Circulation and Gas Exchange

1. Circulation and Gas Exchange AP Biology

2. Invertebrate Open Circulatory System • Arthropods and mollusks • Blood and interstitial fluid are the same (hemolymph) • Tubular heart pumps hemolymph through a dorsal vessel out into sinuses • Hemolymph bathes cells and allows for exchange of nutrients • When heart relaxes, hemolymph flows back into vessels through ostia • Body movements squeeze sinuses to aid circulation

3. Invertebrate Closed Circulatory System • Annelids (earthworms) have closed circulatory system • 5 Aortic arches or ‘hearts’ force blood down to the ventral vessel, which carries blood to posterior and up to complete the circuit • Blood carries O2 and CO2 between cells and the skin where gas exchange takes place • Blood also circulates nutrients from digestive tract to the rest of the body

4. Vertebrate Circulatory System • Closed system with a chambered heart that pumps blood through arteries that lead away from the heart to capillaries. • Capillaries—small vessels in tissues where exchange of materials take place • Blood is carried back to heart through veins

5. Fish • 2 chamber heart • One artrium • One ventricle • Blood from ventricle picks up O2 in gills, then is collected into a large artery to pass directly to the rest of the body before returning to the atrium

6. Amphibian • 3 chamber heart • Two artria • One ventricle • Ventricle pumps blood to both the lungs and the rest of the body simultaneously through 2 different major arteries • Allows oxygenated blood from lungs and deoxygenated blood from the body to mix in the ventricle before it is delivered back to the body • Allows higher arterial pressure in blood pumped to vessels

7. Birds and Mammals • 4 chamber heart • Two artria • Two ventricle • Higher metabolic need met by division of heart into 2 pumps • Right atrium and ventricle pumps deoxygenated blood to lungs through pulmonary circulation • Left atrium and ventricle pumps oxygenated blood to the rest of the body through systemic circulation • Avoids mixing of oxygenated and deoxygenated blood • Allows high arterial pressure required for quick delivery

8. Human Heart • Located beneath the sternum • About the size of your fist • Composed mostly of cardiac muscle tissue • 2 atria have thin walls and function as collection chambers for returning blood • 2 ventricles have thick, powerful walls that pump blood to the organs

9. Four valves function to prevent backflow of blood • Atrioventricular valves • Prevent backflow when ventricles contract • Semilunar valves • Prevent backflow when ventricles relax

10. Cardiac Cycle • Systole—heart muscles contract and the chambers pump blood • Diastole—heart muscles relax and fills with blood • Cardiac output—volume of blood per minute that the left ventricle pumps into the systemic circuit

12. Control of Heart Rhythm • Sinoatrial (SA) node—cells are self-excitable—generate electrical impulses • Cardiac muscle cells are electrically coupled by intercalated discs b/w cells

13. Control of Heart Rhythm • Atrioventricular (AV) node—receives signal from atria, delays 0.1 sec, and then sends signal throughout walls of ventricle via the bundle branches and Purkinje fibers

14. Blood Vessels • Arteries—carry blood away from the heart to the tissues • Branch into smaller arterioles, which supply blood to tissues via capillaries • Thick-walled, muscular (smooth muscle), and elastic, transporting blood at high pressure • Blood is oxygenated, except the pulmonary artery that carries deoxygenated blood from tissues to lungs through the right atrium and ventricle

15. Veins—carry blood to the heart from the capillaries • Capillaries branch into larger venules, which supply blood to veins and back to the heart • Thin-walled, little smooth muscle, transporting blood at low pressure, and contain many valves to prevent backflow • Veins have no pulse and carry deoxygenated blood, except the pulmonary vein which carries oxygenated blood from the lungs • Skeletal muscle contraction aids in systemic circulation

17. Capillaries—thin-walled vessels (simple squamous) • Permit exchange of materials between blood and body cells • Controlled by precapillary sphincters

18. Capillaries • Fluid containing water with nutrients and hormones seep from capillaries into tissues, driven by pressure • Cells and proteins are retained in the capillaries and draw water back into the capillaries by osmosis • Excess fluid in tissue can enter lymphatic system to be filtered and cycled back to the circulatory system

20. Capillary Exchange

21. Regulation of Blood Flow • Regulated to match the metabolic needs • Smooth muscle in walls of arterioles constrict to reduce blood flow to capillaries • Smooth muscle relaxes when blood leaving capillaries is low in O2, allowing more blood to flow through capillary bed

22. Regulation of Blood Flow • Secretion of epinephrine by adrenal glands  heart rate and constricts arteries to  arterial pressure • Angiotensin secreted from the kidney acts on smooth muscle in the arterioles and arteries to cause constriction and  arterial pressure • Vasopressin secreted by posterior pituitary in response to stretch sensors causes constriction in arterioles and arteries to  arterial pressure

24. Erythrocytes: Red Blood Cells • Primary function to carry oxygen • Production in red bone marrow of bones stimulated by erythropoietin (produced by kidneys) • Mature cells lack nuclei and circulate ~4mos. • Mature cells lack mitochondria—produce ATP without oxygen through glycolysis • Contain hemoglobin-pigment that binds oxygen

25. Erythrocytes: Red Blood Cells • Red blood cells (rbc) manufacture 2 antigens, antigen A (Blood Type A) and antigen B (Blood Type B) • Plasma carries antibodies for the antigens that are not present on the rbcs

26. Leukocytes: White Blood Cells • Involved in immune functions in the body • Phagocytes—engulf bacteria • Neutrophils—1st to arrive at site of inflammation • Macrophages and Monocytes • Lymphocytes (B and T cells)—immune response • B cells produce antibodies • Helper T cells kill infected cells

28. Leukocytes: White Blood Cells • Platelets—cell fragments produced in marrow • Involved in blood clotting mechanism • Activation of protease thrombin cleaves fibrinogen protein in the blood to make fibrin that polymerizes to for a net across the wound, trapping more cells and blocking the flow of blood

29. Cardiovascular Disease • Heart attack—death of cardiac muscle tissue resulting from artery blockage of one or more coronary arteries which supply oxygen to the heart • Stroke—death of nervous tissue in the brain resulting from artery blockage in the head

31. Cardiovascular Disease • Atherosclerosis—plaques develop on inner walls of arteries • Forms where smooth muscle thickens abnormally and is infiltrated by fibrous connective tissue • Arteriosclerosis—hardening of the arteries by calcium deposits • Hypertension—high blood pressure

33. Cardiovascular Disease • Hypertension and atherosclerosis have genetic component and environmental component (smoking, lack of exercise, high fat and cholesterol diet) • Low-density lipoproteins (LDLs)—add deposits of cholesterol in arterial plaques • High-density lipoproteins (HDLs)—may reduce cholesterol deposition • Exercise increases HDL concentration • Smoking increases LDL concentration

34. Gas Exchange • Involves both Respiratory system and Circulatory system

35. Invertebrate Gas Exchange • Water contains less oxygen than air • As an adaptation, most aquatic animals have gills • Total surface area of gills is often larger than that of the rest of the body

36. Invertebrate Gas Exchange • Arthropods respiratory system consists of a series of respiratory tubules, tracheae • Open to the outside in the form of pairs of orifices called spiracles • Tracheae subdivide into smaller and smaller branches, to make close contact with most cells • Direct diffusion through tracheae is one factor that limits body size in arthropods

37. Fish

38. Countercurrent Exchange • Maximizes exchange of gases between blood inside the gills and the water flowing over the gills • Blood flows through capillaries in direction opposite of water flowing across gills

39. Amphibians • Simple air sac with little surface area • Must supplement gas exchange in lungs with exchange across the thin moist skin

41. Ventilating Lungs: Breathing

42. Automatic Control of Breathing • Breathing control center in brain = medulla oblongata and pons • Monitors CO2 levels in blood by changes in pH • CO2 + H2O  Carbonic acid •  pH =  depth and rate of breathing • altitude =  O2 levels • Sensors in aorta and carotid arteries detect and signal control center to  breathing rate

43. Loading and Unloading of Respiratory Gases

48. Oxygen Transport • Oxygen carried by respiratory pigments • Invertebrates utilize hemocyanin—Cu is the oxygen-binding component • Vertebrates utilize hemoglobin—four heme groups surrounding an Fe atom • Can carry four oxygen atoms

49. Oxygen Dissociation Curves for Hemoglobin

50. Carbon Dioxide Transport • Hemoglobin transports CO2 and assists with buffering the blood—prevents dramatic changes in pH • 7% CO2 released by cells transported as dissolved CO2 • 23% binds to amino group of hemoglobin • 70% transported in form of bicarbonate ions in red blood cells