Hypertension Physiology Lecture Notes PDF

Lecture #31: Hypertension Physiology Julia Hum, PhD Primary Course Instructor Course Meets: Monday/Wednesday/Friday: 2:00-2:50pm Office Hours: Monday/Wednesday/Friday 11:00am-12:00pm (317B or WebEx)  L31: Learning Obje...

Lecture #31: Hypertension Physiology Julia Hum, PhD Primary Course Instructor Course Meets: Monday/Wednesday/Friday: 2:00-2:50pm Office Hours: Monday/Wednesday/Friday 11:00am-12:00pm (317B or WebEx)  L31: Learning Objectives 1. Define the major factors influencing blood pressure 2. Differentiate the sensors that aid in arterial pressure control 3. How do the cardiovascular control centers aid in the maintenance of arterial pressure control? 4. Diagram the steps of the baroreceptor reflex and the RAAS 5. Compare and contrast the short- and long-term mechanisms for controlling blood pressure 6. Diagram the response of the sympathetic nervous system and RAAS to changes in blood pressure 7. Define hypertension and describe general treatment strategies Unless otherwise noted, figures in today’s lecture are from: Lippincott Illustrated Reviews: Physiology 1e Wilson (Ch. 20) L31: “Take Home” Slide  Major Factors Influencing Blood Pressure L31 Vocab: MAP CO SVR Preload Inotropy LO1  Arterial Pressure Control CV system includes two pathways for monitoring and maintaining arterial pressure 1. Baroreceptor reflex (baroreflex) - simple feedback loop = short-term Sensors Integrator Effectors 2. Mean arterial pressure (MAP) – complex feedback loop = long-term Changes in circulating blood volume by modifying renal function LO5  Arterial Pressure Control: Sensors Three Main Sensors provide the brainstem with information on pressure and flow in CV system 1. Arterial Baroreceptors 2. Cardiopulmonary Receptors 3. Chemoreceptors – will cover during pulmonary section LO2  Arterial Pressure Control: Sensors 1. Arterial Baroreceptors Bare sensory nerve endings Cranial nerves buried in elastic fibers of aorta and carotid sinus Increases in MAP – walls of aorta and carotid expand Stretch the nerve endings Sensitivity varies, allowing responsiveness over a wide pressure range LO2  Arterial Pressure Control: Sensors 2. Cardiopulmonary Receptors Baroreceptors in regions on CV Provide fullness indication Found in walls of vena cava, pulmonary artery and vein, and the atria Relay information back to CNS via vagal nerve trunk LO2  Central Integrator: Medulla Oblongata Sensory afferents converge on the medulla oblongata Preset arterial pressure are compared with current state and decisions are made about compensatory response “Cardiovascular Center” 1. Vasomotor center – vasocontriction when active 2. Cardioacceleratory center – increases HR and myocardial contraction when active 3. Cardioinhibitory center – slows HR when active LO3  Central Integrator: Medulla Oblongata Sensory afferents converge on the medulla oblongata Preset arterial pressure are compared with current state and decisions are made about compensatory response LO3  Baroreceptor reflex – short term fix LO4,5  Baroreceptor reflex – short term fix LO4,5  MAP: Long-term Control Pathways Require 24-48 hrs to become fully effective Pathways converge on kidneys Control blood pressure via vascular fullness – “circulating blood volume” Regulation of water output and intake Regulation of Na+ levels: governs how water is partitioned between intracellular and extracellular compartments LO4,5  MAP: Long-term Control Pathways Renin-Angiotensin-Aldosterone-System (RAAS) LO4,5  Response of Sympathetic NS to changes in a Decrease in Blood Pressure DECREASE in BP INCREASE in BP LO4,5  Response of Sympathetic NS to changes in a Decrease in Blood Pressure LO6  Hypertension: Treatment Strategies Goal: reduce cardiovascular and renal morbidity and mortality Current recommendations: Start monotherapy (thiazide diuretic, ACE inhibitor, ARB, or calcium channel blocker) if >130/80 Still uncontrolled: add additional drug, selected based on minimizing adverse effects to reach goal BP If >160/100: dual therapy should be started LO7  Summary of Antihypertensive Drugs **We’ll only be covering a subset of these on Wednesday**  What is Hypertension? Blood Pressure Categories in Adults (Current Guidelines) Systolic Diastolic Category (mmHg) (mmHg) Normal < 120 and < 80 Elevated 120 – 129 and < 80 Hypertension Stage 1 130 – 139 or 80 – 89 Stage 2 ≥ 140 or ≥ 90 American Heart Association and the American College of Cardiology, published new guidelines LO7 in November 2017 for defining and treating hypertension.  How Does Hypertension Occur? Most hypertension occurs secondary to other diseases +90% of patients have ”essential hypertension” Known influences: family history, age, race, education, income, diet, stress LO7  Factors Tipping the Scale Towards Hypertension LO7