Vascular 2_2024_Benmerzouga.pptx

Vascular 2-Pre-class PowerPoint Imaan Benmerzouga, Ph.D. March 8 2024 3:00-5:00 PM Master of Science in Foundational and Integrated Medical Sciences Program Spring 2024 Learning Objectives 1.Recognize the structure and function of the vascular system 2.List the local factors that control systemic va...

Vascular 2-Pre-class PowerPoint Imaan Benmerzouga, Ph.D. March 8 2024 3:00-5:00 PM Master of Science in Foundational and Integrated Medical Sciences Program Spring 2024 Learning Objectives 1.Recognize the structure and function of the vascular system 2.List the local factors that control systemic vascular resistance 3.Discuss the neurohumoral factors that affect blood pressure Review -vascular structure 1) shows branching of the cardiovascular system, from left side to right side of heart and back to left. 2) Variation of aggregate cross-sectional area of all vessels at any level of branching. Capillaries have the largest cross-sectional area in the vascular system Recall the relationships that control the resistance across the vessel: predominantly the radius, where a decrease in the radius will increase resistance and vice versa An increase in viscosity will increase vessel resistance Medical Physiology, Chapter 19, 447-460.e1 Blood flow control Intrinsic (Local control) Extrinsic (Hormonal control) So how is local control achieved?  Vasoactive substances in the blood or in the proximity of vascular smooth muscle modulating vasomotor tone of arteries and veins affecting blood pressure and distribution of blood flow  Non-vasoactive substances by acting on the Extracellular fluid volume (ECF) i.e the renin-angiotensinogenII-aldosterone system, arginine vasopressin, atrial natriuretic peptide. Vasoactive Substances VASOCONSTRICTORS Epinephrine (via α 1 receptors) Serotonin Angiotensin II (ANG II) Arginine vasopressin (AVP) Endothelin (ETs) VASODILATORS Epinephrine (via β 2 receptors) Histamine Atrial natriuretic peptide (ANP) Bradykinins Prostaglandin (PGE 2), Prostacyclin ( PGI 2 ) Nitric oxide (NO) Extrinsic Control  Involves response to neural mechanisms and circulating vasoactive substances  Smooth muscle have several types of receptors, including alpha 1 and B2 receptors as learned in the autonomic nervous system  Reminder: at the smooth muscle, alpha 1 causes a vasoconstrictor response, alpha 2 causes a vasoconstrictor response and B2 causes a vasodilator response  Predominantly a sympathetic response, do recall that response depends on receptor density  Parasympathetic innervation of blood vessels is absent with exceptions of genital organs, salivary glands and lower gastrointestinal tract, the mechanism is via stimulating NO release from endothelial cells lining the smooth muscle cell Regulation of Vascular Tone by Endothelial Cells How? The endothelium regulates vascular tone by the following:  Release of vasodilators such as nitric oxide (NO) and prostacyclin  ▪ Release of the vasoconstrictor endothelin  ▪ Conversion of angiotensin I to angiotensin II Netter's Essential Physiology, Chapter 13, 130-150 Regulation of Blood Pressure Involves the regulation of cardiac output and systemic resistance through various mechanisms Arterial baroreceptors Renal juxtaglomerular apparatus Cardiopulmonary baroreceptors MAP= CO X TPR recall that CO = HR x SV More about the regulation of blood pressure in vascular 3 and 4 Four systems regulate blood pressure 1) heart, which supplies the pumping pressure (CO) 2) the blood vessel tone, which largely determines systemic resistance (TPR or SVR) 3) The kidney, which regulates intravascular volume (BV or ECF) 4) hormones or local factors, which modulate the functions of the other three systems Pathophysiology of Heart Disease: An Intr oduction to Cardiovascular Medicine, 7e The figure depicts element ts that will lead to an increase in blood pressure What is Hypertension? Blood pressure (BP) high enough to be a danger to their well-being. Normal Blood Pressure