1. Nervous Regulation of the Heart
Qiang XIA (夏强), PhD
Department of Physiology
School of Medicine
Tel: ,

2. Innervation of the heart
Cardiac sympathetic nerve
Cardiac vagus nerve
起源origin
节前纤维preganglionic fiber
外周神经节ganglion
节后纤维postganglionic fiber
支配distribution
递质neurotransmitter

7. Cardiac sympathetic actions
Positive chronotropic effect正性变时作用
Positive dromotropic effect正性变传导作用
Positive inotropic effect正性变力作用

8. Cardiac mechanisms of norepinephrine

9. Mechanisms of norepinephrine —increase Na+ & Ca2+ permeability
If  & ICa,T , phase 4 spontaneous depolarization, autorhythmicity 
Ca2+ influx (ICa,L) , phase 0 amplitude & velocity , conductivity 
Ca2+ influx (ICa,L) , Ca2+ release , [Ca2+ ]i , contractility 
(CICR)

11. Asymmetrical innervation of sympathetic nerve

12. Cardiac parasympathetic actions
Negative chronotropic effect负性变时作用
Negative dromotropic effect负性变传导作用
Negative inotropic effect负性变力作用

13. Cardiac mechanisms of acetylcholine

14. Mechanisms of acetylcholine —increase K+ & decrease Ca2+ permeability
K+ outward (GIRK) , If  & ICa,T , |MRP| , phase 4 spontaneous depolarization , autorhythmicity 
Inhibition of Ca2+ channel, phase 0 amplitude & velocity , conductivity 
G protein→PLC → NOS → NO → GC → cGMP  ， Ca2+ influx (ICa,L) , [Ca2+ ]i , contractility 

15. Cardiac effect of parasympathetic stimulation

16. Vagal Maneuvers Valsalva maneuver
A maneuver in which a person tries to exhale forcibly with a closed glottis (the windpipe) so that no air exits through the mouth or nose as, for example, in strenuous coughing, straining during a bowel movement, or lifting a heavy weight. The Valsalva maneuver impedes the return of venous blood to the heart.
Named for Antonio Maria Valsalva, a renowned Italian anatomist, pathologist, physician, and surgeon ( ) who first described the maneuver.

18. Physiological response in Valsalva maneuver
The normal physiological response consists of 4 phases

19. Physiological response in Valsalva maneuver
The normal physiological response consists of 4 phases
Initial pressure rise: On application of expiratory force, pressure rises inside the chest forcing blood out of the pulmonary circulation into the left atrium. This causes a mild rise in stroke volume.
Reduced venous return and compensation: Return of systemic blood to the heart is impeded by the pressure inside the chest. The output of the heart is reduced and stroke volume falls. This occurs from 5 to about 14 seconds in the illustration. The fall in stroke volume reflexively causes blood vessels to constrict with some rise in pressure (15 to 20 seconds). This compensation can be quite marked with pressure returning to near or even above normal, but the cardiac output and blood flow to the body remains low. During this time the pulse rate increases.
Pressure release: The pressure on the chest is released, allowing the pulmonary vessels and the aorta to re-expand causing a further initial slight fall in stroke volume (20 to 23 seconds) due to decreased left ventricular return and increased aortic volume, respectively. Venous blood can once more enter the chest and the heart, cardiac output begins to increase.
Return of cardiac output: Blood return to the heart is enhanced by the effect of entry of blood which had been dammed back, causing a rapid increase in cardiac output (24 seconds on). The stroke volume usually rises above normal before returning to a normal level. With return of blood pressure, the pulse rate returns towards normal.

20. Interaction of sympathetic and parasympathetic nerves

21. Predominance of autonomic nerves

22. Tonus紧张
Cardiac vagal tone心迷走紧张
Cardiac sympathetic tone心交感紧张

23. Innervation of the blood vessels
Vasoconstrictor nerve缩血管神经
Sympathetic vasoconstrictor nerve交感缩血管神经
Vasodilator nerve舒血管神经
Sympathetic vasodilator nerve交感舒血管神经
Parasympathetic vasodilator nerve副交感舒血管神经
Dorsal root vasodilator nerve脊髓背根舒血管神经

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

27. 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

28. Vasomotor center

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

33. Baroreceptor Reflexes 压力感受性反射
Arterial baroreceptors 动脉压力感受器
Carotid sinus receptor
Aortic arch receptor
Afferent nerves (Buffer nerves，缓冲神经)
Cardiovascular center: medulla
Efferent nerves: cardiac sympathetic nerve, sympathetic constrictor nerve, vagus nerve
Effector: heart & blood vessels

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

37. 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

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

39. 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.

40. Reflex pathway

41. Baroreceptor Reflex Control
Click here to play the
Baroreceptor Reflex Control
of Blood Pressure
Flash Animation

42. Typical carotid sinus reflex

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

44. Cardiovascular Responses to Exercise
When exercise begins, mechanosensory input from working limbs combines with descending pathways from the motor cortex to activate the cardiovascular control center in the medulla oblongata.
The center responds with sympathetic discharge that increases cardiac output and causes vasoconstriction in many peripheral arterioles.

45. Cardiac output increases during exercise

47. Peripheral blood flow redistributes to muscle during exercise

48. Blood pressure rises slightly during exercise
VO2 max (also maximal oxygen consumption, maximal oxygen uptake or aerobic capacity) is the maximum capacity of an individual's body to transport and utilize oxygen during incremental exercise, which reflects the physical fitness of the individual.

49. Baroreceptor reflex adjusts to exercise
During exercise, blood pressure increases without activating homeostatic compensation of baroreceptor reflex
Why?
Signal from the motor cortex during exercise reset the arterial baroreceptor threshold to a higher pressure

51. The End.