2CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION
3At the end of this lecture you should be able to OBJECTIVESAt the end of this lecture you should be able toDefine blood pressure and Mean Arterial Pressure (MAP)List the factors affecting MAPDescribe Short term and long term control of Blood Pressure
4BLOOD PRESSURE REGULATING MECHANISMS Short Term (Nervous System works within few seconds)BaroreceptorsChemoreceptorsCNS Ischemic ResponseLong Term (Renal Control works within few days)Intermediate (Within few hours)Stress relaxationCapillary fluid shift
5VASOMOTOR CENTER (Area!) 1. Vasoconstrictor area2. Vasodilator area3. Sensory area
6VASOMOTOR CENTER (Area!) 1. A vasoconstrictor area located bilaterally in upper medulla. excite vasoconstrictor neurons of the sympathetic nervous system.2. A vasodilator area located bilaterally in the lower half of the medulla. inhibit the vasoconstrictor area, thus causing vasodilation.3. A sensory area located bilaterally in medulla and pons (tractus solitarius). Receive sensory nerve signals from vagus and glossopharyngeal nerves and output control the vasoconstrictor and vasodilator areas An example is the baroreceptor reflexNervous Regulation of CirculationThe Autonomic Nervous SystemSympathetic Vasoconstrictor Tone (Vasomotor Tone)Control of Vasomotor CenterBaroreceptor Control System
7in mosttissues all the vessels except the capillaries, precapillary sphincters, and metarteriolesare innervated.Continuous Partial Constriction of the Blood Vessels Is Normally Caused by Sympathetic Vasoconstrictor Tone.
8CONTROL OF VMC Reticular Substance of Brain Stem Hypothalamus Posterolateral portions CauseExcitation. Anterior part can causeExcitation or InhibitionCerebral CortexMotor Cortex Cause Excitation
12Baroreceptor Reflex Mediated Quick operation through (within few autonomic nervesQuick operation(within fewseconds)Influencesheart &blood vesselsAdjusts CO &TPRto restore BPto normal
13Renal Control It is perfect 100 % Mediated through Kidneys Renin Angiotensinaldosterone mechanism,Slow operation(within hours to Days)Adjusts urinary output and TPRto restore BPto normalInfluencesKidneys &blood vessels
14Components Of Baroreceptor Reflex Arc ReceptorsBaroreceptors in carotid sinuses & arch of aortaAfferentsCarotid sinus nerves & nerve from arch of aortaCenterVasomotor Center in medulla oblongataEfferentsSympathetic & parasympathetic nervesEffectorsHeart and blood vesselsCarotid sinus nerve runs along with glossopharyngeal nerveAortic nerve runs along with vagus nerve
16Vasomotor Center in medulla oblongata Heart and blood vessels StimulusIncrease in BPReceptorsBaroreceptorsIncrease Firing of Glossopharyngeal and Vagus NervesAfferentsVasomotor Center in medulla oblongataCenter Sympathetic & parasympathetic firingEfferentsHeart and blood vesselsEffectorsHeart rate and force of contractionand Vasodilatation BPEffects
17Stimulus Receptors Afferents Center Efferents Effectors Effects Decrease in BPReceptorsBaroreceptorsMinimal Firing of Glossopharyngeal and Vagus NervesAfferentsVasomotor Center in medulla oblongataCenter Sympathetic & parasympathetic firingEfferentsHeart and blood vesselsEffectorsHeart rate and force of contractionand Vasoconstriction BPEffects
19? ? !! OR Can you guess ! Because the inhibitory What shall be the effect of bilateralclamping of the carotid arteriesproximal to the carotid sinuses??ORRise in blood pressureand heart rate.Because the inhibitorycontrol of sympatheticis goneCan youguess !What shall be the effect ofbilateral cutting of thecarotid sinus nerves??!!
20Pressure on the carotid sinus, produced, for example by the tight collar or carotid massagecancausemarkedbradycardiavasodilatationFaintingor syncope
21Transient loss of consciousness SyncopeTransient loss of consciousnessAssociatedwithAbrupt vasodilatationInadequate cerebral blood flowHypotension and bradycardia
28Two ways in which the arterial pressure can be increased: A, by shifting the renal output curve in the right-hand direction towarda higher pressure level or B, by increasing the intake level of saltand water.
29Increased Fluid Volume Can Elevate Arterial Pressure by Increasing Cardiac Output orTotal Peripheral Resistance
34ACE synthesize Ang II (Vascoconstrictor) and Inactivates Bradykinin (Vasodilator) Two related vasodilator peptides called kinins are found in the body. One is the nonapeptide bradykinin, and the other is the decapeptide lysylbradykinin, also known as kallidin (Figure 33–11). Lysylbradykinin can be converted to bradykinin by aminopeptidase. Both peptides are metabolized to inactive fragments by kininase I, a carboxypeptidase that removes the carboxyl terminal arginine (Arg). In addition, the dipeptidylcarboxypeptidase kininase II inactivates bradykinin and lysylbradykinin by removing phenylalanine-arginine (Phe-Arg) from the carboxyl terminal. Kininase II is the same enzyme as angiotensin-converting enzyme (see Chapter 39), which removes histidine-leucine (His-Leu) from the carboxyl terminal end of angiotensin I.