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Chap 42 Circulation and Gas Exchange Gastrovascular cavities and body walls only two layers thick allow for easy distribution of nutrients and gas exchange • In insects, other arthropods, and most mollusks, blood bathes organs directly in an open circulatory system. • There is no distinction between blood and interstitial fluid, collectively called hemolymph. • One or more hearts pump the hemolymph into interconnected sinuses surrounding the organs, allowing exchange between hemolymph and body cells. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 42.2a Blood empties into sinus Blood always stays in a blood vessel more efficient • Arteries carry blood to capillaries – The sites of chemical exchange between the blood and interstitial fluid • Veins – Return blood from capillaries to the heart Blood going through body under low pressure The pulmonary and systemic circuits are not completely separated Completely separation ensures oxygenated blood going to systemic circuit under high pressure • Vertebrate circulatory systems AMPHIBIANS REPTILES (EXCEPT BIRDS) MAMMALS AND BIRDS Lung and skin capillaries Lung capillaries Lung capillaries FISHES Gill capillaries Artery Pulmocutaneous circuit Gill circulation Heart: ventricle (V) A Atrium (A) Systemic Vein circulation Systemic capillaries Right systemic aorta Pulmonary circuit A A V Right V Left Right Systemic circuit Systemic capillaries Figure 42.4 Pulmonary circuit Left Systemic V aorta Left A Systemic capillaries A V Right A V Left Systemic circuit Systemic capillaries • A powerful four-chambered heart – Was an essential adaptation of the endothermic way of life characteristic of mammals and birds Mammalian Circulation: The Pathway • Heart valves – Dictate a one-way flow of blood through the heart Circulation movie 1. Pearson circulatory Lab Turn in Lab Quiz tommorrow 2. Heart Review Do the following review Print out quiz to turn in http://www.midpac.edu/~biology/Intro%20Biology/PH%20Biolo gy%20Lab%20Simulations/cardio1/intro.html • A cardiac cycle is one complete sequence of pumping, as the heart contracts, and filling, as it relaxes and its chambers fill with blood. – The contraction phase is called systole, and the relaxation phase is called diastole. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings ECG Video • All blood vessels – Are built of similar tissues – Have three similar layers Artery Vein Basement membrane Endothelium 100 µm Valve Endothelium Smooth muscle Connective tissue Endothelium Capillary Smooth muscle Connective tissue Artery Vein Venule Figure 42.9 Arteriole Single wall capillaries ideal for allowing diffusion through and between endothelial cells Thicker and more elastic • The apparent contradiction between observations and the law of continuity can be resolved when we recognize that the total crosssectional area of capillaries determines flow rate in each. Fig. 42.10 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Speed of blood decreases in the capillaries because ? What are two reasons why the pressure decreases? • Fluids exert a force called hydrostatic pressure against surfaces they contact, and it is that pressure that drives fluids through pipes. – Fluids always flow from areas of high pressure to areas of lower pressure. – Blood pressure, the hydrostatic force that blood exerts against vessel walls, is much greater in arteries than in veins and is highest in arteries when the heart contracts during ventricular systole, creating the systolic pressure. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • When you take your pulse by placing your fingers on your wrist, you can feel an artery bulge with each heartbeat. – The surge of pressure is partly due to the narrow openings of arterioles impeding the exit of blood from the arteries, the peripheral resistance. – Thus, when the heart contracts, blood enters the arteries faster than it can leave, and the vessels stretch from the pressure. – The elastic walls of the arteries snap back during diastole, but the heart contracts again before enough blood has flowed into the arterioles to completely relieve pressure in the arteries, the diastolic pressure. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • A sphygmomanometer, an inflatable cuff attached to a pressure gauge, measures blood pressure fluctuations in the brachial artery of the arm over the cardiac cycle. – The arterial blood pressure of a healthy human oscillates between about 120 mm Hg at systole and 70 mm Hg at diastole. Fig. 42.11 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Smooth muscles and hormones can regulate the amount of blood in capillaries only 5-10% have blood in them at any one time The osmotic pressure due to the proteins in the blood plasma allow for about 85% of the fluids to reenter the capillaries - the remaining 15% that remain in the interstitual fluid returns via the lymph system • The difference between blood pressure and osmotic pressure – Drives fluids out of capillaries at the arteriole end and into capillaries at the venule end Tissue cell Capillary Red blood cell Net fluid movement out Net fluid movement in 15 m At the arterial end of a capillary, blood pressure is greater than osmotic pressure, and fluid flows out of the capillary into the interstitial fluid. At the venule end of a capillary, blood pressure is less than osmotic pressure, and fluid flows from the interstitial fluid into the capillary. Direction of blood flow Blood pressure Osmotic pressure Pressure Capillary INTERSTITIAL FLUID Inward flow Outward flow Arterial end of capillary Figure 42.14 Venule end If the hydrostatic pressure increases there is an increases OUTFLOW of fluids into the cells If hydrostatic pressure decreases there will be an Net INFLOW of material from the cells Decreasing the plasma proteins lowers the osmotic pressure of the blood causing more fluid to be pushed outward 8. The lymphatic system returns fluid to the blood and aids in body defense • Fluids and some blood proteins that leak from the capillaries into the interstitial fluid are returned to the blood via the lymphatic system. – Fluid enters this system by diffusing into tiny lymph capillaries intermingled among capillaries of the cardiovascular system. – Once inside the lymphatic system, the fluid is called lymph, with a composition similar to the interstitial fluid. – The lymphatic system drains into the circulatory system near the junction of the venae cavae with the right atrium. • Lymph vessels, like veins, have valves that prevent the backflow of fluid toward the capillaries. – Rhythmic contraction of the vessel walls help draw fluid into lymphatic capillaries. – Also like veins, lymph vessels depend mainly on the movement of skeletal muscle to squeeze fluid toward the heart. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • Along a lymph vessels are organs called lymph nodes. – The lymph nodes filter the lymph and attack viruses and bacteria. – Inside a lymph node is a honeycomb of connective tissue with spaces filled with white blood cells specialized for defense. • When the body is fighting an infection, these cells multiply, and the lymph nodes become swollen. • In addition to defending against infection and maintaining the volume and protein concentration of the blood, the lymphatic system transports fats from the digestive tract to the circulatory system. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Filarial worms can block lymph, causing a build of up of fluid Elephantiasis Blood Composition and Function • Blood consists of several kinds of cells – Suspended in a liquid matrix called plasma • The cellular elements – Occupy about 45% of the volume of blood Plasma • Blood plasma is about 90% water • Among its many solutes are – Inorganic salts in the form of dissolved ions, sometimes referred to as electrolytes Found in bone marrow - ribs, vertebrae, breastbone, pelvis Low O2 triggers erythropoeitin At high altitudes more red blood cells are produced Preadapted for high altitudes Ex: thromboplastin Cascade effect: each step as as an enzyme catalyzing many more reactions at each step each level results in many more molecules A blood clot or thrombus can result in a thromboembolus in the brain it could result in a stroke in the heart it could result in a myocardial infarction or heart attack Fatty deposits result in Atherosclerosis -more likely to catch thrombus LDL may increase plaque deposits - HDL may decrease • Hypertension (high blood pressure) promotes atherosclerosis and increases the risk of heart disease and stroke. – According to one hypothesis, high blood pressure causes chronic damage to the endothelium that lines arteries, promoting plaque formation. – Hypertension is simple to diagnose and can usually be controlled by diet, exercise, medication, or a combination of these. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings • To some extent, the tendency to develop hypertension and atherosclerosis is inherited. • Nongenetic factors include smoking, lack of exercise, a diet rich in animal fat, and abnormally high levels of cholesterol in the blood. • One measure of an individual’s cardiovascular health or risk of arterial plaques can be gauged by the ratio of low-density lipoproteins (LDLs) to high-density lipoproteins (HDLs) in the blood. – LDL is associated with depositing of cholesterol in arterial plaques. – HDL may reduce cholesterol deposition. 4 Basic Needs of Gas Exchange 1. A thin, moist respiratory surface of adequate dimension 2. A method of transport of gases to the inner cells Gas exchange is needed for cell respiration 3. A means of protecting the fragile respiratory surface 4. A way to keep the surface moist while limiting water loss • The part of an animal where gases are exchanged with the environment is the respiratory surface. – Movements of CO2 and O2 across the respiratory surface occurs entirely by diffusion. – The rate of diffusion is proportional to the surface area across which diffusion occurs, and inversely proportional to the square of the distance through which molecules must move. – Therefore, respiratory surfaces tend to be thin and have large areas, maximizing the rate of gas exchange. – In addition, the respiratory surface of terrestrial and aquatic animals are moist to maintain the cell membranes and thus gases must first dissolve in water. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Large SA/Vol ratio Body surface used in gas exchange Evaginatation increases surface area gills Lungs-invaginations + circulatory system Invaginations such as trachea 2. Gills are respiratory adaptation of most aquatic animals • Gills are outfoldings of the body surface that are suspended in water. – The total surface area of gills is often much greater than that of the rest of the body. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Polychaete worm • The feathery gills projecting from a salmon – Are an example of a specialized exchange system found in animals Figure 42.1 Copyright © 2005 Pearson Education, Inc. publishing as Benjamin Cummings Water is moving countercurrent to blood flow Blood Flow • This flow pattern is countercurrent exchange. – As blood moves anteriorly in a gill capillary, it becomes more and more loaded with oxygen, but it simultaneously encounters water with even higher oxygen concentrations because it is just beginning its passage over the gills. – All along the gill capillary, there is a diffusion gradient favoring the transfer of oxygen from water to blood. Fig. 42.20 Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Tracheal systems and lungs are respiratory adaptations of terrestrial animals • As a respiratory medium, air has many advantages over water. – Air has a much higher concentration of oxygen. – Also, since O2 and CO2 diffuse much faster in air than in water, respiratory surfaces exposed to air do not have to be ventilated as thoroughly as gills. – When a terrestrial animal does ventilate, less energy is needed because air is far lighter and much easier to pump than water and much less volume needs to be breathed to obtain an equal amount of O2. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Tracheal systems in insects allow for gas to be transported directly to most cells -no need for hemoglobin to transport oxygen Spiracles control the opening the trachea Fig. 42.22 • The tracheal tubes – Supply O2 directly to body cells Body cell Air sac Tracheole Trachea Air Tracheoles Mitochondria Body wall Myofibrils (b) This micrograph shows cross sections of tracheoles in a tiny piece of insect flight muscle (TEM). Each of the numerous mitochondria in the muscle cells lies within about 5 µm of a tracheole. Figure 42.22b 2.5 µm • Unlike branching tracheal systems, lungs are restricted to one location. – Because the respiratory surface of the lung is not in direct contact with all other parts of the body, the circulatory system transports gases between the lungs and the rest of the body. – Lungs have a dense net of capillaries just under the epithelium that forms the respiratory surface. – Lungs have evolved in spiders, terrestrial snails, and vertebrates. Book lung found in spiders subdivisions increase surface area Increasing the subdivision of the lungs increases the surface area for gas exchange Mammalian Respiratory Systems: A Closer Look • A system of branching ducts » Conveys air to theBranch lungs Branch from the pulmonary artery (oxygen-poor blood) from the pulmonary vein (oxygen-rich blood) Terminal bronchiole Nasal cavity Pharynx Left lung Alveoli 50 µm 50 µm Larynx Esophagus Trachea Right lung Bronchus Bronchiole Diaphragm Heart SEM Figure 42.23 Colorized SEM How an Amphibian Breathes • An amphibian such as a frog – Ventilates its lungs by positive pressure breathing, which forces air down the trachea How a Mammal Breathes • Mammals ventilate their lungs – By negative pressure breathing, which pulls air into the lungs Rib cage expands as rib muscles contract Air inhaled Rib cage gets smaller as rib muscles relax Air exhaled Lung Diaphragm INHALATION Diaphragm contracts (moves down) Figure 42.24 EXHALATION Diaphragm relaxes (moves up) Higher air pressure forces air in Lower pressure Negative pressure breathing Tidal volume is a normal breath The volume increases by the diaphragm moving down and the rib cage moving up and out Vital capacity is the max volume of a breath Residual volume is left over after exhalation - old air that will be mixed in with the new • The volume of air an animal inhales and exhales with each breath is called tidal volume. – It averages about 500 mL in resting humans. • The maximum tidal volume during forced breathing is the vital capacity, which is about 3.4 L and 4.8 L for college-age females and males, respectively. – The lungs hold more air than the vital capacity, but some air remains in the lungs, the residual volume, because the alveoli do not completely collapse. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings How a Bird Breathes • Besides lungs, bird have eight or nine air sacs – That function as bellows that keep air flowing through the lungs Air Air Anterior air sacs Trachea Posterior air sacs Lungs Lungs Air tubes (parabronchi) in lung INHALATION Air sacs fill EXHALATION Air sacs empty; lungs fill Figure 42.25 Parabronchi allow for one way flow of air through lungs 1 mm • This system completely exchanges the air in the lungs with every breath. – Therefore, the maximum lung oxygen concentrations are higher in birds than in mammals. – Partly because of this efficiency advantage, birds perform much better than mammals at high altitude. • For example, while human mountaineers experience tremendous difficulty obtaining oxygen when climbing the Earth’s highest peaks, several species of birds easily fly over the same mountains during migration. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings High CO2 levels increase the acidity of blood and cerebrospinal fluid triggering the medulla to increase the depth and rate of breathing Low O2 levels trigger sensors in the Carotid arteries and the Aorta to trigger the medulla • Our breathing control centers are located in two brain regions, the medulla oblongata and the pons. – Aided by the control center in the pons, the medulla’s center sets basic breathing rhythm, triggering contraction of the diaphragm and rib muscles. – A negative-feedback mechanism via stretch receptors prevents our lungs from overexpanding by inhibiting the breathing center in the medulla. • Concept 42.7: Respiratory pigments bind and transport gases • The metabolic demands of many organisms – Require that the blood transport large quantities of O2 and CO2 The Role of Partial Pressure Gradients • Gases diffuse down pressure gradients – In the lungs and other organs • Diffusion of a gas – Depends on differences in a quantity called partial pressure Partial pressure of O2 is 760 mm Hg X 21%= 160 Oxygen Transport • The respiratory pigment of almost all vertebrates – Is the protein hemoglobin, contained in the erythrocytes • Like all respiratory pigments – Hemoglobin must reversibly bind O2, loading O2 in the lungs and unloading it in other parts of the body One molecule of hemoglobin has 4 prosthetic heme groups, allowing it to bind to 4 O2 molecules Cooperativity Heme group -the binding of one O2 allows the next O2 to bind easier Iron atom O2 loaded in lungs O2 unloaded In tissues Figure 42.28 Polypeptide chain O2 O2 • Loading and unloading of O2 – Depend on cooperation between the subunits of the hemoglobin molecule • The binding of O2 to one subunit induces the other subunits to bind O2 with more affinity • Cooperative O2 binding and release – Is evident in the dissociation curve for hemoglobin • A drop in pH – Lowers the affinity of hemoglobin for O2 H+ from carbonic acid can act as a negative modulator for hemoglobin, causing it to release more O2 Bohr shifts curve to the right At 40 mm HG pH 7.2= 60 mm Hg pH 7.4= 70 mm Hg • As with all proteins, hemoglobin’s conformation is sensitive to a variety of factors. • For example, a drop in pH lowers the affinity of hemoglobin for O2, an effect called the Bohr shift. • Because CO2 reacts with water to form carbonic acid, an active tissue will lower the pH of its surroundings and induce hemoglobin to release more oxygen. Fig. 42.28b Higher temps right shift curve making it easier to dump Oxygen Animals with a high metabolic rate have a right shifted curve Hb acts as a buffer in picking up H+ Most CO2 travels in the plasma as a bicarbonate ion Bet You Didn't Know They Treat Meat With Carbon Monoxide To Fool You. Hemoglobin has a great affinity to CO – it binds and turns red, giving even old meat the appearance of freshness. If you breath in CO, hemoglobin will not release it and not be able to transport O2. Deep-diving air-breathers stockpile oxygen and deplete it slowly • When an air-breathing animal swims underwater, it lacks access to the normal respiratory medium. – Most humans can only hold their breath for 2 to 3 minutes and swim to depths of 20 m or so. In comparison with diving mammals, humans are poorly adapted to life in the water. In 2002, free-diving champion Mandy-Rae Cruikshank set a women’s world record for static apnea of 6 minutes 13 seconds (the men’s record, set in 2001 by Scott Campbell, is 6 minutes 45 seconds) – However, a variety of seals, sea turtles, and whales can stay submerged for much longer times and reach much greater depths. Weddell Seal Dive Adaptations • Stores more O2 in its blood • Has more blood, has larger spleen for storage of blood • Has higher amount of O2 storing protein called myoglobin in muscles • Heart rate(125>10) and O2 consumption rate decrease • Blood to muscles restricted • Blood routed to vital organs brain, eyes /peripheral vasoconstriction. A school of salema attempts to outmaneuver a hungry sea lion near the Galápagos Islands by circling to confuse the predator. Galápagos sea lions dive down some 120 feet (37 meters) on average to feed, returning to the surface after a minute or two to breathe. Pearson Daphnia Temp Lab Turn in Lab Quiz 2 tomorrow