Chapter 42: Circulation & gas exchange

1. AP Biology: Mrs. Hennings 2009 Chapter 42: Circulation & gas exchange

4. Trading Places…. • All animals need to exchange substances with their environments • This exchange ultimately happens at the cellular level • In multicellular animals there are specialized systems to carry out exchange

5. Remember Diffusion??? • Small nonpolar molecules such as oxygen and carbon dioxide can move between cells and their surroundings by diffusion • Diffusion is a very slow process for more than a few mm distance • Natural selection – 2 adaptations • Body size keeps most cells in contact with environment • Circulatory system

6. Gastrovascular cavities • Some animals don’t have a circulatory system • Hydras and other cnidarians • Planarians and other flatworms

7. Open & Closed Circulation • Animals with lots of cell layers- too thick for diffusion • Circulatory system minimizes distance of exchange • A circulatory system has 3 parts: • Circulatory fluid • Interconnecting tubes • Muscular pump- the heart

8. Open Circulatory System • Arthropods and mollusks • Circulatory fluid baths organs directly • Fluid is called “hemolymph”

9. Closed Circulatory System • Blood confined to vessels and is separate from interstitial fluid • High blood pressures- fast delivery

10. Open vs. Closed Circulation

11. Evolution of vertebrate circulatory system fish amphibian reptiles birds & mammals 2 chamber 3 chamber 3 chamber 4 chamber Birds ANDmammals! Wassssup?! V A A A A A A A V V V V V

12. Cardiovascular System • Closed circulatory system • Arteries, veins, capillaries • Arteries- blood away from heart to organs • Arterioles- in organs smaller branches of arteries- carry it to capillaries. • Capillaries- microscopic with capillary beds • Venules- and Veins- carry blood back to heart

13. Which way to travel??? • Arteries – carry blood AWAY from the heart.Veins – carry blood TO the heart Hearts of all vertebrates have atria (receive) And ventricles that pump out

14. Single circulation • Bony fish, ray, sharks • Two chambers- an atrium and ventricle

15. Double circulation • Amphibians • Reptiles • Mammals • Pumps for 2 circuits serve different tissues but combined into 1 heart

16. Adaptations of Double Circulatory Systems • Amphibians: Heart with 3 chambers: • Two atria and one ventricle • Ridge in ventricle diverts 90% of oxygenated poor blood from RA to the pulmonary circuit- and most of the oxgen rich blood from LA to the systemic circuit • When underwater- a frog shuts off lung circulation- and blood flow continues under the skin.

17. Amphibian Circulation Summary • Three chambered heart • 2 atria and one ventricle • Two circuits of blood • Pulmocutaneous • Systemic

18. Reptiles ( Except for birds) • Lizards, snakes, turtles- • 3 chambered heart • Septum partially divides single ventricle • In crocodilians the septum is complete so they have 4 chambers

19. Mammals and birds • Ventricle is completely divided • 2 atria and 2 ventricles • Left side receives and pumps oxygen rich blood • Right side receives and pumps oxygen poor blood • Powerful 4 chambered heart supports endothermic life

21. Mammalian Circulation • Right ventricle- contracts- blood goes to lungs via the pulmonary arteries • Blood flows through capillaries in lungs and loads up with oxygen and unloads carbon dioxide • Oxygen rich blood goes back to heart via the pulmonary veins • It is dumped into the left atrium

22. Mammalian circulation Contd. • It flows from LA to LV and then is pumped out to the body tissues • Blood goes out of the LV via the aorta • The first branches off the aorta are the coronary arteries ( the best for the heart) • Branches lead to head and arms (ascending) • Branches lead to abdomen (descending) and legs • Oxygen poor blood in head and neck- superior vena cava into RA • Oxygen poor blood in legs etc- inferior vena cava into RA

23. Coronary arteries bypass surgery

25. How does the heart work? • Behind sternum- breastbone • Size of clenched fist • Mostly made of cardiac muscle • Two atria • Two ventricles • Contracts and relaxes in rhythmic cycle • One complete sequence of pumping and filling is the cardiac cycle

26. The contraction phase is called systole • The relaxation phase is called diastole • The volume of blood pumped per min is called the cardiac output- normal 5 L/min • There are two things that determine cardiac output • Heart rate ( per min) • Stroke volume ( amount of blood pumped by a ventricle in one contraction) – 70 mL

27. There are valves- keep blood moving in correct direction • Made of flaps of connective tissue • AV valve- between each atria and ventricle • Semilunar valves- at 2 exits of heart where aorta leaves ventricle and pulmonary artery leaves right ventricle • Heart sounds- Lub= blood against closed AV valves • Dub= recoil of blood against semilunar • Heart murmur- if blood squirts back by defective valve

28. Cardiac Output Amount of blood pumped by each ventricle in one minute CO = Heart rate X Stroke volume Stroke volume—amount of blood ejected from ventricle with each heart beat—70 ml 75 bpm X 70 ml = 5250 ml/min (5.25L)

29. Heart murmurs • Some congenital • Damaged by rheumatic fever • Group A strep bacteria • Endocarditis • Can replace valve if needed

30. Keeping the beat… • Heartbeat starts in heart • Cardiac cells are autorhythimic without signal from nervous system • Heart cells removed from heart beat in a dish! • Group of cells in RA- SA node- pacemaker • Sets rate and timing • SA node generates electrical signal • EKG can measure currents

31. EKG

32. SA node impulse spreads through atria- contract together • AV node- slight delay before reach ventricles • Delay allows atria to empty • AV node then conducts to ventricles where special muscle fibers called bundle branches and Purkinjie fibers conduct

33. Control of the beat… • Physiological cues- regulate SA node • Two sets of nerves: sympathetic and parasympathetic • One set speeds up pacemaker and other slows it down • Stand up- sympathetic nerves increase HR • Sit down- parasympathetic nerves decrease HR • Hormones influence- EPINEPHRINE • Body temperature faster if fever

34. How does it get the right beat?

37. PMI

38. Blood Flow • Basic Blood Vessel Structure & Function • Central lumen ( cavity) lined with endothelium- minimizes resistance to blood flow • Surrounding endothelium specialized tissues that differ depending on job of vessel

39. Blood vessels arteries veins artery arterioles venules arterioles capillaries venules veins

40. capillaries • Smallest blood vessel • Diameter only slightly larger than RBC • Thin walls • Endothelium and basal lamina • Structure facilitates exchange of substances

41. Arteries • More complex than capillaries • Two layers of tissue surrounding endothelium • Outer layer of connective tissue- elastic • Middle layer- smooth muscle • Wall is 3 times as thick vs. vein • Can pump at high pressure • Signals from nervous system and hormones

42. Veins • 2 layers of tissue-like arteries • Thinner walls compared to arteries • Valves maintain one way blood flow

43. Velocity of Blood • What influences flow rate? • Diameter of hose! • Blood slows from arteries to capillaries- because there are many more capillaries compared to large vessels. • Blood moves 500 times slower in capillaries compared to aorta!

44. Blood Pressure • Moves from high pressure to low pressure • Contractions of heart make pressure • Arterial pressure highest when heart contracts called systolic pressure • Pulse- heart rate- • When ventricles relax- diastolic pressure

45. Regulation of BP • Two time scales- • Cardiac cycle oscillations • Longer time scale • Vasoconstriction- smooth muscles in arteriole walls contract- increases BP • Vasodilatation- increase in diameter BP decreases

47. Measurement of blood pressure • High Blood Pressure (hypertension) • if top number (systolic pumping) > 150 • if bottom number (diastolic filling) > 80

48. Fluid Return by Lymph System • 85% of fluid that leaves capillaries is returned to capillaries • Imbalance loss of 4L of fluid from capillaries to tissues • Lost fluid and proteins return to blood system via the lymphatic system • Lymph- drains into circulatory system • Lymph Nodes- organs- filtering lymph and house to cells that are fighters

49. Lymphatic system • Parallel circulatory system • transports white blood cells • defending against infection • collects interstitial fluid & returns to blood • maintains volume & protein concentration of blood • drains into circulatory system near junction of vena cava & right atrium

50. Lymph System