Blood Pressure - Introduction to Human Physiology - Lecture Slides, Slides of Human Physiology

Download Blood Pressure - Introduction to Human Physiology - Lecture Slides and more Slides Human Physiology in PDF only on Docsity! Blood Pressure (BP) • Arterioles play role in blood distribution and control of BP • Blood flow to capillaries and BP is controlled by diameter of arterioles • Capillary BP is decreased because they are downstream of high resistance arterioles Docsity.com Blood Pressure (BP) • Capillary BP is also low because of large total cross-sectional area Docsity.com Atrial Stretch Receptors • Activated by increased venous return and act to reduce BP and in response: 1) Stimulate reflex tachycardia, as a result of increased sympathetic activity 2) Inhibit ADH release – resulting in excretion of larger volumes of urine and lowering of blood volume and 3) Promote secretion of ANP – lowers blood volume by increasing urinary salt and water excretion Docsity.com Measurement of Blood Pressure • Via auscultation – to examine by listening • No sound is heard during laminar flow (normal, quiet, smooth blood flow) • Korotkoff sounds can be heard when sphygmomanometer cuff pressure is greater than diastolic but lower than systolic pressure – Cuff constricts artery creating turbulent flow and noise as blood passes constriction during systole and is blocked during diastole – 1st Korotkoff sound heard at pressure when blood is 1st able to pass thru cuff – Last sound occurs when one can no longer hear systole because cuff pressure = diastolic pressure Docsity.com Measurement of BP • BP cuff is inflated above systolic pressure, occluding artery • As cuff pressure is lowered, blood flows only when systolic pressure is above cuff pressure, producing Korotkoff sounds • Sounds are heard until cuff pressure equals diastolic pressure Docsity.com Essential Hypertension • Increase in peripheral resistance is universal • CO and HR are elevated in many • Secretion of renin, Angio II, and aldosterone is variable • Sustained high stress (increases sympathetic activity) and high salt intake act synergistically in development of hypertension • Prolonged high BP causes thickening of arterial walls, resulting in atherosclerosis • Kidneys appear to be unable to properly excrete Na+ and H2O Docsity.com Dangers of Hypertension • Patients are often asymptomatic until substantial vascular damage occurs – Contributes to atherosclerosis – Increases workload of the heart leading to ventricular hypertrophy and congestive heart failure – Often damages cerebral blood vessels leading to stroke – These are why it is called the "silent killer" Docsity.com Treatment of Hypertension • Includes lifestyle changes such as cessation of smoking, moderation in alcohol intake, weight reduction, exercise, reduced Na+ intake, increased K+ intake • Drug treatments include diuretics to reduce fluid volume, beta-blockers to decrease HR, calcium blockers, ACE inhibitors to inhibit formation of Angio II, and Angio II- receptor blockers Docsity.com Hypovolemic Shock • Circulatory shock caused by low blood volume – e.g. from hemorrhage, dehydration, or burns – Characterized by decreased CO and BP • Compensatory responses include sympathoadrenal activation via baroreceptor reflex – Results in low BP, rapid pulse, cold clammy skin, low urine output Docsity.com Septic Shock • Refers to dangerously low blood pressure resulting from sepsis (infection) • Mortality rate is high (50-70%) • Often occurs as a result of endotoxin release from bacteria – Endotoxin induces NO production causing vasodilation and resultant low BP – Effective treatment includes drugs that inhibit production of NO Docsity.com Other Causes of Circulatory Shock • Anaphylactic shock – severe allergic reaction can cause a rapid fall in BP – Due to generalized release of histamine causing vasodilation • Neurogenic shock – rapid fall in BP – can result from decrease in sympathetic tone following spinal cord damage or anesthesia • Cardiogenic shock – common following cardiac failure – resulting from infarction that causes significant myocardial loss Docsity.com