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Regulation of blood pressure

Regulation of blood pressure through renal, baro-receptor and chemoreceptors mechanisms

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Regulation of blood pressure

  1. 1. Presented To: Ms. Komal Najam Presented by: Ali Mansoor Abdullah Yaqoob Harry Hamid
  2. 2.  Arterial Blood-Pressure a. Definition b. Regulation  Mechanisms of B.P Regulation  Nervous mechanism for B.P regulation a. Baro-receceptor Mechanism b. Chemoreceptor mechanism  Renal mechanism for B.P regulation  Hormonal Mechaism  Local Mechanism  Reflexes and Responses  Marey Reflex  Atrium-brainbridge Reflex  Bezold-Jarisch Reflex
  3. 3. Definition: • Arterial blood pressure is defined as the lateral pressure exerted by the column of blood on wall of arteries. • LOCAL FACTORS DETERMINIG THE ARTERIAL BLOOD PRESSURE
  4. 4. There are four mechanisms for regulation of the blood pressure. 1. Nervous mechanism or shortterm regulatory mechanism 2. Renal mechanism or longterm regulatory mechanism 3. Hormonal mechanism 4. Local mechanism.
  5. 5. • Most rapid among all the mechanisms • It operates through the vasomotor system. Vasomotor System Vasomotor system includes three components: 1. Vasomotor center (control heart rate) 2. Vasoconstrictor fibers (vasoconstriction) 3. Vasodilator fibers (vasodilation) (Receives impulses from Baroreceptors & Chemoreceptors.)
  6. 6. Rise in B.P activation of impulses to nucleus baroreceptors of tractus solitarius nucleus of Reduces vasomotor inhibition of tractus solitarius acts . tone vasoconstrictor area on vasomotor center excites vasodilator area Redution in peripheral resistance Blood- & Vasodilatation occur pressure decreases (force of contraction & Cardiac output decrease)
  7. 7. 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 and total peripheral resistance Blood pressure increased toward normal
  8. 8. Decreased blood pressure Decreased flow of blood Decrease in O2 & Increase in CO2 Excitation in the chemoreceptors Send impulses to vasoconstrictors Blood pressure rises and blood flow increases
  9. 9. • Long term regulation of Arterial B.P • Renal Mechanism works even when nerous mechanism adapts to the new pressure. • Two ways of regulation of B.P 1. By regulation of ECF volume 2. Through reninangiotensin mechanism.
  10. 10. Increase in excretion of water excretion of salts (sodium) B.P (pressure diuresis) (Pressure Natriuresis) Blood pressure decrease in blood decrease in ECF restored volume volume
  11. 11. Decrease in reabsorption Increase in ECF B.P from & Blood renal-tubules volumes Blood pressure Increase in cardiac Restored output
  12. 12. Renin along with Angiotensin forms Renin- Angiotensin system, which is a hormone system that plays an important role in the maintenance of blood pressure Renin - J.G Cells of Kidney Angiotensinogen - Liver Cells ACE - Lungs
  13. 13. • Local mechanism regulates blood pressure by Vasoconstriction & vasodilatation. Local vasoconstrictors • Are also called EDCF (endothelium derived constricting factors) as they are derived from vascular endothelium. • Common EDCF are ET1, ET2 & ET3. • Produced by stretching of blood vessels & cause vasoconstriction.
  14. 14. Vasodilators of metabolic origin: carbon monoxide, lactate, H+ & adenosine. Vasodilators of Endothelial origin: • Nitroxides • NO3 (nitrate) • NO+ (nitrosonium ion) • NO- (nitroxyl anion)
  15. 15. • Vasomotor center regulates the cardiac activity by receiving impulses from different sources in the body. After receiving the impulses from different sources, the vasodilator area alters the vagal tone and modulates the activities of the heart. • Various sources from which the impulses reach the vasomotor center: 1. IMPULSES FROM BARORECEPTORS – MAREY REFLEX 2. IMPULSES FROM RIGHT ATRIUM – BAINBRIDGE REFLEX 3. BEZOLD-JARISCH REFLEX
  16. 16. • Baroreceptors regulate the heart rate through Marey reflex. Stimulus for this reflex is increase in blood pressure. • Marey reflex is a cardioinhibitory reflex that decreases heart rate when blood pressure increases. • Whenever blood pressure increases, the aortic and carotid baroreceptor are stimulated. • stimulatory impulses are sent to nucleus of tractus solitarius via Hering nerve and aortic nerve. • then nucleus of tractus solitarius stimulates vasodilator area and increase the vagal tone leading to decrease the heart rate
  17. 17. • Bainbridg reflex is a cardio accelerator reflex. • Increases the heart rate when venous return is increased. • This reflex rises from right atrium it right atrial reflex. • Increase in venous return causes distention of right atrium and stimulation of stretch receptors, situated in the wall of right atrium. • Stretch receptors, in turn, send nerve to vasodilator area of vasomotor center. Vasodilator area is inhibited, resulting in decrease in vagal tone and increase in heart rate.
  18. 18. • This is also called coronary chemoreceptors. • Bezold- Jarisch reflex is a pathological reflex and it does not occur in physiological conditions. • Conditions when Bezold-Jarisch Reflex Occurs. 1. Myocardial infarction 2 .Administration of thrombolytic agents 3. Hemorrhage 4. Aortic stenosis 5. Syncope.
  19. 19. • Hypertension • Hypotension • Hypertention; when sistolic pressure remain elevated above 150 mm Hg and distolic pressure remains 90 mm Hg is called hypetrtention. • Hypotention;when the sistolic pressure less then 90 mm Hg is called hypotention.