Cardiovascular System: Circulation Pathways and BP Regulation

1. Cardiovascular System: Circulation Pathways and BP Regulation General Physiology Tony Serino, Ph.D. Biology Department Misericordia University

2. Blood Vessels Types • Arteries –conduct blood away from heart • Elastic arteries, Muscular arteries, arterioles • Veins –conduct blood toward heart • Venules, small and large veins • Capillaries –thinnest blood vessel; used in exchange, is the functional unit of circulatory system (Microcirculation) • AV shunts, metarterioles, pre-capillary sphincters, and capillary bed

3. Capillary

4. Capillary Types Tight Capillary Fenestrated Capillary Sinusoidal Capillary

5. Capillary Bed

6. Forces Affecting Bulk Flow across the Capillary Wall

7. Arteries are known as resistance vessels, especially the arterioles • Arteries withstand the greatest BP • Veins are capacitance vessels, they are able to change the diameter to hold more or less blood Artery vs. Vein

8. Pressure Changes down CV tree Small changes in arteriolar diameter produce big changes in resistance; termed total peripheral resistance (TPR)

9. Elastic Recoil and Artery Contraction

10. Arterial Pressure Curve (Dicrotic Notch)

11. TPR (total peripheral resistance) • TPR is the opposition to blood flow through the vessel (caused by friction) • Arteries with their smaller lumen resist blood flow • Arteriolar diameter contribute the most to TPR • Arteriolar compliance (the ability of the vessel to distend) controls the TPR • Sympathetic innervation controls arteriolar radius • The viscosity of the blood also affects resistance

12. Small changes in Arteriole Diameter create large changes in BP

13. Blood Flow Velocity in Vascular Tree

14. Blood Flow Regulation is mainly a Local Response Understand Reactive Hyperemia and Inflammation; ANS controlmodifies BF based on “whole body needs”

15. ANS Control of Arterioles (Alpha receptors outnumber Beta in most vascular beds; except in skeletal muscles. Here epinephrine causes vasodilation)

16. Modifiers of Arteriolar Radius

17. Adjustment of Perfusion to Exercise

18. CV Adjustment to Exercise

19. Some Exercise Physiology Mechanisms

20. Atherosclerotic plaques are a primary cause of hypertension due to Increase in TPR

21. Skeletal Muscle Pump Capacitance Vessels (Veins)

22. Fig. 12.46

23. Blood Pressure • BP = SP/DP • Systolic Pressure (SP) –the pressure in the artery during systole • Diastolic Pressure (DP) –the pressure in the artery during diastole • Mean Arterial Pressure (MAP) (weighted average)MAP = DP + 1/3 (PP) • Pulse Pressure (PP) = SP - DP • MAP = CO x TPR

25. SP DP

26. Baroreceptor Locations

27. Carotid sinus baroreceptors Cardioregulatory and vasomotor centers in the medulla oblongata Sympathetic nerves 1. Baroreceptors in the carotid sinus and aortic arch monitor blood pressure. 2. Action potentials are conducted by the glossopharyngeal and vagus nerves to the cardioregulatory and vasomotor centers in the medulla oblongata. 3. Increased parasympathetic stimulation of the heart decreases the heart rate. 4. Increased sympathetic stimulation of the heart increases the heart rate and stroke volume. 5. Increased sympathetic stimulation of blood vessels increases vasoconstriction. 1 Aortic arch baroreceptors Glossopharyngeal nerve 3 Vagus nerve 2 Vagus nerve (parasympathetic) 4 Sympathetic chain Blood vessels 5

28. Better at controlling BP dropsthan rise. High BP causesshift in set point of receptorssimilar to exercise.

29. Baroreceptor Reflex(Note: if decrease BP: arrows reverse)

30. Renal Hormonal Control of BP (ACE) ↑ BP ↑ blood volume

31. Other Renal Mechanismsaffecting BP (ADH) ↑ blood volume ↑ BP ↓blood volume ↓ BP

32. Mechanism of BV changes on BP

33. Overview of BP Regulation

35. Compensation Response Hemorrhage Primary Effects

36. Fig. 12.58

37. Fig. 12.06

38. Fig. 12.47

39. Elephantiasis Vector : mosquitoPathogen: filaria worms blocking lymph vessels