicarbonate diffusing out of RBCs and chloride (Cl-) diffusing into RBCs? | chloride shift |
| Why is the chloride shift important? | It balances the electrical charge inside the cell by preventing too much positivity from the H+ ions. |
| How does the Bohr effect assist with oxygen unloading? | The bonding of H+ to hemoglobin lowers hemoglobin's affinity for O2, essentially kicking O2 off the hemoglobin. |
| What enables the blood to load and carry more carbon dioxide? | The bonding of H+ to hemoglobin, which allows more H+ to bind overall. |
| Where does the reverse chloride shift occur? | In the lungs (specifically the pulmonary capillaries). |
| What does increased PO2 in the pulmonary capillaries favor? | The production of oxyhemoglobin. |
| What happens to H+ when oxyhemoglobin is produced in the lungs? | It dissociates from hemoglobin and recombines with bicarbonate to form carbonic acid (H2CO3). |
| During the reverse chloride shift, how do chloride and bicarbonate ions move? | Chloride diffuses out of the RBC as bicarbonate enters. |
| What enzyme converts carbonic acid back into CO2 and H2O in a low PCO2 environment? | Carbonic anhydrase. |
| What happens to the CO2 after it is reformed in the lungs? | It is exhaled. |
| Which two organs are primarily responsible for maintaining blood pH within a constant range? | The lungs and the kidneys. |
| Why is carbonic acid considered a volatile acid? | Because it can be converted into carbon dioxide gas and exhaled, meaning it is regulated by breathing. |
| How are nonvolatile acids (like lactic, fatty, and ketone acids) buffered and regulated? | They are buffered by bicarbonate and regulated by the kidneys via excretion, not by breathing. |
| What is the major buffer in the blood, and how is it classed? | Bicarbonate ion, which is a weak base. |
| Why is buffering excess H+ with bicarbonate not a permanent fix? | Because bicarbonate will eventually run out, meaning the excess H+ is only temporarily hidden in water molecules. |
| How do the kidneys provide a permanent solution for excess H+? | By excreting H+ ions altogether in the urine and producing more bicarbonate. |
| (starred) What causes respiratory acidosis? | Hypoventilation, which causes a rise in CO2 that increases H+ and lowers pH. |
| (starred) What causes metabolic acidosis? | Excessive production of acids or the loss of bicarbonate (such as from diarrhea). |
| (starred) What causes respiratory alkalosis? | Hyperventilation, which "blows off" CO2, causing H+ to decrease as mass action tries to replenish the CO2. |
| (starred) What causes metabolic alkalosis? | Inadequate production of acids, overproduction of bicarbonates, or loss of digestive acids from vomiting. |
| (starred) How is the respiratory component of blood pH measured? | By plasma CO2 levels. |
| (starred) How is the metabolic component of blood pH measured? | By plasma bicarbonate levels. |
| How does the body partially compensate for metabolic acidosis or alkalosis? | Through opposite changes in blood carbonic acid levels via changes in ventilation. |
| How does the body partially compensate for respiratory acidosis or alkalosis? | By increased retention or excretion of bicarbonate in the urine. |
| What condition is occurring if plasma CO2 is normal but plasma HCO3- is low? | Metabolic acidosis (and ventilation will look like hyperventilation to compensate). |
| What condition is occurring if plasma CO2 is normal but plasma HCO3- is high? | Metabolic alkalosis (and ventilation will look like hypoventilation to compensate). |
| What condition is occurring if both plasma CO2 and plasma HCO3- are low? | Respiratory alkalosis caused by hyperventilation. |
| What condition is occurring if both plasma CO2 and plasma HCO3- are high? | Respiratory acidosis caused by hypoventilation. |
| According to the Henderson-Hasselbalch Equation, at what ratio of bicarbonate to CO2 is normal blood pH maintained? | A ratio of 20:1. |
| (bolded) Which type of acid-base imbalance occurs with an abnormal CO2 concentration? (respiratory or metabolic) | Respiratory acidosis or alkalosis. |
| (bolded) Which type of acid-base imbalance occurs with an abnormal bicarbonate concentration? (respiratory or metabolic) | Metabolic acidosis or alkalosis. |
| (starred) what controls the respiratory component of acid-base balance? it can compensate for the metabolic component | ventilation |
| How will a person with metabolic acidosis compensate via ventilation? | They will hyperventilate to "blow off" CO2, which decreases H+ and raises pH. |
| How will a person with metabolic alkalosis compensate via ventilation? | They will hypoventilate to build up CO2, which increases H+ and lowers pH. |
| According to the Law of Mass Action, what happens during hypoventilation? (equation goes in what direction?) | Retained CO2 pushes the equation to the right, making extra H+ and causing respiratory acidosis. |
| According to the Law of Mass Action, what happens during hyperventilation? (equation goes in what direction?) | Lost CO2 pushes the equation to the left, using up H+ and causing respiratory alkalosis. |
| (bolded) What is the deeper, faster breathing produced by exercise to match oxygen utilization and CO2 production called? | Hyperpnea. |
| (emphasized) What two mechanisms control the increase in ventilation during exercise? | Neurogenic and humoral mechanisms. |
| (highlighted) How does sensory nerve activity from exercising muscles stimulate respiration? | Via spinal reflexes or brain stem respiratory centers. |
| (highlighted) Which part of the brain stimulates respiratory centers in anticipation of needing oxygen during exercise? | The cerebral cortex. |
| (highlighted) What do the proposed neurogenic mechanisms help explain regarding the timing of increased ventilation? | They help explain the immediate increase in ventilation at the beginning of exercise. |
| Why does rapid and deep breathing continue after exercise despite PO2, PCO2, and pH returning to resting ranges? | Due to humoral (chemical) factors. |
| What are two theories for why deep breathing continues after exercise when blood samples show normal values? | There may be regional PCO2 and pH differences at the chemoreceptors, or cyclic variations affecting chemoreceptors that blood samples miss. |
| What is the primary difference between hyperpnea and hyperventilation? | Both involve faster, deeper breathing, but only hyperventilation involves a decrease in arterial blood PCO2. |
| Are there consistent or significant changes in arterial blood gases and pH during the first several minutes of moderate and heavy exercise? | No, the body compensates very well. |
| Which arterial blood measurement actually decreases during more prolonged exercise? | PCO2. |
| What type of respiration occurs at the beginning of exercise when ventilation cannot deliver enough O2? | Anaerobic respiration. |
| What process will muscles revert to if heavy exercise continues after the initial adjustment period? | Lactic acid fermentation. |
| (bolded) What is the term for the maximum rate of oxygen consumption attained before lactic acid levels rise? | lactate threshold |
| (bolded) At what percentage of maximum oxygen uptake does the lactate threshold typically occur? | When 50 to 70% of maximum oxygen uptake is reached. |
| (bolded) Is the lactate threshold due to limitations in the cardiovascular system or the muscles? | It is due to aerobic limitations of the muscles, not the cardiovascular system. |
| (bolded) How does endurance exercise training affect the lactate threshold? | It raises the lactate threshold by increasing mitochondria and Krebs cycle enzymes in the muscles. |
| Why is ventilation increased during exercise? | To match the metabolic rate (increased muscle oxygen consumption and CO2 production). |
| (bolded in red) Why do measurements of blood gases show little change during exercise? | Because ventilation successfully increases to match the increased metabolic demands. |
| (bolded in red) Does total O2 content and PO2 increase during exercise to deliver more oxygen to muscles? | No, oxygen delivery is increased even though total O2 content and PO2 do not increase. |
| (bolded in red) Why is oxygen extraction by muscles increased during exercise? | Increased oxygen consumption lowers tissue PO2, and increased tissue temperature lowers hemoglobin's affinity for oxygen, causing more unloading. |
| (bolded in red) How does venous blood oxygen saturation during exercise compare to resting levels? | Venous blood during exercise contains a lower oxyhemoglobin saturation than at rest. |
| What immediate physiological response occurs when peripheral chemoreceptors detect a drop in arterial oxygen at high altitudes? | Hyperventilation. |
| What acid-base imbalance is initially caused by hyperventilating at high altitudes? | Respiratory alkalosis. |
| How does acute respiratory alkalosis affect the oxyhemoglobin dissociation curve? | It causes a left shift, meaning hemoglobin has a higher affinity for oxygen in the lungs. |
| What molecule do red blood cells produce within a day or two at high altitude to shift the dissociation curve back to the right? | 2,3-BPG (2,3-bisphosphoglycerate). |
| How do the kidneys help correct respiratory alkalosis at high altitudes? | By intentionally excreting bicarbonate ions (HCO3-) in the urine. |
| What is the primary benefit of the kidneys excreting bicarbonate at high altitudes? | It brings blood pH back down to normal, which prevents the brain from slowing down the respiratory rate. |
| What hormone do the kidneys release in response to hypoxia-inducible factor 1 (HIF-1)? | Erythropoietin (EPO). |
| What does Erythropoietin (EPO) stimulate? | Red blood cell production (erythropoiesis) in the bone marrow, which increases hematocrit. |
| What is Hypoxic Pulmonary Vasoconstriction (HPV) at high altitudes? | A systemic constriction of pulmonary arterioles in response to low oxygen. |
| What is a potential long-term risk of systemic Hypoxic Pulmonary Vasoconstriction? | Pulmonary hypertension and right ventricular hypertrophy. |
| What factor do tissues secrete to sprout new capillaries and shorten the oxygen diffusion distance? | Vascular Endothelial Growth Factor (VEGF). |
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