Circulation and Gas Exchange Chapter 42

1. Circulation and Gas Exchange Chapter 42

3. Overview: Trading with the Environment • Every organism must exchange materials & energy with environment • Exchanges ultimately occur at the cellular level

4. In unicellular organisms, exchanges occur directly with environment

5. In multicellular organisms, direct exchange with environment not possible with all internal cells Diffusion always at cellular level BUT diffusion over long dist (lung to internal cells) too slow Therefore developed physiological systems specialized for transport (circulatory) & exchange (respiration)

6. Concept 42.1: Circulatory systems reflect phylogeny • Diffusion alone not adequate for transporting substances over long distances within animals • Therefore complex animals have internal transport systems (circulatory systems) that circulate fluid & connect the organs of exchange with the body cells for exchg

7. Invertebrate Circulation • The wide range of invertebrate body size & form plus differences in environmental pressures = diversity in circulatory systems Gastrovascular cavities

8. Open and Closed Circulatory Systems Complex animals with many cell layers have: - open circulatory system - closed circulatory system Both have 3 components in common: 1. circulatory fluid (blood or hemolymph 2. set of tubes (blood vessels) 3. muscular pump (heart provides pressure to move fluid)

9. In insects, other arthropods, & molluscs blood bathes organs directly in open circ system no distinction between blood & interstitial fluid; general body fluid = hemolymph

10. Closed circulatory system = blood confined to vessels & distinct from interstitial fluid Closed systems more efficient at transporting circ fluids to tissues & cells (worm is an example)

11. Vertebrate Circulation Humans & other vertebrates blood flows in closed circulatory system (blood vessels & 2- 4-chambered heart) = cardiovascular system - arteries: carry blood to capillaries, sites of chemical & gas exchange between blood & interstitial fluid (single cell layer that gas exchanges) - veins: return blood from capillaries to heart

12. Fishes • 2 main chambers: ventricle & atrium • Blood pumped from the ventricle travels to the gills, where it picks up O2 and disposes of CO2

13. Amphibians • Frogs and other amphibians have a three-chambered heart: 2 atria & 1 ventricle R atrium L atrium Ventricle

14. Reptiles Reptiles have double circulation, with a pulmonary circuit (lungs) and a systemic circuit One can say that the reptile heart has 3 chambers, 2 atria & 1, partially divided, ventricle. Or one may argue that reptiles have 4-chambered hearts with 2 atria & 2 ventricles, but the wall between the ventricles is incomplete.

15. Mammals and Birds In all mammals & birds, ventricle divided into separate R & L chambers L side : pumps & receives only O2-rich blood R side: receives & pumps only O2-poor blood

17. A powerful four-chambered heart was an essential adaptation of the endothermic way of life characteristic of mammals and birds Endotherms need 10x energy as equal-sized ectotherm so must deliver more via blood

18. Concept 42.2: Double circulation in mammals depends on anatomy & pumping cycle of heart The human circulatory system serves as a model for exploring mammalian circulation

19. Mammalian Circulation: The Pathway • Heart valves dictate a one-way flow of blood through the heart • Blood begins its flow with R ventricle pumping blood to lungs • In lungs, blood loads O2 & unloads CO2 • O2-rich blood from lungs enters heart at L atrium & into L ventricle where then pumped to body tissues • Blood returns to heart at R atrium

21. The Mammalian Heart: A Closer Look provides a better understanding of dbl circ Valves

22. Cardiac cycle -contraction, or pumping, phase = systole - relaxation, or filling, phase = diastole

23. Heart sounds, heard with stethoscope, caused by closing of valves. “lub-dup, lub-dup” Lub=close AV Dub=close semilunar

24. Heart murmur = defect in valve detectable as a hissing sound when blood squirts backward through it Rheumatic fever can cause

25. Heart rate = pulse = beats per minute Cardiac OP = volume blood pumped into systemic circ per minute Stroke vol = amt blood pumped by L ventricle per contraction ________________________________________ Av stroke vol … 75 ml Av ht rate ……..70/min Cardiac OP: 75 * 70 = (5,250 ml) 5.25 L/min

26. Heart’s Rhythmic Beat Cardiac muscle stims self = contract without signal from nervous syst Pacemaker influenced by nerves, hormones, body T, & exercise Impulses during cardiac cycle can be recorded as an electrocardiogram (ECG or EKG)

27. Concept 42.3: Physical principles govern blood circulation Structure/function: arteries, veins, & capillaries Velocity blood flow slowest in capillary beds

28. - arteries: thick wall + muscle - veins: blood flow result muscle action; valves

29. - Exchange materials & gases at capillaries - BP at capillaries pushes fluid out into tissues 5,000 4,000 3,000 Area (cm2) 2,000 1,000 0 50 40 Velocity (cm/sec) 30 20 10 0 120 Systolic pressure 100 80 Pressure (mm Hg) 60 Diastolic pressure 40 20 0 Venae cavae Aorta Capillaries Venules Veins Arterioles Arteries

30. Fluid in tissues & 85% reenters at venous end Remaining 15% returned via lymphatic system

31. Critical exchange between blood & interstitial fluid takes place across thin endothelial walls capillaries Diff between BP & π drives fluids out capillaries at arteriole end & into capillaries at venule end

32. Fluid Return by the Lymphatic System • The lymphatic system returns fluid to the body from the capillary beds • This system role in body defense • Fluid reenters the circulation directly at the venous end of the capillary bed & indirectly through the lymphatic system

33. Concept 42.4: Blood is a connective tissue with cells suspended in plasma 5 types Leukocytes

34. Cellular Elements Suspended in blood plasma - red blood cells (erythrocytes) transport O2 - white blood cells (leukocytes) body defenses - platelets = frags cells & involved in clotting

35. Stem Cells & Replacement of Cellular Elements erythropoietin pluripotent stem cells in red marrow of bones

36. Blood Clotting hemophilia thrombus Cascade rxs (fibrinogen to fibrin) = clot

37. Cardiovascular Disease disorders of heart & blood vessels account for > half deaths in United States Artheroscloresis: accumulation cholesterol in arteries

38. Chlosterol transported as lipid:prot particles LDL (low density lipoprot) = “BAD” cholesterol HDL (high density lipoprot) = “GOOD” cholesterol Satd fats = ↑ tendency artherosclerotic plaques

39. Hypertension, or high blood pressure, promotes atherosclerosis and increases the risk of heart attack and stroke • Aheart attack is the death of cardiac muscle tissue resulting from blockage of one or more coronary arteries • Astrokeis the death of nervous tissue in the brain, usually resulting from rupture or blockage of arteries in the head (can be side effect of heart attack)

40. Concept 42.5: Gas exchange occurs across specialized respiratory surfaces Gas exchange = uptake O2 from environment & discharge CO2(from cell resp) to environment Animals require large, moist respiratory surfaces for adequate diffusion of gases between their cells & the respiratory medium…. air for terrestrial animals and water for most aquatic animals

41. O2 CO2 Respiratory medium (air or water) Respiratory surface Organismal level Circulatory system Cellular level Energy-rich fuel molecules from food ATP Cellular respiration Structure of respiratory surface depends on size of organism & whether it lives in water or on land

42. - Have gills = outfoldings of body surface suspended in water - Water [O2] low so special processes to ↑ efficiency of exchg A. Water Habitat

43. B. Terrestrial Habitat Tracheal system of insects consists of tiny branching tubes that penetrate the body The tracheal tubes supply O2 directly to body cells

44. Lungs Most terrestrial vertebrates have internal lungs

45. system of branching ducts conveys air to lungs Air inhaled through the nostrils passes through pharynx into trachea, bronchi, bronchioles, & dead-end alveoli, where gas exchange occurs

46. Mammals ventilate their lungs by neg pressure Inhale = ↑vol lung = pulls air into the lungs Exhale = musc relax & elastic fibers retract lung

47. Main breathing control center in brain which regulates rate & depth of breathing in response to pH changes in Cerebrospinal fluid Sensors in aorta & carotid arteries monitor O2 & CO2 concentration in blood = exert 2ndary control over breathing

48. Gases diffuses from higher partial pressure (conc) to lower partial pressure

49. Oxygen Transport Hemoglobin reversibly binds O2 - loads O2 in lungs - unloads it in other parts body

50. Drop in pH lowers affinity of hemoglobin for O