Lecture: chapter 42: circulation and gas exchange 4/12/12 Overview Gills are an ex of a specialized exchange system in animals Gastrovascular cavity This cavity functions in both digestion and distribution of substances throughout the body. Open and closed circulatory system More complex animals have either open or closed circulatory systems Both systems have 3 basic components A circulatory fluid (blood or hemolymph) A set of tubes ( blood vessels) A muscular pump (the heart) Single circulation Fishes figure Double circulation Amphibians, reptiles (birds) and mammals Figure Mammalian circulation Figure 42.6 The mammalian heart A closer look at the mammalian heart provides a better understanding of how double circulation works. The cardiac cycle The heart contracts and relaxes in a rhythmic cycle called the cardiac cycle. The contracting, or pumping, phase is called systole  The relaxation, or filling, phase is called diastole Impulses that ravel during the cardiac cycle can be recorded as a electrocardiogram (ECG or EKG). The pacemaker is influenced by nerves, hormones, body temp, and exercise. Blood pressure is the hydrostatic pressure that the blood exerts against the wall of a vessel. In rigid vessels blood pressure is maintained; less rigid vessels deform and blood pressure is lost. Blood pressure and gravity Blood pressure is generally measured for an artery in the arm at the same time height as the heart Blood pressure for a healthy 20 year old at rest is 120mm Hg at systole and 70 mm Hg at diastole.Lecture: chapter 42: gas exchange 4/17/12 Fluid return by the lymphatic system The lymphatic system Returns fluid to the body from the capillary beds Aids in body defense Blood clotting When the endothelium of a blood vessel is damaged, the clotting mechanism begins A cascade of complex reactions converts fibrinogen to fibrin, forming a clot A blood clot formed within a blood vessel is called a thrombus and can block blood flow Figure 42.18  Stem cells and the replacement of cellular elements The cellular elements of blood wear out and are replaced constantly throughout a person’s life. Erythrocytes, leukocytes, and platelets all develop from a common source of stem cells in the red marrow of bones. The hormone erythropoietin (EPO) stimulates erythrocyte production when oxygen delivery is low. Cardiovascular disease Are disorders of the heart and the blood vessels Account for more than half of the deaths in the US One type of cardiovascular disease, atherosclerosis, is caused by the buildup of LDL cholesterol within arteries Gills in aquatic animals Gills are outfoldings of the body that create a large surface area for gas exchange Tracheal systems in insects The tracheal system of insects -consists of tiny branching tubes that penetrate the body The tracheal tubes -supply O2 directly to body cells Mammalian respiratory systems: a closer look Figure 42.24 Lecture: chapter 42 gas exchange 4/19/12 How a bird breathes Besides lungs, birds have 8 or 9 air sacs that function as bellows that keep air flowing through the lungs. Control of breathing in humans Sensors in the aorta and carotid arteries monitor O2 and CO2 concentrations in the blood. These sensors exert secondary control over breathing. Figure 42.28 Carbon dioxide transport Hemoglobin also helps transport CO2 and assists in buffering. CO2 from respiring cells diffuses into the blood and is transported either in blood plasma, boundto hemoglobin, or as bicarbonate ions (HCO3-). Elite animals athletes Migratory and diving mammals -have evolutionary adaptations that allow them to perform extraordinary feats. Deep-diving air breathers -stockpile O2 and deplete it slowly -also have myoglobin in their muscles which helps to store more O2. You should know: Compare and contrast open and closed circulatory systems Compare and contrast the circulatory systems of fish, amphibians, non-bird reptiles, and mammals or birds Distinguish between pulmonary and systemic circuits and explain the function of each Trace the path of a red blood cell through the human heart, pulmonary circuit, and systemic circuit Define cardiac cycle and explain the role of the sinoatrial node Relate the structures of capillaries, arteries, and veins to their function Define blood pressure and cardiac output and describe two factors that influence each Explain how osmotic pressure and hydrostatic pressure regulate the exchange of fluid and solutes across the capillary walls Describe the role played by the lymphatic system in relation to the circulatory system  Describe the function of erythrocytes, leukocytes, platelets, fibrin Distinguish between a heart attack and stroke Discuss the advantages and disadvantages of water and of air as respiratory media For humans, describe the exchange of gases in the lungs and in tissues0Chapter 44: Osmoregulation and excretion Osmosis and osmolarity If 2 solutions are isoosmotic, the movement of water is equal in both directions. If 2 solutions differ in osmolarity, the net flow of water is from the hypoosmotic (solute concentration lower than environment) to the hyperosmotic (solute concentration higher than environment) solution. Most animals are stenohaline; they can’t tolerate substantial changes in external osmolarity Euryhaline animals can survive large fluctuations in external osmolarity. Figure 44.4 Land animals Land animals manage water budgets by drinking and eating moist foods and using metabolic water. Desert animals get major water savings from simple anatomical features and behaviors such as anocturnal life style.  Transport epithelia in Osmoregulation Figure Forms of nitrogenous waste Different animals excrete nitrogenous wastes in different forms: Ammonia- fish Urea- mammals Uric acid- birds/reptiles Diverse excretory systems Most excretory systems produce urine by refining a filtrate derived from body fluids Key functions of most excretory systems: Filtration: pressure-filtering of body fluids Reabsorption: reclaiming valuable solutes Secretion: adding toxins and other solutes from the body fluids to the filtrate Excretion: removing the filtrate from the system Structure of the