Bio 1006: Chapter 48- Respiration System
Bio 1006: Chapter 48- Respiration System BIOL 1006
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This 4 page Class Notes was uploaded by Gina Nam on Tuesday March 29, 2016. The Class Notes belongs to BIOL 1006 at Virginia Polytechnic Institute and State University taught by Dr. Denbow in Spring 2016. Since its upload, it has received 23 views. For similar materials see General Biology in Biology at Virginia Polytechnic Institute and State University.
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Date Created: 03/29/16
Chapter 48: The Respiratory System GAS EXCHANGE ACROSS RESPIRATORY SURFACES Plasma membranes must be surrounded by water o So external environment in gas exchange is always aqueous o Gas diffuses through a thin aqueous membrane lining respiratory tract (lined by epithelial cells) Passive diffusion process o Driven by the differences in O an2 CO 2 on both sides of the membranes Fick’s Law of Diffusion o Rate of diffusion between two regions DA∆ p o R= d R: rate of diffusion ∆p: pressure difference A: area (where the diffusion occurs) d: distance o evolutionary change optimized the rate of diffusion Unicellular vs. Multicellular Unicellular: gases diffuse directly into the organism Multicellular: system adaptations GILLS, CUTANEOUS RESPIRATION, AND TRACHEAL SYSTEMS External gills o Found in immature fish and amphibians o Disadvantages: constant contact with freshwater and easily damaged Gills in Bony Fish o Housed between the mouth (buccal) cavity and the opercular cavities o Respiration in bony fish: water goes into buccal cavity, through the gills, and out gill cover (open operculum) Gill arch (found on the side of the fish’s head) is composed of two rows of gill filaments which contains a thin membrane plates clamellae o Gas exchange system: as the blood in the direction of the current flow, the blood pressure gets colder; vice versa as the blood moves with the blood flow, blood pressure get warmer Counter current flow Maximizes oxygenation of the blood LUNGS Gills were replaced with lungs in terrestrial animals o Air was less supportive than water Lamella lack support and if collapsed the fish suffocates o Water evaporates Air is rarely saturated with water vapor o Gills work in an oneway flow system vs atwoway flow system in terrestrial animals o Lungs minimize water evaporation through branched tubular passage Breathing air takes advantage of partial pressures of gases o Air is exerted downwards Different atmospheric pressures affect the partial pressures of gases in the air E.g. atmospheric pressures of 380mm Hg only has half the amount of O2 available than at sea level (760mm Hg) Amphibians vs. Reptiles o Amphibians breathe by positive pressure breathing pushing air into the lungs Similar to mouthtomouth resuscitation o Reptiles breathe by negative pressure breathing “pulling in” air into the lungs Expands rib cage by muscle contraction Mammalian lungs have greatly increased surface area o Lungs are packed with aveoli sites for gas exchange Provides a larger surface area for gas exchange o Inhaled air passes through the trachea which is delivered to the bronchus then to the lungs to reach the aveoli o Air passage: pharynx, larynx, glottis, trachea, bronchus, alveoli Birds o Parabronchi air vessels; gas exchange occurs here o Unidirectional flow Air inhaled the first cycle is not exhaled until the second cycle o Posterior and Anterior air sacs The air moves into thposterior sac and then moves into or exhaled into the lungs (Cycle 1) The air is drawn from the lungs and into tanterior sac then the air moves out the trachea and is expelled (Cycle 2) At the same time new air is taken into the posterior sac and into the lungs, starting a new cycle STRUCTURES, MECHANISMS, AND CONTROL OF VENTILATION IN MAMMALS Lung structure o Visceral pleural membrane thin membrane that covers the outside of each lung o Parietal pleural membrane lines the inner wall of the thoracic cavity o Pleural cavity the space filled with a small amount of fluid between the two membranes; allows lungs to expand o Diaphragm andexternal intercostal muscles contract to increase thoracic volume Intercostal muscles expand the rib cage Diaphragm expands the volume of the lungs o Lungs and thorax have a degree of elasticity Allows to expand and recoil Ventilation under nervous system control o Respiratory control central Located in the medulla oblongata Breathe diaphragm and external intercostal muscles contraction ) isinitiated by the neurons originating from here Exhalation occurs when neurons stop sending impulses o Neurons are sensitive to changes in partial pressures of CO2 n the blood Increase in C2 levels lead to increase in carbonic acid production Decrease pH o Stimulates chemosensitive neurons in the aortic and carotid bodies o Sends impulse to respiratory control central o Increase breathing TRANSPORT OF GASES IN BODY FLUIDS Hemoglobin o Consists of four polypeptide chains Each chain can bind to a molecule of2O o At rest, onefifth of the oxygen is unloaded in the tissues Fourfifths of the oxygen is left in the blooreserve when body exerts energy o Affinity for O 2isaffected by pH and temperature Lower pH causes hemoglobin to release oxygen more readily Primarily occurs inside red blood cells + Bohr effect or Bohr shift result of H binding to hemoglobin Increase in temperature the blood unloads a higher percentage of O 2 o Transportation of CO 2 Carbonic anhydrase combines CO to H O2to for2 H CO 2 3 + H 2O di3 ssociates into H and HCO 3 H binds to deoxyhemoglobin When the blood passes through the pulmonary capillaries, the reaction is reversed Production of CO ga2
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