Chapter 21

1. Chapter 21 Blood Vessels and Circulation

2. Blood Pressure and Cardiovascular regulation Exercise

3. arteries arterioles capillaries venules veins carry blood away from heart thicker walls (smooth muscle) branch and get narrower bifurcation (tri-, rami-) smallest vessels in networks (beds) exchange with ECF carry blood back to heart thinner walls small v. join to form larger veins anastomosis

4. blood circuit fig. 21-8

5. 100 keys (pg. 725) “It is blood flow that’s the goal, and total peripheral blood flow is equal to cardiac output. Blood pressure is needed to overcome friction and elastic forces and sustain blood flow. If blood pressure is too low, vessels collapse, blood flow stops, and tissue die; if blood pressure is too high, vessel walls stiffen and capillary beds may rupture.”

6. 100 keys (pg. 732) “Cardiac output cannot increase indefinitely, and blood flow to active versus inactive tissues must be differentially controlled. This is accomplished by a combination of autoregulation, neural regulation and hormone release.”

7. Controlling CO and bp Autoregulation of blood flow Neural mechanisms Hormonal mechanisms * *

8. CO = HR x SV neural mechanisms (reflex control of cardiovascular function)

9. Neural mechanisms Reflex control of cardiovascular function baroreceptors blood pressure chemoreceptors pH, [gases] negative feedback loops

10. Neural mechanisms Reflex control of cardiovascular function baroreceptors monitor degree of stretch in walls of expandable organs carotid sinuses aortic sinuses atrium

11. baroreceptors if blood pressure climbs • decrease cardiac output • lower HR (ACh SA) • vasodilation • lowers peripheral resistance reflex: reduce blood pressure

12. baroreceptors if blood pressure falls • increase cardiac output • NE on heart • vasoconstriction • NE inc. peri. resistance reflex: increase blood pressure

13. baroreceptors atrial reflex stretching the atrium (more blood returning) will stimulate cardiac output (more blood leaving)

14. baroreceptors Valsalva maneuver exhale forcefully close glottis

15. baroreceptors Valsalva maneuver brief rise in bp pressure on lungs sends pulmonary blood to atria bp falls reduced venous return low CO reflexive vasoconstriction increase in heart rate

16. baroreceptors Valsalva maneuver • release pressure expansion of vessels (bp6) (6return, 5aortic volume) 4. restore normal blood return up CO is up BP is up

17. graph of bp drop and HR increase during Valsalva

18. to here 4/2/07 Lec # 34

19. fig. 21-14

20. Neural mechanisms Reflex control of cardiovascular function baroreceptors chemoreceptors

21. Neural mechanisms chemoreceptors monitor pH (H+) [CO2] [O2] of blood and CSF sensory neurons in: carotid body aortic bodies (med. oblong.)

22. Neural mechanisms chemoreceptors pH drops (H+5) or 5[CO2] or 6[O2] reflex stimulation of cardio- acceleratory centers (sym) stimulate vasomotor (vasoconstriction)

23. Neural mechanisms chemoreceptors pH drops (H+5) or 5[CO2] or 6[O2] increase cardiac output peripheral vasoconstriction increase bp

24. Neural mechanisms chemoreceptors pH drops (H+5) or 5[CO2] or 6[O2] receptors in medulla obl. stimulate respiratory centers more O2 and more venous return

25. Neural mechanisms chemoreceptors pH drops (H+5) or 5[CO2] or 6[O2] increased bp and resp. more O2 to cells

26. fig. 21-15 here

27. CO = HR x SV hormonal control neural mechanisms NE, E ADH angiotensin II EPO natriuretic peptides all regulate blood volume

28. ADH Antidiuretic hormone made in hypothalamus released from posterior pituitary gland in response to 6 blood volume vasoconstriction (5bp) H2O recovery in kidney

29. angiotensin II fall in bp renin release from kidney angiotensinogen (from liver) angiotensin I angiotensin II renin ACE

30. angiotensin II four functions: stimulates kidney to produce aldosterone stimulates secretion of ADH stimulates thirst stimulates CO and vasconstriction (bp)

31. EPO erythropoietin released from kidneys low bp low O2 levels stimulates bone marrow to make more RBC’s

32. natriuretic peptides natrium = sodium (Na) atrial natriuretic peptide (ANP) brain natriuretic peptide (BNP) released in response to stretching reduce blood volume reduce blood pressure

33. natriuretic peptides increase Na+ excretion at kidney increase volume of urine produced reduce thirst block ADH, NE, E, aldosterone release stimulate peripheral vasodilation reduce blood volume and blood pressure

34. response to decrease in bp fig 21-16a

35. response - increase in bp fig 21-16b

36. 100 keys (pg. 732) “Cardiac output cannot increase indefinitely, and blood flow to active versus inactive tissues must be differentially controlled. This is accomplished by a combination of autoregulation, neural regulation and hormone release.”

37. fig. 20-23

38. Summary hormones venous return filling time venous return preload contractility afterload Heart rate EDV ESV SV = EDV-ESV CO = HR x SV

39. Exercise light slight sympathetic innervation slight increase in HR vasodilation get blood to tissues resistance drops more blood flows

40. Exercise light increase in venous return muscle pumps

41. muscle activity venous return fig. 21-6

42. Exercise light increase in venous return muscle pumps increase respiratory pump cardiac output increases due to higher venous return

43. Exercise heavy more sympathetic stimulation vasocontriction to “non-essentials” (most internal organs except brain) blood lungs skeletal muscle - heart - - heart -