基础医学各论I：心血管活动调节

1、Regulation of Cardiovascular Activities Lecture OutlineNervous RegulationHumoral RegulationAutoregulationNervous RegulationInnervation of the heart Cardiac sympathetic nerve Cardiac vagus nerve1. 起源origin2. 节前纤维preganglionic fiber3. 外周神经节ganglion4. 节后纤维postganglionic fiber5. 支配distribution6. 递质neuro

2、transmitterCardiac 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Cardiac mechanisms of norepinephrineMechanisms of norepinephrine increase Na+ & Ca2+ permeability If , phase 4 spontaneous depolarization, autorhythmicity C

3、a2+ influx (ICa,L) , phase 0 amplitude & velocity , conductivity Ca2+ influx (ICa,L) , Ca2+ release , Ca2+ i , contractility (CICR) Asymmetrical innervation of sympathetic nerveCardiac parasympathetic actions Negative chronotropic effect负性变时作用 Negative dromotropic effect负性变传导作用 Negative inotropi

4、c effect负性变力作用Cardiac mechanisms of acetylcholineMechanisms 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 , contr

5、actility Cardiac effect of parasympathetic stimulationVagal ManeuversValsalva 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,

6、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 (1666-1723) who first described the maneuver.Physiological response in Valsalva maneuver The normal ph

7、ysiological response consists of 4 phasesPhysiological response in Valsalva maneuverThe normal physiological response consists of 4 phasesInitial pressure rise: On application of expiratory force, pressure rises inside the chest forcing blood out of the pulmonary circulation into the left atrium. Th

8、is 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 strok

9、e 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.

10、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

11、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 befor

12、e returning to a normal level. With return of blood pressure, the pulse rate returns towards normal. Interaction of sympathetic and parasympathetic nervesPredominance of autonomic nervesTonus紧张 Cardiac vagal tone心迷走紧张 Cardiac sympathetic tone心交感紧张Innervation of the blood vessels Vasoconstrictor nerv

13、e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Cardiovascular CenterA collection of functionally similar neurons that help to regulate HR, SV, and blood vessel

14、 toneVasomotor centerLocated 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 solitariusVasomotor center Reticular su

15、bstance of the pons Mesencephalon Diencephalon Hypothalamus Cerebral cortex CerebellumHigher cardiovascular centersBaroreceptor Reflexes Arterial baroreceptors Carotid sinus receptor Aortic arch receptor Afferent nerves (Buffer nerves) Cardiovascular center: medulla Efferent nerves: cardiac sympathe

16、tic nerve, sympathetic constrictor nerve, vagus nerve Effector: heart & blood vesselsBaroreceptor neurons function as sensors in the homeostatic maintenance of MAP by constantly monitoring pressure in the aortic arch and carotid sinuses. Characteristics of baroreceptors:Sensitive to stretching o

17、f the vessel wallsProportional firing rate to increased stretchingResponding to pressures ranging from 60-180 mmHgReceptors within the aortic arch are less sensitive than the carotid sinus receptorsThe action potential frequency in baroreceptor neurons is represented here as being directly proportio

18、nal to MAP. Baroreceptor neurons deliver MAP information to the medulla oblongatas cardiovascular control center (CVCC);the CVCC determines autonomic output to the heart.i.e., MAP is above homeostatic set point i.e., reduce cardiac output Reflex pathwayClick here to play theBaroreceptor Reflex Contr

19、ol of Blood PressureFlash AnimationTypical carotid sinus reflexMaintaining relatively constant arterial pressure, reducing the variation in arterial pressurePhysiological SignificanceOther Cardiovascular ReflexesClick here to play theChemoreceptor Reflex Control of Blood PressureFlash AnimationHumor

20、al Regulation Vasoconstrictor agents Vasodilator agentsRenin-angiotensin systemJuxtaglomerular cellRenin Constricts resistance vessels Acts upon the adrenal cortex to release aldosterone Stimulates the release of vasopressin Facilitates norepinephrine release from sympathetic nerve endings Stimulate

21、s thirst centers within the brainPhysiological effects of angiotensin IIEpinephrine & NorepinephrineSourcesEpinephrine-adrenal medulla Norepinephrine-adrenal medulla sympathetic nervesCatecholaminesNorepinephrineEpinephrine EffectsEpinephrineNorepinephrineReceptora-adrenoceptor+ +b-adrenoceptor+

22、 +Heartheart rate+ + (in vitro) (in vivo)cardiac output+ Vesselsconstriction (skin, visceral) + +relaxation (SM, liver) +total peripheral resistance +Blood pressuresystolic + +diastolic +MAP + +Clinical applicationpositive inotropic pressor agent agentA 23-year-old woman presents to your emergency s

23、ervice 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 98.7F. She is immediately treated with supplemental oxygen. In treating

24、 this condition further, what drug is required most urgently? A Theophylline B Glucagon C Cimetidine D Methylprednisolone E Epinephrine Vasopressin (antidiuretic hormone, ADH)Endothelium-derived vasoactive substancesVasodilator factors PGI2-prostacyclin EDRF, NO-endothelium-derived relaxing factor,

25、nitric oxide EDHF-endothelium-dependent hyperpolarizing factorVasoconstrictor factors EndothelinAtrial natriuretic peptide (ANP)Produces natriuresis and diuresis Decreases renin releaseReduces total peripheral resistance via vasodilatationDecreases heart rate, cardiac outputAutoregulationDefinition:

26、 Intrinsic ability of an organ to maintain a constant blood flow despite changes in perfusion pressure, independent of any neural or humoral influencesMyogenic mechanismThe myogenic mechanism is how arteries and arterioles react to an increase or decrease of blood pressure to keep the blood flow wit

27、hin the blood vessel constantThe smooth muscle of the blood vessels reacts to the stretching of the muscle by opening ion channels, which cause the muscle to depolarize, leading to muscle contraction. This significantly reduces the volume of blood able to pass through the lumen, which reduces blood flow through the blood vessel. Alternatively when the smooth muscle in the blood vesse