Local_and_Humoral_Control_of_Tissue_Blood_Flow_2023 (1).pptx

Local Control of the Resistance Vasculature and Microcirculation Joseph N. Benoit, Ph.D. Professor of Physiology Source Text • Guyton & Hall Textbook of Medical Physiology, 14th Edition • Chapter 17: Local and Humoral Control of Tissue Blood Flow Session Objectives Describe the difference betwe...

Local Control of the Resistance Vasculature and Microcirculation Joseph N. Benoit, Ph.D. Professor of Physiology Source Text • Guyton & Hall Textbook of Medical Physiology, 14th Edition • Chapter 17: Local and Humoral Control of Tissue Blood Flow Session Objectives Describe the difference between extrinsic and intrinsic control of organ blood flow. Differentiate between acute and long term control of blood flow to an organ. Define metabolic regulation of blood flow. Explain the vasodilator theory and oxygen (nutrient) demand theories of metabolic control. Describe how the theory of metabolic regulation of blood flow accounts for active hyperemia and reactive hyperemia. Define myogenic regulation of blood flow. Describe the contribution of myogenic tone to blood flow regulation. Define autoregulation of blood flow. Distinguish between short-term and long-term autoregulatory responses and the mechanisms responsible for each. Identify the role of PO2, PCO2, pH, adenosine, and K+ in the metabolic control of blood flow to specific tissues. Diagram the synthetic pathway for nitric oxide (i.e., Endothelial Derived Relaxing Factor [EDRF]), including substrate and the interplay between endothelium and vascular smooth muscle. Discuss the importance of endothelin as an endothelial derived constrictor substance. Describe the role of major vascular reactive hormones and autocoids in the regulation of blood flow.. Explain how changes in the balance of cAMP, cGMP, cytosolic Ca2+, IP3, and pressure can influence vascular resistance to an organ. Tissue Specific Needs for Blood Flow Oxygen delivery Nutrient Supply Carbon dioxide removal Hydrogen ion removal Maintenance of ionic balance Delivery of hormones and other substances to tissue Mechanisms of Blood Flow Control Acute Control • Rapid Changes in Arterioles, metarterioles, precapillary sphincters that occur over seconds to minutes Chronic Control • Slow controlled changes over days, weeks, or Acute Control of Blood Flow • Increases in Tissue Metabolism Increase Tissue Blood Flow • Reduced Oxygen Availability Increases Tissue Blood Flow Metabolic Control of Blood Flow • Vasodilator Theory • Oxygen Demand Theory Special Examples of Metabolic Control • Reactive Hyperemia • Active Hyperemia Myogenic Regulation Autoregulation Control of Tissue Blood Flow by Endothelium Derived Relaxing or Constricting Factors • Nitric Oxide • Prostaglandins • Endothelin Kidneys Special Mechanisms for Acute Blood Flow Control in Specific Tissues • Tubuloglomerular Feedback Brain • CO2 and H+ Skin • Body Temperature Local Changes in Vascular Resistance Can Affect Capillary Pressure Long-Term Blood Flow Regulation Blood Flow Regulation by Changes in Tissue Vascularity Vascular Remodeling • Inward Eutrophic Remodeling • Hypertrophic Remodeling • Outward Hypertrophic Remodeling Humoral Control of the Circulation Vasoconstrictors • Norepinehrine & Epinephrine • Angiotensin II • Vasopressin Vasodilators • Kinins • Bradykinin • Histamine Calcium ions Vascular Control by Ion Channels and Other Chemical Factors Potassium ions Magnesium ions Hydrogen ions Anions (Acetate & Citrate) Carbon dioxide Blood Flow to and Organ is Dependent on the Balance of Numerous Factors that Influence Vascular Smooth Muscle Signal Transduction The End!