Presentation on theme: "CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION"— Presentation transcript:
1CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION DR SYED SHAHID HABIBMBBS DSDM FCPSAssociate ProfessorDept. of PhysiologyCollege of Medicine & KKUH
2At 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
3120 mm Hg Systolic blood pressure (120 mm Hg) Maximum pressure exerted in the arterieswhen blood is ejected into themduring systole120 mm Hg(120 mm Hg)
480 mm Hg Diastolic blood pressure (80 mm Hg) Minimum pressure within the arterieswhen blood is drained off from themduring diastole80 mm Hg(80 mm Hg)
5systolic and diastolic pressures Pulse pressureThe differencebetweensystolic and diastolic pressures40 mm Hg( = 40 mm Hg)
693 mm Hg Mean Arterial Pressure 80 + 13 = 93 mm Hg Average pressure which drives bloodforward into the tissuesdiastolic pressure + (1/3 (systolic - diastolic pressure)= 93 mm Hg
7Arterial blood pressure Blood pressure is the force the blood exerts againstthe walls of the blood vesselsSystolicpressureMaximum pressure during systole120mmHgDiastolicpressureMinimum pressure during diastole80 mmHgPulsepressureSystolic pressure diastolic pressure40 mmHgSBP is dependant on CO and DBP is dependant on TPR. TPR is responsible for DBP and forward flow of bloodMeanpressureDiastolic pressure (1/3 pulse pressure)93 mmHgMean arterial pressure is the main driving force for blood flow
8 B e c a u s e Mean arterial pressure 100 mm Hg 93 mmHg The duration ofsystole is shorterthan thatof the diastoleMean pressure is the average pressure during cardiac cycle
9Normal Variations Age Sleep Posture Exercise SBP increases and DBP is mantained in mild to moderate. (Therefore DBP is more imp)Gravity
10Effect of GravityThe pressure in any vessel below heart level is increased and above heart level is decreased by the effect of gravity.The magnitude of the gravitational effect is 0.77 mm Hg/cm of vertical distance above or below the heart at the density of normal blood.In an adult human in the upright position, when the mean arterial pressure at heart level is 100 mm Hg, the mean pressure in a large artery in the head (50 cm above the heart) is 62 mm Hg (100 – [0.77 x 50])and the pressure in a large artery in the foot (105 cm below the heart) is 180 mm Hg (100 + [0.77 x 105]).The pressures in Figure 32–28 are those in blood vessels at heart level. The pressure in any vessel below heart level is increased and that in any vessel above heart level is decreased by the effect of gravity. The magnitude of the gravitational effect is 0.77 mm Hg/cm of vertical distance above or below the heart at the density of normal blood. Thus, in an adult human in the upright position, when the mean arterial pressure at heart level is 100 mm Hg, the mean pressure in a large artery in the head (50 cm above the heart) is 62 mm Hg (100 – [0.77 x 50]) and the pressure in a large artery in the foot (105 cm below the heart) is 180 mm Hg (100 + [0.77 x 105]). The effect of gravity on venous pressure is similar (Figure 32–30).
11Factors Determining Blood Pressure Determining word means why there is BP, Why SBP and DBP
12 MAP CO TPR P F = --------------- R Ohm’s Law F = Cardiac output (CO) P = Mean arterial pressure (MAP)R = Total peripheral resistance (TPR)MA P CO = TP R MAP CO TPR
13 Heart rate (chronotropic effect) CO = SV X HR Plasma epinephrine Activity ofsympatheticnerves to heart Activity ofparasympatheticnerves to heart Heart rate (chronotropic effect)
14 End-diastolic ventricular volume Activity ofsympatheticnerves to heart PlasmaepinephrineForce of Contraction (Inotropic Effect) Stroke volume
15 P r4 Q = --------------------- 8 L Poiseuille’s Law P r4 Q = LQ = Flow P = Pressure gradientr = Radius = ViscosityL = Length of tube/8 = ConstantMax is in arterioles because of max smooth Ms and rich innervation by sympathetic
16Length of the blood vessels remains unchangedViscosity of bloodusually varies little
17Total peripheral resistance Major controllingfactorBloodviscosityArteriolarradiusElastcicityRBC, PLASMA PROTEINS (Albumin), Eg Polycythemia viscosit is high so high DBP and in Anemia SBP is highPlasmaProteinsNo. ofRBC
18Elasticity depends on kinetic energy and PE Elasticity depends on kinetic energy and PE. KE is responsible for expansion of Arterial Wall While PE is responsible for elastic recoil.
20Radius of the blood vessel The major determinantof resistance and blood flow isthe 4th power of theRadius of the blood vesselR r4Resistance varies inversely with the caliber of the blood vessel
21Q P 50 mm Hg 10 mm Hg A 90 mm Hg 10 mm Hg B Flow in vessel B is two times the flow in vessel Abecause the P is two times more in vessel B
22Relationship of flow & radius Blood vessel - 1Blood vessel - 2(radius 2 the radius of vessel - 1Flow = 1 ml / min.Relationshipofflow & radiusBlood vessel - 3(radius 3 the radius of vessel - 1Flow = (2 2 2 2) 16 ml / min.Flow = (3 3 3 3) 81 ml / min.
23directly and resistance Flow variesdirectly and resistanceinversely with the 4thpower of the radiusIncreasein radius by two timesdecreases resistanceby 16th timeIncreasein radius by two timesincreases blood flowby 16 times
25The pressure falls rapidly in the arterioles The magnitude of this pressure drop depends uponthe degree of arteriolar constriction or dilatation
26BLOOD PRESSURE REGULATING MECHANISMS Short Term (Within few seconds)Intermediate (Within few hours)Long Term (Within few days)
27VASOMOTOR CENTER (Area!) 1. Vasoconstrictor area2. Vasodilator area3. Sensory area
28VASOMOTOR CENTER (Area!) 1. A vasoconstrictor area located bilaterally in the anterolateral portions of the upper medulla. exite vasoconstrictor neurons of the sympathetic nervous system.2. A vasodilator area located bilaterally in the anterolateral portions of the lower half of the medulla. inhibit the vasoconstrictor area, thus causing vasodilation.3. A sensory area located bilaterally posterolateral portions of the medulla and lower pons (tractus solitarius). Receive sensory nerve signals by vagus and glossopharyngeal nerves and output control activities of both 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
29in 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.
35Baroreceptor Reflex Mediated Quick operation through (within few autonomic nervesQuick operation(within fewseconds)Influencesheart &blood vesselsAdjusts CO &TPRto restore BPto normal
36Renal 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
37Components 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
39Vasomotor 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
40Stimulus 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
42? ? !! 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??!!
43Pressure on the carotid sinus, produced, for example by the tight collar or carotid massagecancausemarkedbradycardiavasodilatationFaintingor syncope
44Transient loss of consciousness SyncopeTransient loss of consciousnessAssociatedwithAbrupt vasodilatationInadequate cerebral blood flowHypotension and bradycardia
52Two 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.
53Increased Fluid Volume Can Elevate Arterial Pressure by Increasing Cardiac Output orTotal Peripheral Resistance
58ACE 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.