Blood Pressure Regulation Lecture 13 PDF

Body Systems The Cardiovascular System BIOL10811 Lecture 13: Blood Pressure Regulation Dr Nick Stafford Division of Diabetes, Endocrinology & Gastroenterology School of Medical Sciences Faculty of Biology, Medicine and Health [email protected] November 2024  Ob...

Body Systems The Cardiovascular System BIOL10811 Lecture 13: Blood Pressure Regulation Dr Nick Stafford Division of Diabetes, Endocrinology & Gastroenterology School of Medical Sciences Faculty of Biology, Medicine and Health [email protected] November 2024  Objectives A successful student should be able to Describe the determinants of blood pressure Describe the principals of blood pressure regulation and its integrated control Describe the principals of local autoregulation of blood flow and central regulation of blood pressure Describe the central mechanisms involved in the short- and long-term regulation of blood pressure  Content 1) Introduction to Blood Pressure Regulation 2) Intrinsic Control/Autoregulation of Blood Flow 3) Short Term Regulation of Blood Pressure Baroreceptors Chemoreceptors 4) Long Term Regulation of Blood Pressure Regulation of Blood Volume Regulation of Vascular Tone 5) Special Considerations for Local Flow Pulmonary Circulation Coronary Circulation Cerebral Circulation What is blood pressure and why do we need it?  1) Introduction to Blood Pressure Regulation What is blood pressure and why do we need it? Blood Pressure 11 The force exerted upon vessel re ctu walls as blood flows through Le A minimum pressure (capillary hydrostatic pressure) is required to exchange substances/fluids across 14 capillary networks re ctu Capillary Exchange Le  Determinants of Blood Pressure Total Peripheral Blood Pressure = Cardiac Output X Resistance Force exerted upon Dependent upon HR X SV 12 ure vessel walls as blood arteriolar radius ct Le flows through Autoregulation of local flow Short Term Central Long Term Regulation Regulation Neural Endocrine  Content 1) Introduction to Blood Pressure Regulation 2) Intrinsic Control/Autoregulation of Blood Flow  2) Intrinsic Control/Autoregulation of Blood Flow When local blood flow in a tissue is too low… Active Inactive Tissue Tissue Vasodilatory Metabolites NO K+ CO2 H+ lactate  If blood pressure and flow is still too low to meet demands… Autoregulation insufficient to restore homeostasis... central mechanisms are activated to increase systemic BP  Content 1) Introduction to Blood Pressure Regulation 2) Intrinsic Control/Autoregulation of Blood Flow 3) Short Term Regulation of Blood Pressure Baroreceptors Chemoreceptors  3) Short Term Regulation of Blood Pressure When blood pressure in tissues is still too low… Autoregulation insufficient to restore homeostasis Which branch of the ANS could be activated to return to homeostasis if BP is too low?  3) Short Term Regulation of Blood Pressure When blood pressure in tissues is still too low… Autoregulation insufficient to restore homeostasis HR & SV vasoconstriction Q Which branch of the autonomic nervous system could be activated to restore BP? Sympathetic Parasympathetic  3) Short Term Regulation of Blood Pressure When blood pressure in tissues is still too low… Short term increase Activation of in BP via SNS cardiovascular centres in CNS Detected by activation receptors sensitive increasing CO and to vasoconstriction pressure/chemical changes Autoregulation insufficient to restore homeostasis  3) Short Term Regulation of Blood Pressure When blood pressure in tissues is still too low… Short term increase Activation of in BP via SNS cardiovascular centres in CNS Detected by activation receptors sensitive increasing CO and to vasoconstriction pressure/chemical changes Autoregulation insufficient to restore homeostasis 12 re tuc Le  Baroreceptor Reflexes Response enhanced by Adrenaline/NA secretion from adrenal glands Cardioacceleratory Carotid Centre Activation Sinus HR & CO (Cerebral Fall in Baroreceptor Cardioinhibitory blood flow) BP Inhibition Centre Inhibition Vasomotor Centre Baroreceptors Aortic Vasoconstriction Sinus Activation PNS Cardiovascular Centre in Medulla Oblongata SNS Cardioacceleratory Centre Inhibition HR & CO Rise in Baroreceptor Cardioinhibitory BP Stimulation Centre Activation Vasomotor Centre Vasodilation Inhibition  Chemoreceptor Reflexes Respiratory Rate HR & CO Chemoreceptors Cardioacceleratory Cardioinhibitory Centre Activation Centre Inhibition Respiratory Centre Fall in Activation Fall in Carotid pH Body O2 (Blood) Rise in Medulla Rise in CO2 Oblongata CO2 (CSF) Vasomotor Centre Vasodilation of Activation cerebral vessels Peripheral Blood flow to Vasoconstriction brain Coordination of cardiovascular & respiratory response  When blood pressure in tissues is STILL too low… Short term increase Activation of in BP via SNS cardiovascular activation centres in CNS Detected by increasing CO and receptors sensitive vasoconstriction to pressure/chemical changes Reflex responses insufficient to restore homeostasis Autoregulation insufficient to restore homeostasis Long term increase in BP via increasing Stimulation of blood volume and Endocrine vasoconstriction Response  Content 1) Introduction to Blood Pressure Regulation 2) Intrinsic Control/Autoregulation of Blood Flow 3) Short Term Regulation of Blood Pressure Baroreceptors Chemoreceptors 4) Long Term Regulation of Blood Pressure Regulation of Blood Volume Regulation of Vascular Tone Which organs and glands contribute to long term regulation of BP?  4) Long Term Regulation of Blood Pressure When blood pressure in tissues remains too low… Anti-Diuretic Hormone (ADH/vasopressin) Erythropoietin (Epo) Fall in blood Fall in BP volume or O2 Vasoconstriction Vasoconstriction Endocrine Pituitary Gland response Epo ADH to low BP RBC Fluid Retention formation Blood Thirst volume Renin-Angiotensin-Aldosterone System (RAAS) Lungs Fall in Adrenals renal BP Angiotensin Converting Kidney Renin Enzyme Angiotensinogen Angiotensin I Angiotensin II Aldosterone Vasoconstriction Na+ Reabsorption Liver Fluid Retention  4) Long Term Regulation of Blood Pressure When blood pressure is too high…. Right Atrium Rise in Stretching of Release of cardiac muscle BP & natriuretic peptides cells in right atrium volume and ventricle ANP & BNP Increased Na+ loss Renal in urine Effects Blood Increased water volume loss in urine Reduced thirst Inhibition of ADH, aldosterone, NA & Blood adrenaline release pressure Peripheral Vascular vasodilation Effects Integrated Response to Regulation of Blood Pressure Short term increase Activation of in BP via SNS cardiovascular activation centres in CNS Detected by increasing CO and receptors sensitive vasoconstriction to pressure/chemical changes Autoregulation insufficient to restore homeostasis Long term increase in BP via increasing Stimulation of blood volume and Endocrine vasoconstriction Response Which mechanisms would be activated following severe haemorrhage? Response to severe haemorrhage  Content 1) Introduction to Blood Pressure Regulation 2) Intrinsic Control/Autoregulation of Blood Flow 3) Short Term Regulation of Blood Pressure Baroreceptors Chemoreceptors 4) Long Term Regulation of Blood Pressure Regulation of Blood Volume Regulation of Vascular Tone 5) Special Considerations for Local Flow Pulmonary Circulation Coronary Circulation Cerebral Circulation  5) Special Considerations for Local Flow Blood flow regulation is different in some organs… Pulmonary Circulation Coronary Circulation In lungs arterioles constrict in SNS activity leads to coronary artery vasodilation due regions of low O2 to shunt to predominance of β2-adrenergic receptors blood flow to O2-rich areas In other organs vessels dilate when O2 falls 14 re ctu Le Cerebral Circulation Blood flow to the brain must be preserved at all times In emergencies there is vasodilation of cerebral vessels while there is vasoconstriction in the periphery  Objectives A successful student should be able to  Describe the determinants of blood pressure  Describe the principals of blood pressure regulation and its integrated control  Describe the principals of local autoregulation of blood flow and central regulation of blood pressure  Describe the central mechanisms involved in the short- and long-term regulation of blood pressure