1. Cardiovascular Physiology
Qiang XIA (夏强), MD & PhD
Department of Physiology
Room C518, Block C, Research Building, School of Medicine
Tel:

2. Regulation of Cardiovascular Activities
Lecture Outline
Nervous Regulation
Humoral Regulation
Autoregulation

3. Nervous Regulation

4. Innervation of cardiovascular system

5. Nervous regulation of the circulation

6. Cardiac mechanisms of norepinephrine

7. Mechanisms of norepinephrine —increase Na+ & Ca2+ permeability
If , phase 4 spontaneous depolarization, autorhythmicity 
Ca2+ influx , phase 0 amplitude & velocity , conductivity 
Ca2+ influx , Ca2+ release , [Ca2+ ]i , contractility 

8. Asymmetrical innervation of sympathetic nerve

9. Cardiac mechanisms of acetylcholine

10. Mechanisms of acetylcholine —increase K+ & decrease Ca2+ permeability
K+ outward , |MRP| , phase 4 spontaneous depolarization , autorhythmicity 
Inhibition of Ca2+ channel, phase 0 amplitude & velocity , conductivity 
Ca2+ influx , [Ca2+ ]i , contractility 

11. Cardiac effect of parasympathetic stimulation

12. Interaction of sympathetic and parasympathetic nerves

13. Predominance of autonomic nerves

14. Cardiovascular Center
A collection of functionally similar neurons that help to regulate HR, SV, and blood vessel tone

15. Vasomotor center
Located bilaterally mainly in the reticular substance of the medulla and of the lower third of the pons
Vasoconstrictor area
Vasodilator area
Cardioinhibitor area – dorsal nuclei of the vagus nerves and ambiguous nucleus
Sensory area – tractus solitarius

16. Vasomotor center

17. Higher cardiovascular centers
Reticular substance of the pons
Mesencephalon
Diencephalon
Hypothalamus
Cerebral cortex
Cerebellum

18. Baroreceptor Reflexes
Arterial baroreceptors
Carotid sinus receptor
Aortic arch receptor
Afferent nerves (Buffer nerves)
Cardiovascular center: medulla
Efferent nerves: cardiac sympathetic nerve, sympathetic constrictor nerve, vagus nerve
Effector: heart & blood vessels

19. Baroreceptor neurons function as sensors in the homeostatic maintenance of MAP by constantly monitoring pressure in the aortic arch and carotid sinuses.

21. Characteristics of baroreceptors:
Sensitive to stretching of the vessel walls
Proportional firing rate to increased stretching
Responding to pressures ranging from mmHg
Receptors within the aortic arch are less sensitive than the carotid sinus receptors

23. The action potential frequency in baroreceptor neurons is represented here as being directly proportional to MAP.

24. i.e., reduce cardiac output
i.e., MAP is
above
homeostatic
set point
i.e., reduce cardiac output
Baroreceptor neurons deliver MAP information to the
medulla oblongata’s cardiovascular control center (CVCC);
the CVCC determines autonomic output to the heart.

25. Reflex pathway

26. Typical carotid sinus reflex

27. Physiological Significance
Maintaining relatively constant arterial pressure, reducing the variation in arterial pressure

28. Humoral Regulation
Vasoconstrictor agents
Vasodilator agents

29. Renin-angiotensin system

30. Juxtaglomerular cell
Renin

31. Physiological effects of angiotensin II
Constricts resistance vessels
Acts upon the adrenal cortex to release aldosterone
Stimulates the release of vasopressin
Facilitates norepinephrine release from sympathetic nerve endings
Stimulates thirst centers within the brain

32. Epinephrine & Norepinephrine
Sources
Epinephrine----
adrenal medulla
Norepinephrine----
sympathetic nerves

33. Catecholamines
Norepinephrine
Epinephrine

34. Effects Epinephrine Norepinephrine
Receptor a-adrenoceptor
b-adrenoceptor
Heart heart rate (in vitro) － (in vivo)
cardiac output ±
Vessels constriction (skin, visceral)
relaxation (SM, liver) －
total peripheral resistance ±
Blood pressure systolic
diastolic ±
MAP
Clinical application positive inotropic pressor agent
agent

36. A 23-year-old woman presents to your emergency service with an anaphylactic reaction after being stung by several bees. She complains of wheezing and shortness of breath. On examination, the client is in acute distress. BP is 98/56 mmHg, PR 110/min, RR 28/min, and temperature 98.7°F. She is immediately treated with supplemental oxygen. In treating this condition further, what drug is required most urgently? A Theophylline B Glucagon C Cimetidine D Methylprednisolone E Epinephrine

37. Vasopressin (antidiuretic hormone, ADH)

39. Endothelium-derived vasoactive substances
Vasodilator factors
PGI2--prostacyclin
EDRF, NO--endothelium-derived relaxing factor, nitric oxide
EDHF--endothelium-dependent hyperpolarizing factor
Vasoconstrictor factors
Endothelin

40. Atrial natriuretic peptide (ANP)
Produces natriuresis and diuresis
Decreases renin release
Reduces total peripheral resistance via vasodilatation
Decreases heart rate, cardiac output

41. Autoregulation Definition:
Intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure, independent of any neural or humoral influences

44. The End.