Neural_Control_of_Cardiovasular_System_2023 (2).pptx
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Neural Control of the Cardiovascu lar System Joseph N. Benoit, Ph.D. Professor of Physiology Source Text • Guyton & Hall Textbook of Medical Physiology, 14th Edition • Chapter 18: Nervous Regulation of the Circulation and Rapid Control of Arterial Pressure • Chapter 20: Cardiac Output, Venous Retu...
Neural Control of the Cardiovascu lar System Joseph N. Benoit, Ph.D. Professor of Physiology Source Text • Guyton & Hall Textbook of Medical Physiology, 14th Edition • Chapter 18: Nervous Regulation of the Circulation and Rapid Control of Arterial Pressure • Chapter 20: Cardiac Output, Venous Return, and Their Regulation Session Objectives • Locate the cardiovascular control center in the brainstem. • Delineate the interconnections of various locations in the brain with the cardiovascular control center. • Identify the various inputs to the cardiovascular control center. • Compare and contrast the Sympathetic and Parasympathetic outputs from the cardiovascular control center. • Describe the need for central cardiovascular control of blood flow given that generally the main control of blood flow to the tissues is by local control. • Describe the importance of tonic vasomotor control in the vasculature. • Relate the baroreceptor function to the cardiovascular control center. • Correlate the regulation of blood pressure to the function of the cardiovascular control center. • Describe the influence of carotid body and aortic arch input to the cardiovascular control center. • Explain intermediate to long-term regulation of the circulation by describing the release, cardiovascular target organs, and mechanisms of cardiovascular effects for angiotensin II, arginine vasopressin, and atrial natriuretic factor. Neural Control of Cardiovascular System is Through the Autonomic Nervous System Sympathetic Nervous System Parasympathetic Nervous System Sympathetic Nervous System • Heart • Increase Heart Rate • Increase Contractility • Blood Vessels • All blood vessels except capillaries are innervated. • SNS Activation Affects • • Afterload primarily via Small Arteries and Arterioles Preload primarily via large vessels, mainly veins. Parasympathetic Nervous System • Heart • Decrease Heart Rate • Decrease Contractility • Blood Vessels • Minor direct role in blood vessel control Vasomotor Center in the Brain • Vasomotor Center Transmits • Parasympathetic Impulses via the vagus verve • Sympathetic Impulses via sympathetic nerves • Important Areas of Vasomotor Center • Vasoconstrictor Area • Vasodilator Area • Sensory Area Concept of Vasomotor Tone • Lateral Portions of Vasomotor Center • Sympathetic Outflow • Transmitter is norepinephrine • Medial Portions of Vasomotor Center • Vagal Outflow • Transmitter is acetylcholine Rapid Control of Arterial Pressure by the Nervous System • Neural Activity Involves Simultaneous Sympathetic Activation and Reciprocal Inhibition of Parasympathetic Vagal Inhibitory Signals • Three major actions explain the increase in arterial pressure • Arterioles are constricted • Increase Total Peripheral Resistance • Increase Arterial Pressure • Venous and large vessel reservoirs are constricted • Increase Preload • Heart is directly stimulated • Increased Heart Rate • Increased Contractility Reflex Mechanisms for Maintaining Normal Arterial Pressure • Baroreceptors • Spray-type nerve endings in arterial wall • Firing rate increases when stretched • Major Locations • Carotid Sinus (Wall of internal carotid arteries, slightly above the carotid bifurcation) • Wall of the aortic arch • Respond Very Rapidly to Changes in Arterial Pressure • Activation of Baroreceptors • Inhibit the Vasoconstrictor Center • Activate the Vagal Parasympathetic Center Baroreceptor Function • Provide moment to moment control of arterial pressure • Attenuate Blood Pressure Changes During Changes in Body Posture Carotid and Aortic Chemoreceptors • Carotid Bodies • Located at bifurcations of the common carotid arteries • Each chemoreceptor receives it’s own blood supply. • Respond to reduced arterial oxygen • Reduced Arterial Pressure lowers blood flow to chemoreceptors which decreases O2 and increases CO2 & H+ • Vasomotor Center is excited, Blood pressure returned towards normal Atrial & Pulmonary Artery Reflexes that Regulate Arterial Pressure • Low-pressure stretch receptors in pulmonary artery and atria. Other Neural Mechanisms of Blood Pressure Control • CNS Ischemic Response • Cushing Reaction • Skeletal Nerves & Muscles • Abdominal Compression Reflex • Respiratory Waves Cardiac Output & Venous Return • Cardiac Output – quantity of blood pumped into the aorta each minute • Factors Affecting C.O. • • • • Level of body metabolism Exercise Age Body size • Cardiac Index is cardiac output per square meter of body surface area. • Venous Return – quantity of blood flowing from the veins into the right atrium each minute. Control of Cardiac Output by Venous Return Venous Return Curve • Relates venous return to Right Atrial Pressure • Mean Circulatory Filling Pressure (Mean Systemic Filling Pressure) Factors Affecting Venous Return Curve The Cardiac Output Venous Return Relationship Whole Body Cardiovascu lar Responses
