REGULATION OF ARTERIAL BLOOD PRESSURE TERMS SBP DBP

REGULATION OF ARTERIAL BLOOD PRESSURE

TERMS • SBP • DBP • PP • MAP

PHYSIOLOGICAL VARIATIONS • • • AGE SEX BODY BUILT RACE DIURNAL VARIATIONS • POSTURE • AFTER MEALS • DURING SLEEP • AFTER EXERCISE • EMOTIONAL CONDITIONS

DETERMINANTS OF ARTERIAL BLOOD PRESSURE • AP = CO x TPR • CO = SV x HR • SV = EDV ( – ) ESV

DETERMINANTS OF ARTERIAL BLOOD PRESSURE

REGULATION OF ARTERIAL BLOOD PRESSURE Regulation of Blood Pressure Nervous Mechanism Renal Mechanism Hormonal Mechanism Local Mechanism By Vasomotor Center and Impulses from Periphery By Regulation of ECF Volume and renin – angiotensin mechanism By Vasocons-trictor and Vasodilator Hormones By Local Vasocons-trictors and Vasodilators

REGULATION OF ARTERIAL BLOOD PRESSURE • SHORT-TERM CONTROL (IN SEC – MIN) • INTERMEDIATE-TERM CONTROL (30 MIN – HOURS) • LONG – TERM CONTROL

SHORT-TERM CONTROL OF AP • CNS ISCHAEMIC RESPONSE • BARORECEPTOR REFLEX • CHEMORECEPTOR REFLEX

CUSHING REFLEX Gross hypotension or increased ICP Decreased cerebral blood flow or decreased blood flow to VMC Hypoxia and hypercapnia at VMC Strong stimulation of VMC Intense vasoconstriction Increased pressure in carotid sinus Activation of baroreceptor reflex Reflex bradycardia

REGULATION OF BLOOD PRESSURE BY BARORECEPTOR MECHANISM Increase in Blood Pressure Stimulation Baroreceptors Impulses via IX and X Cranial Nerves Normal Blood Pressure Dilatation of blood vessels Bradycardia and reduction in cardiac output Decrease in vasomotor tone Increase in vagal tone Inhibition of vasoconstrictor area Stimulation of vasodilator area Nucleus of tractus solitarius

BARORECEPTOR REFLEXES TO RESTORE BLOOD PRESSURE TO NORMAL When blood pressure becomes elevated above normal Carotid sinus and aortic arch receptor potential Cardiovascular center Rate of firing in afferent nerves Sympathetic cardiac nerve activity and Sympathetic vasoconstrictor nerve activity and Parasympathetic nerve activity Heart rate and stroke volume and arteriolar and venous vasodilation Cardiac output Blood pressure decreased toward normal and total peripheral resistance

BARORECEPTOR REFLEXES TO RESTORE BLOOD PRESSURE TO NORMAL When blood pressure falls below normal Carotid sinus and aortic arch receptor potential Cardiovascular center Rate of firing in afferent nerves Sympathetic cardiac nerve activity and sympathetic vasoconstrictor nerve activity and parasympathetic nerve activity Heart rate and stroke volume and arteriolar and venous vasoconstriction Cardiac output Blood pressure increased toward normal and total peripheral resistance

BARORECEPTOR REFLEX

CHEMORECEPTOR REFLEX

INTERMEDIATE CONTROL OF AP • RENIN - ANGIOTENSIN – VASOCONSTRICTOR MECH. • STRESS RELAXATION OF VASCULATURE • FLUID – SHIFT THROUGH THE CAPILLARY WALL

REGULATION OF BLOOD PRESSURE BY RENINANGIOTENSIN MECHANISM Decrease in Blood Pressure Normal Blood Pressure Stimulation Juxtaglomerular apparatus Renin Angiotensinogen Angiotensin I Converting enzyme Angiotensin II Vasoconstriction

SITES OF PRODUCTION Renin - J. G Cells of Kidney Angiotensinogen - Liver Cells ACE Lungs -

LONG – TERM CONTROL OF AP • RENAL FLUID SHIFT (THROUGH ADH / VOLUME RECEPTORS) • RENIN – ANGIOTENSIN – ALDOSTERONE MECH.

RESTORATION OF FLUID VOLUME OF THE BODY BY ADH IN VOLUME DEPLETION STATE. [NTS: NUCLEUS TRACTUS SOLITARIOUS]

Sequential events by which increased salt intake increases the arterial pressure. Increased salt intake Increased extracellular volume Increased arterial pressure Decreased renin and angiotensin Decreased renal retention of salt and water Return of extracellular volume almost to normal Return of arterial pressure almost to normal

LOCAL MECH. FOR CONTROL OF AP A. Vasodilatos 1. EDRF 2. Bradykinin 3. Histamine 4. ANP 5. VIP 6. Substance P 7. Prostacyclin 8. Adenosine + 9. K 10. Acidosis [ CO 2] 11. Hypercapnia 12. Hypoxia 13. Temperature

B. Vasoconstrictors 1. 2. 3. 4. 5. 6. 7. 8. Endothelin-1 Angiotensin II Norepinephrine ADH Serotonin Thromboxane A 2 Neuropeptide-Y Cold

HORMONAL MECH. FOR CONTROL OF AP • HORMONES RAISING AP – ADRENALINE – NORADRENALINE – THYROXINE – ALDOSTERONE – VASOPRESSIN – ANGIOTENSIN – SEROTONIN

HORMONAL MECH. FOR CONTROL OF AP • HORMONES DECREASING AP – VIP – BRADY KININ – PROSTAGLANDIN – HISTAMINE – ACETYLCHOLINE – ANP

PATHOLOGICAL VARIATIONS • HYPERTENSION • HYPOTENSION