FSU BSC 2086 - Lesson 2: Special Senses

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Lesson 14: Respiratory System – Gas ExchangeExplain the difference between external and internal respirationExternal Respiration:Includes all processes involved in exchanging O2 and Co2 with the ENVIRONMENTInternal Respiration:Result of Cellular RespirationInvolves the uptake of O2 and production of CO2 within individual CELLS (mitochondria)What are the three processes to external respiration?1. Pulmonary Ventilation“Breathing”Physical movement of air in and out of respiratory tractProvides alveolar ventilation (air movement into/out of alveoli)Movement of Air:Atmospheric Pressure: the weight of airCompresses our bodies and everything around usHas several important physiological effects2. Gas DiffusionAcross membranes and capillaries3. Transport of O2 and CO2Between alveolar capillariesBetween capillary beds in other tissuesAbnormal External Respiration is DangerousHypoxia: low tissue oxygen levelsAnoxia: complete lack of oxygen  quickly kills cellsDescribe the process of inspiration and expiration. Which muscles are involved? How do those processes affect the intrapulmonary pressure inside the lungs?Inspiration:InhalationElevation of the rib cage and contraction of the diaphragm increase the size of the thoracic cavityPressure within the thoracic cavity decreases, and air flows into the lungsExpiration:ExhalationWhen the rib cage returns to its original position and the diaphragm relaxes, the volume of the thoracic cavity decreases. Pressure rises, and air moves out of the lungsExplain the difference between intrapulmonary and intrapleural pressureIntrapulmonary Pressure:“Intraalveolar Pressure”Air pressure inside the alveoliRelative to atmospheric pressureIn relaxed breathing, the difference between atmospheric pressure and intrapulmonary pressure is smallAbout -1 mmHg on inhalation or +1 mmHg on exhalationMaximum Intrapulmonary Pressure:Maximum straining, a dangerous activity, can increase range from -30 mmHg to + 100 mmHgIf too high, can cause alveolar rupture or herniaIntrapleural Pressure:Pressure in space BETWEEN parietal and visceral pleuraAverage: - 4 mmHgMaximum: -18 mmHg (during powerful inhalation)Remains below atmospheric pressure throughout respiratory cycleCaused by elastic recoil of lung tissue pulling on chest wallNOTE: compared to intrapulmonary pressure, the intrapleural pressure is ALWAYS negative in a normal functioning lungDescribe some disorders associated with the lungsPneumothorax:Allows air into pleural cavityBreaks the fluid bond between the pleuraeFrom ruptured alveoli through visceral pleura or injury that punctures parietal pleuraAtelectasis:“Collapsed Lung”Result of pneumothoraxEmphysema:Alveolar tissue damageCauses high complianceRespiratory Distress Syndrome:Causes low complianceExplain how compliance can affect lung volumeCompliance:An indicator of expandabilityLow Compliance requires GREATER force to fill lungsHigh Compliance requires LESS force to fill lungsFactors that Affect Compliance:1. Connective Tissue Structure of the LungsEmphysema2. Level of Surfactant ProductionRespiratory Distress Syndrome causes low compliance3. Mobility of the Thoracic Cage4. Arthritis/Skeletal Disorders Reduce ComplianceDescribe the various lung volumesTotal Lung Volume:Divided into a series of volumes and capacities useful in diagnosing problemsFour Pulmonary Volumes:1. Resting Tidal Volume (Vt):In a normal respiratory cycle2. Expiratory Reserve Volume (ERV):After a normal exhalation3. Residual Volume:After maximal exhalation4. Inspiratory Reserve Volume (IRV):After a normal inspirationExplain Boyle’s Law, Dalton’s Law, and Henry’s LawBoyle’s Law:Defines the relationship between gas pressure and volumeP = 1/VIn a contained gas:External pressure forces molecules closer togetherMovement of gas molecules exerts pressure on containerDecrease volume  increase pressureIncrease volume  decrease pressureDalton’s Law:Partial PressuresEach gas contributes to the total pressure in proportion to its number of moleculesHenry’s Law:When gas under pressure comes in contact with liquid:Gas dissolves in liquid until equilibrium is reachedAt a Given TemperatureAmount of gas in solution is proportional to partial pressure of that gasThe actual amount of gas in solution (at given partial pressure and temperature)Depends on solubility of that gas in that particular liquidExplain why gas exchange is efficient in the lungsGas Exchange occurs between blood and alveolar air, across the respiratory membraneDepends On:Partial Pressures of the GasesDiffusion of molecules between gas and liquidDiffusion occurs in response to concentration gradientsFive Reasons for Efficiency of Gas Exchange:1. Substantial Differences in Partial Pressure Across Respiratory Membrane2. Distances Involved in Gas Exchange are Short3. O2 and CO2 are lipid soluble4. Total Surface Area is Large5. Blood flow and airflow are coordinatedExplain the role of hemoglobin and red blood cells in gas exchangeRed Blood Cells:Transport O2 to, and CO2 from, peripheral tissuesRemove O2 and CO2 from plasma, allowing gases to diffuse into bloodHemoglobin:O2 binds to iron ions in hemoglobin (Hb) molecules forming oxyhemoglobin (HbO2)Reversible reactionEach RBC has about 280 million Hb MoleculesEach Hb molecule binds 4 oxygen moleculesThat’s 1.1 billion O2 molecules transported in a single red blood cellDescribe the Bohr effect and how that affects oxygen transportBohr Effect:The result of pH on hemoglobin-saturation curveCaused by Co2Co2 diffuses into RBCCarbonic anhydrase (enzyme) catalyzes reaction with H2OProduces carbonic acid (H2CO3)Dissociates into hydrogen ion (H+) and bicarbonate ion (HCO3-)Hydrogen ions diffuse out of RBC  lowers pHExplain how carbon dioxide is carried in bloodCarbon Dioxide (CO2) is generated as a by-product of aerobic metabolism (cellular respiration)Carbon Dioxide Transport is generated as a by-produce of aerobic metabolism (cellular respiration)CO2 in Bloodstream can be Carried Three Ways:1. Converted to Carbonic Acid70% of CO2 is transported as carbonic acidProduced inside RBC by carbonic anhydraseCarbonic acid dissociates into H+ and bicarbonate (HCO3-)Most of the hydrogen ions bind to hemoglobin (HbH+)Act as a pH bufferBicarbonate ions:Move into plasma by an exchange mechanism (chloride shift) that takes in Cl- ions without using ATP2. Bound to Hemoglobin within RBCs23% bound to amino groups of globular protein in Hb Molecule (carbaminohemoglobin)3. Dissolved


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FSU BSC 2086 - Lesson 2: Special Senses

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