Lecture #7: Neural Regulation of the Cardiovascular System PDF

Lecture Lecture##7:67:Neural NeuralRegulation Regulationofof The TheCardiovascular CardiovascularSystem System 10/23/23 Fernando Gomez-Pinilla, Ph.D. Fernando Gomez-Pinilla, Ph.D. Dept. Integrative Biology & Physiology Dept. Integrative Biology & Physiology c144/244; F. Gomez-Pinilla; UCLA c144/244...

Lecture Lecture##7:67:Neural NeuralRegulation Regulationofof The TheCardiovascular CardiovascularSystem System 10/23/23 Fernando Gomez-Pinilla, Ph.D. Fernando Gomez-Pinilla, Ph.D. Dept. Integrative Biology & Physiology Dept. Integrative Biology & Physiology c144/244; F. Gomez-Pinilla; UCLA c144/244; F. Gomez-Pinilla; UCLA • Consists of a pump (heart), a fluid (blood), and a series of conduits (blood vessels). • Functions to transport nutrients, oxygen, wastes, and other substances around the body to maintain homeostasis. • The ultimate goal is to deliver energy and O2 to all organs !! c144/244; F. Gomez-Pinilla; UCLA Fluid moves from capillaries to tissue and back to capillaries exchange of O2, CO2, and nutrients occurs at the capillary bed F. Gomez-Pinilla, C144/244; UCLA Main forces affecting distribution of fluids across capillary and tissue Hydrostatic pressure and osmotic pressure of blood determine direction of flux F. Gomez-Pinilla, C144/244; UCLA Tissue perfusion is the result of: • Cardiac output, depends on beating force and cardiac filling pressure (function of venous pressure) • Vascular resistance, diameter of precapillary arterioles • (veins are compliant and offer little resistance) • Pressure: • Normal systolic pressure is 120 mm Hg (ventric. contraction), and diastolic pressure is 80 mm Hg (ventric. filling) • Pressure is lower in venous side (veins can stretch) • Hypertension Vs Hypotension Blood Flow = Perfussion Pressure Vascular Resistance c144/244; F. Gomez-Pinilla; UCLA • Organ perfusion depends on: – Gradient of pressure – Resistance to flow through the tissue bed • Vascular Tone is necessary to maintain blood flow • Failure in vascular tone & perfusion may produce shock syndrome • The ultimate goal is to deliver energy and O2 to all organs !! How does ANS control cardiovascular function? • ANS regulates heart rate, cardiac filling pressure and output, and vascular resistance • Heart innervated by SNS and PNS • Heart rate, contractile force, and output are increased by SNS and decreased by PNS • Blood vessels innervated by SNS, primarily at precapillary arterioles. Veins are also innervated but efficacy is low • Vasoconstriction is most frequent action which depends on relative density of norepinephrine receptor subtypes • Adrenal medulla (via SNS stimulation) secretes catecholamines epinephrine and norepinephrine to blood stream resulting in vasoconstriction c144/244; F. Gomez-Pinilla; UCLA Control of Cardiovascular Function: Integrated response involving neural, endocrine, and behavioral regulation • Many reflexes to adjust to changes in pressure, volume, and redistribution of blood Autonomic Control of the heart • The heart is innervated by the SNS and PNS at the sinoatrial node (pacemaker cells) • Sympathetic nervous systems (SNS) via Norepinephrine causes increases heart rate and pump volume. • • Parasympathetic nervous system (PNS) via Acetylcholine causes decreased heart rate and arterial pressure. Parasympathetic (-) tone dominates during resting, therefore heart rate can accelerate by decreasing PNS tone • Little brain of the heart • https://www.insidescience.org/video/3d-modelhearts-brain • https://www.google.com/search?client=firefoxb-1d&sca_esv=575656203&q=neurons+in+the+hea rt&tbm=vid&source=lnms&sa=X&ved=2ahUK Ewih65jy5YqCAxVjIUQIHRpkDrYQ0pQJegQI CxAB&biw=1411&bih=942&dpr=2#fpstate=ive &vld=cid:6d3bfdb6,vid:LKRTR5oPKJ8,st:0 9 Autonomic Control of the heart in medulla and brainstem • Stellate ganglion cells (SNS; superior cervical ganglion) send postganglionic axons to heart. Vagus nerve (PNS). • Centers in medulla provides basal autonomic drive • Parasympathetic preganglionic neurons in brainstem controlling heart also receive input from respiratory systems -cardiorespiratory integration. • Emotional contribution to ANS via diencephalic and telencephalic connections c144/244; F. Gomez-Pinilla; UCLA Cardiovascular Control Center in Medulla • Tonic vasoconstriction exists during resting via constant SNS activity • Basal vasomotor tone allows modulation of vascular resistance 11 Integration of SNS and PNS pathways controlling heart and blood vessels cVLM Main PNS integrators of vasomotor tone: rostral ventrolateral medulla (rVLM), caudal VLM (cVLM), nucleus tractus solitarius (NTS) PNS: NTS, nucleus ambiguus (NE) c144/244; F. Gomez-Pinilla; UCLA Evidence for centers (rVLM and cVLM) controlling blood pressure Activated by glutamate and inhibited by GABA c144/244; F. Gomez-Pinilla; UCLA baroreceptor reflex controls blood pressure • Negative feedback reflex that maintains arterial pressure within a range • Afferents: Baroreceptors (stretch receptors) in aortic arch and carotid sinus • Baroreceptors signal acute pressure changes and convey information to the NST (afferent pathway) • Efferents: parasympathetic and sympathetic innervation of the heart and vasculature • Increased baroreceptor activity (high blood pressure) increases PNS activity to the heart (and decreases SNS activity to heart and vasculature), restoring pressure c144/244; F. Gomez-Pinilla; UCLA Baroreceptors send pressure information to NST and brain stem to regulate BP (afferent pathway) c144/244; F. Gomez-Pinilla; UCLA Brain stem centers of baroreceptor reflex • • • • • • • Arterial baroreceptors and chemoreceptors use IX n (glossopharyngeal), X (vagus) to reach NST rVLM, cVLM, parabrachial nucleus (PBN) process CV input Other areas: medulla (area postrema, A5 cell group), hypothalamus (PVN, vestibular region of arcuate nucleus) and midbrain (PAG) NST connects with parasympath pregangl in caudal ventrolateral medula (cVLM) -RVLM- sympath pregangl neurons (IML) -heart and vasculature NST also innervates vagal cardiomotor neurons in nucleus ambiguus and dorsal motor nucleus associated with PNS outflow Excitatory (glutamate) and inhibitory (GABA) neurotransmitters are mainly involved in NST Decrease in baroreceptor input (low pressure) stimulates release of vasopressin and adrenal function resulting in release of kidney renin c144/244; F. Gomez-Pinilla; UCLA Baroreceptor reflex circuit c144/244; F. Gomez-Pinilla; UCLA The baroreceptor reflex maintains blood pressure within a physiological range c144/244; F. Gomez-Pinilla; UCLA Arterial baroreceptors can adapt output in response to stretch takes mins takes days c144/244; F. Gomez-Pinilla; UCLA Baroreceptors adapt to prolonged stretch c144/244; F. Gomez-Pinilla; UCLA Neuroendocrine control of the CV system • ++SNS outflow - via adrenal gland releases cathecolamines (E, NE) to blood, acting on sympathetic targets to increase heart rate and to modulate vascular resistance • ++SNS outflow - activation of ß-adrenergic receptors in kidney to release renin into blood Angiotensinogen ---------->angiotensin (vasoconstriction) • Vasopressin is released from posterior pituitary to : Potentiate baroreceptor reflex Promote vasoconstriction via direct action on arterioles Induce antidiuresis acting on kidney (water retention) c144/244; F. Gomez-Pinilla; UCLA Renin-angiotensin system controls blood pressure F. Gomez-Pinilla, C144/244; UCLA Other reflexes facilitate CV homeostasis • Hypoxemia activates chemoreceptors in carotid sinus resulting in vasoconstriction in most tissues -- more blood to brain!! NST and rVLM involved • Posture changes, standing demands vasoconstriction in legs. Vestibular afferents • Exercise increases cardiac output and redistributes blood to sk muscle (sensory feedback) • Behavioral integration, e.g., SNS activation in fight-or-flight response inhibits baroreceptor reflex c144/244; F. Gomez-Pinilla; UCLA Behavioral regulation • Water and salt intake are essential for maintaining blood volume • posture regulation of cardiac output, e.g., lying down increases cardiac filling and cardiac output c144/244; F. Gomez-Pinilla; UCLA The ultimate goal of circulation is to deliver fuels and O2 to all organs !!