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CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION

CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION. OBJECTIVES. Define blood pressure and Mean Arterial Pressure (MAP) List the factors affecting MAP Describe Short term and long term control of Blood Pressure. At the end of this lecture you should be able to.

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CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION

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  1. CARDIOVASCULAR PHYSIOLOGY BLOOD PRESSURE AND ITS REGULATION

  2. OBJECTIVES • Define blood pressure and Mean Arterial Pressure (MAP) • List the factors affecting MAP • Describe Short term and long term control of Blood Pressure At the end of this lecture you should be able to

  3. BLOOD PRESSURE REGULATING MECHANISMS Short Term (Nervous System works within few seconds) Baroreceptors Chemoreceptors CNS Ischemic Response Long Term (Renal Control works within few days) Intermediate (Within few hours) Stress relaxation Capillary fluid shift

  4. VASOMOTOR CENTER (Area!) 1. Vasoconstrictor area 2. Vasodilator area 3. Sensory area

  5. VASOMOTOR 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 arealocated 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 reflex

  6. Continuous Partial Constriction of the Blood Vessels Is Normally Caused by Sympathetic Vasoconstrictor Tone.

  7. CONTROL OF VMC Reticular Substance of Brain Stem Hypothalamus Posterolateral portions Cause Excitation. Anterior part can cause Excitation or Inhibition Cerebral Cortex Motor Cortex Cause Excitation

  8. Control of blood pressure Short-term Control Long-term control Baroreceptor reflex Renal compensation

  9. Baroreceptors

  10. Baroreceptor Reflex Mediated through autonomic nerves Quick operation (within few seconds) Influences heart & blood vessels Adjusts CO &TPR to restore BP to normal

  11. Renal Control It is perfect 100 % Mediated through Kidneys Renin Angiotensin aldosterone mechanism, Slow operation (within hours to Days) Adjusts urinary output and TPR to restore BP to normal Influences Kidneys & blood vessels

  12. Components Of Baroreceptor Reflex Arc Receptors Baroreceptors in carotid sinuses & arch of aorta Afferents Carotid sinus nerves & nerve from arch of aorta Center Vasomotor Center in medulla oblongata Efferents Sympathetic & parasympathetic nerves Effectors Heart and blood vessels Carotid sinus nerve runs along with glossopharyngeal nerve Aortic nerve runs along with vagus nerve

  13. COMPONENTS OF BARORECEPTOR REFLEX ARC

  14. Heart rate and force of contraction and Vasodilatation  BP Stimulus Increase in BP Receptors Baroreceptors Increase Firing ofGlossopharyngeal and Vagus Nerves Afferents Vasomotor Center in medulla oblongata Center Sympathetic & parasympathetic firing Efferents Heart and blood vessels Effectors Effects

  15. Heart rate and force of contraction and Vasoconstriction  BP Stimulus Decrease in BP Receptors Baroreceptors Minimal Firing ofGlossopharyngeal and Vagus Nerves Afferents Vasomotor Center in medulla oblongata Center  Sympathetic &  parasympathetic firing Efferents Heart and blood vessels Effectors Effects

  16. Baroreceptor reflex  MAP Baroreceptor reflex  Firing of baroreceptors  Sympathetic tone  Vagal tone Vasodilatation  HR  SV  TPR  Cardiac output  MAP

  17. What shall be the effect of bilateral clamping of the carotid arteries proximal to the carotid sinuses? ? OR Can you guess ! Rise in blood pressure and heart rate. Because the inhibitory control of sympathetic is gone What shall be the effect of bilateral cutting of the carotid sinus nerves? ? !!

  18. Pressure on the carotid sinus, produced, for example by the tight collar or carotid massage can cause marked bradycardia vasodilatation Fainting or syncope

  19. Syncope Transient loss of consciousness Associated with Abrupt vasodilatation Inadequate cerebral blood flow Hypotension and bradycardia

  20. Pressure “Buffer” Function of the Baroreceptor Control System.

  21. Pressure “Buffer” Function of the Baroreceptor Control System.

  22. COTROL OF ARTERIAL PRESSURE IS ALSO BY Chemoreceptors (Carotid and Aortic Bodies) Atrial and Pulmonary Artery Reflexes (Low Pressure Receptors) CNS Ischemic Response

  23. Pressure Natriuresis and Pressure Diuresis

  24. Increased Fluid Volume Can Elevate Arterial Pressure by Increasing Cardiac Output or Total Peripheral Resistance

  25. Salt (NaCl) intake & Arterial Pressure Regulation

  26. Renal control  MAP  Renin secretion Angiotensinogen Angiotensin I ACE in Lungs Angiotensin II Vasoconstriction Salt & water Retention  TPR  ECF Volume  MAP

  27. ACE synthesize Ang II (Vascoconstrictor) and Inactivates Bradykinin (Vasodilator)

  28.  MAP  MAP Renal control of blood presure  Urine formation  Cardiac output  Blood volume  Stroke volume  venous return  EDV

  29. THANKS

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