Blood Pressure Regulation Chapter 13 pages 427 441 and Chapter 14 SAMPLE PROBLEMS HR ACh D EPI I NE I SV I I I TPR D D I VR D I I CO D I I DP D I SP I I I PP I I I 4 Factors Contibuting to Cardiac Output HR SV TPR VR WITH CARDIAC SYMPATHETIC STIMULATION OUTPUT No Change in VR HEART RATE As HR increases Filling Time Decreases Digitalis Decrease HR with no direct action on contractility or SV But as filling time increases EDV increases so SV increases according to WITH SYMPATHETIC CARDIAC OUTPUT E D Vor EDP or Atrial Pressure STROKE VOLUME Venous Return see Fig 13 24 Abdomino Thorasic Respiratory Pump Skeletal Muscle Pump Ventricular Diastole Ventricular Systole Skeletal Muscle Pump Fig 13 23 Total Peripheral Resistance Increased TPR Increased Arterial Pressure Increases work of heart and length of systole esp isovolumetric phase Decrease SV initially and briefly Also increases Arterial Venous P increases amount of blood on venous side Increase VR and CO How do we resolve this apparent conflict problem Depends upon ability of ventricles to increase SV Consider exercise Response to Light Exercise Fig 14 12 Blood Pressure BP expressed in mm Hg BP CO x TPR Pressure measured by baroreceptors Aortic arch Carotid sinus VAGUS NERVE Parasympathetic fibers Baroreceptors from aortic arch Stretch receptors from lungs Atrial Baroreceptors Responses Fig 14 1 BARORECEPTOR NERVE ACTIVITY AP SEC 40 180 MEAN BLOOD PRESSURE mm Hg CHEMORECEPTORS PO2 receptors Carotid and aortic bodies Brain stem medulla Sensitive to dissolved O2 Only important at low PO2 Carbonic Anhydrase CO2 H2O H2CO3 H HCO3 Lungs Kidneys CHEMORECEPTORS CO2 pH AORTIC CAROTID BODIES MEDULLA CO2 H2O H2CO3 H HCO3 AS CO2 INCREASES PLASMA CSF pH DECREASES CO2 DISSOLVES FROM PLASMA INTO CSF ACROSS BLOOD BRAIN BARRIER CO2 H2O H2CO3 H HCO3AS PLASMA CO2 INCREASES PLASMA pH DECREASES CO2 DISSOLVES INTO CSF AND CSF pH DECREASES STIMULATING MEDULLARY RECEPTORS INPUTS Baroreceptors pns Chemoreceptors cns pns Atrial volume receptors Cerebral cortex Vasovagal syncope fainting Corticohypothalamic response Flight or fight response Figure 14 2 Whew Medullary cardiovascular center Vasomotor center Pressor area Cardioinhibitory center Depressor area Pressor or vasomotor center is spontaneously active and always slowed by depressor which is activated by baroreceptors Low BP BRAIN M E D U L L A Decreased Input PRESSOR AREA DEPRESOR AREA BARORECEPTOR SENSORY NERVE HEART RATE 1 STROKE VOLUME 1 TPR 1 vs 2 and muscarinic VR BRAIN M E D U L L A PRESSOR AREA DEPRESOR AREA BARORECEPTOR SENSORY NERVE VAGUS HR m uscarinic BRAIN M E D U L L A CHEMORECEPTORS PRESSOR AREA DEPRESOR AREA BARORECEPTOR SENSORY NERVE HEART RAT E 1 ST ROKE VOLUME 1 VR T PR 1 vs 2 and muscarinic Decreased MAP Fig 14 3 Increased MAP Fig 14 3 Receptor mediated response to hemorrhage Fig 14 5 Receptor mediated response to hemorrhage Fig 14 6 REFLEX RESPONSES VASOVAGAL SYNCOPE FAINTING CORTICOHYPOTHALAMIC DEFENSE REACTION FIGHT OR FLIGHT RENAL CONTROL OF BLOOD VOLUME Mammalian kidneys are designed to reabsorb Na and retain it in body fluids increase Na reabsorption increase water reabsorption increase blood volume RAISE BP ANTIDIURETIC HORMONE VASOPRESSIN or ADH 9 amino acid peptide released from posterior pituitary released in response to elevated plasma lowered BP or lowered blood volume decreased atrial EDV and or decreased baroreceptor distention Normally ADH causes Na and water reabsorption by kidneys to increase blood volume and decrease plasma ADH released in response to low BP and not released when BP is high ATRIAL NATRIURETIC PEPTIDE ANP 28 amino acid peptide hormone released from atrial myocytes muscle cells released in response to distention high atrial EDV due to high BP INHIBITS Na K ATPase in kidney THUS Na AND WATER ARE LOST IN URINE lowering blood volume VOLUME RECEPTORS ATRIAL STRETCH RECEPTORS DECREASE ADH And INCREASE ANP increase urine output and decrease blood volume ATRIAL STRETCH RECEPTORS RESPOND TO INCREASED BV BY RENIN ANGIOTENSIN ALDOSTERONE LOW RENAL BLOOD FLOW 20 OF CO ACTIVATION OF POTENT VASOCONSTRICTOR ANGIOTENSIN Things to Review and Know BP A NGIOTENSINOGEN RENIN A NGIOTENSIN I A CE CONSTRICT PERIPHERA L A RTERIOLES Na EXCRETION A NGIOTENSIN II Fig 18 6 INCREA SED A LDOSTERONE BLOOD VOLUME Table 14 1 Fig 14 7