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Circulation and Gas Exchange CIRCULATIONTransport systems (circulation) linked with gas exchange (respiration) Diffusion of gases only rapid across small distances Basic: Cells in direct contact with environment, Ex. Sponges Gastrovascular Cavity: For digestion & distribute substances, Ex. jellies, flatworms Circulatory System: Moves fluid to tissues & cells for exchange, Ex. larger animals Circulatory System = Blood + Vessels + Heart Open circulatory system: blood bathes organs directly• Blood + lymph = hemolymph• Heart pumps hemolymph into sinuses• Ex. arthropods, mollusks Closed circulatory system: blood contained in vessels & pumped around body• Blood and fluid separate• Ex. annelids, cephalopods, vertebrates Types of Blood VesselsArteries: blood away from heart, high pressure, thick/strong walls, pulseCapillaries: connect arteries/veins, single-cell thick walls, exchange of O2/CO2Veins: blood back to heart, low pressure, thin-walled and large diameter, valves prevent backflow Blood enters through an atrium and is pumped out through a ventricleFish = single circulation pathway, 2 chambersDouble circulation: amphibians, reptiles, mammals Cardiac cycleSystole: contraction or pumping phaseDiastole: relaxation or filling phaseHeart rate: # beats/minute (72 bpm resting)Stroke volume: amount of blood pumped by L. ventricle during contraction (~70 ml) Valves: prevent backflow of bloodThe atrioventricular (AV) valves (tricuspid, bicuspid) separate each atrium and ventricleThe semilunar valves control blood flow to the aorta and the pulmonary artery“Lub-dup” sound = blood against closed AV valves (lub) / the semilunar (dup) valvesHeart murmur: backflow of blood through a defective valve Sinoatrial (SA) node: pacemaker of heart, in right atriumThe pacemaker is regulated by two portions of the nervous system: the sympathetic and parasympathetic divisionsThe sympathetic division speeds up the pacemakerThe parasympathetic division slows down the pacemakerThe pacemaker is also regulated by hormones (epinephrine) and temperature Blood PressureBP = systolic/diastolic pressureSystolic: heart contractsDiastolic: heart relaxedNormal: 120/70 Pulse: rhythmic bulging of artery walls with each heartbeatLymphatic System: returns lost fluid and proteins to blood as lymphLymph Nodes: filter lymph, house WBC’sImmune system role BloodPlasma (55%) – water, ions, proteins, gases, nutrients, wastes, hormonesCells (45%) – RBC, WBC, plateletsDevelop from stem cells in bone marrowRed blood cells (erythrocytes): O2 transport via hemoglobinWhite blood cells (leukocytes): fight infectionPlatelets (cell fragments): blood clotting Cardiovascular DiseaseAtherosclerosis: buildup of plaque deposits within arteriesHeart attack (myocardial infarction): blockage of one or more coronary arteriesStroke: rupture or blockage of arteries in the headHypertension: high blood pressure; promotes atherosclerosis and increases the risk of heart attack and stroke GAS EXCHANGERespiration• Gas exchange supplies O2 for cellular respiration and disposes of CO2• Partial pressure = pressure exerted by a particular gas in a mixture of gases• Gases always diffuse from higher partial pressure à lower partial pressure • Respiratory media: O2 in air or water• Respiratory surface: body wall, skin, gills, tracheae, lungs• Characteristics:– Moist– Large surface area-to-volume ratio– Larger animals: associated with vascular system Examples: Fish gills: absorb O2 through countercurrent exchange (blood flows opposite of water) Tracheal systems in insects Respiratory system in birds (lungs + air sacs) Mammalian respiratory system Mammalian respiratory system:Pathway of O2• Nose/mouth: filtered, warmed, humidified• Pharynx• Larynx: contains vocal cords• Trachea: windpipe; lined with cartilage• Bronchi: branches to lungs• Bronchioles• Alveoli: air sacs for gas exchange• Mucus: traps particles• Cilia: sweeps particles up to pharynxDiaphragm: dome-shaped muscle separating thoracic/abdominal cavities Control of Breathing in Humans• Control center = medulla oblongata• Responds to pH changes in blood• High CO2 à carbonic acid forms à lowers pH• Sensors in the aorta and carotid arteries Adaptations for gas exchange• Hemoglobin: respiratory pigment in vertebrates– 4 subunits, each with heme group with iron (Fe)– Can carry 4 molecules of O2– Bohr shift: O2 dissociates from hemoglobin when blood pH is low – Arthropods, mollusks: blue hemocyanin pigment contains copper (Cu) How CO2 is transportedBicarbonate ions (70%)Hemoglobin (23%)Dissolved in plasma (7%) Respiratory Adaptations of Diving Mammals• Diving mammals have evolutionary adaptations that allow them to perform extraordinary feats– For example, Weddell seals in Antarctica can remain underwater for 20 minutes to an hour– For example, elephant seals can dive to 1,500 m and remain underwater for 2 hours• High blood to body volume ratio• Stockpile O2 and deplete it slowly• Store oxygen in their muscles in myoglobin proteins Respiratory Disorders• Asthma: airways constricted• Bronchitis: bronchi swollen and clogged• Pneumonia: inflammation of lung caused by infection• Tuberculosis (TB): infectious disease caused by M. tuberculosis• Emphysema: lose elasticity of lung tissue• Lung Cancer: abnormal cell growth in lungs
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