Ch.3 Cardiac Physiology Summer 2023/2024 PDF

Physiology (0603302) Ch.3 Cardiac Physiology Summer Semester-2023/2024 Dr. Mohammad A. Abedal-Majed School of Ag...

Physiology (0603302) Ch.3 Cardiac Physiology Summer Semester-2023/2024 Dr. Mohammad A. Abedal-Majed School of Agriculture The University of Jordan STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 1  (327) How does human circulatory system work – 3D animation – in English – YouTube (328) Human Heart Anatomy And Physiology | How Human Heart works? (3D Animation) - YouTube (335) Circulatory System and Pathway of Blood Through the Heart - YouTube STOP SAYING " I WISH" START SAYING "I Dr. Mohamed Abedal-Majed (19-3-2022) 2 WILL"  Blood flow STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 3  Vascular System -pulmonary circulation (short circulation) (low pressure circulation) -delivery of poorly oxygenated blood to the lungs -R ventricle → pulmonary artery → pulmonary vessels -delivery of highly oxygenated blood to the heart -pulmonary vessels → pulmonary vein → L atrium -systemic circulation (high pressure circulation) -delivery of highly oxygenated blood to the tissues -L ventricle → aorta → systemic vessels -delivery of poorly oxygenated blood to the heart -systemic vessels → vena cava → R atrium R ventricle → pulmonary artery → pulmonary vessels → pulmonary vein → L atrium → L ventricle → aorta → systemic vessels → vena cava → R atrium STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 4  Vascular System *Functional components of the circulatory system -pump (heart) -distributing (arterial system) & collecting tubes (venous system) -exchange system (capillary beds) 1) The pumps -right ventricle -propels blood through the lungs (pulmonary circulation) -blood acquires O2 from inspired air -CO2 leaves blood & is expelled via expired air -left ventricle -propels blood through all other tissues (systemic circulation) -delivers O2 & other nutrients to tissues -obtains CO2 & other waste products from tissues STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 5  Vascular System 2)Distributing (arterial system) & collecting tubes (venous system) -arterial system -branching of aorta & pulmonary artery -progressively smaller vessels -arteries → arterioles → capillaries -venous system -empty into vena cava & pulmonary vein -joining of smaller vessels (become progressively larger) -capillaries → venules → veins STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 6  Vascular System 3) exchange system (capillary beds) If cellular metabolism was not changed but the blood flow through a tissue’s capillaries was reduced, how would the venous blood leaving that tissue differ compared to that before flow reduction? STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 7 Cardiac output = Stroke Volume X Heart Rate CO = SV x HR Stroke Volume: volume of blood pumped by each ventricle per beat or stroke (averages 70 ml/beat) Heart Rate: heart beats/min (averages 70 beats/min) CO = SV x HR (cardiac output increases or decreases in CO= 70 ml/beat x 70 beats/min response to changes in heart rate or stroke = 4,900 ml/min ≈ 5 liters/min volume. i.e. when one of them increase it will Resting cardiac output ≈ 5 L/min increase the cardiac out put) During exercise cardiac output can increase to 20 to 25 L/min STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 8 https://www.facebook.com/whalesscience98/videos/408888647029884  Heart valves 1. Atrioventricular valve(from atria to ventricle).: open when atria contract, close when ventricle contract Left: mitral: Right: tricuspid 2. Semilunar valve(from ventricles to the aorta and pulmonary artery).: open when ventricles contract, close when ventricles relaxed. Left: aortic valve Right: pulmonic valve STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 9  Electrical Activity of Cardiac Muscle Cells Specialized muscle cells in the SA node “spontaneously” depolarize resulting in the generation of an action potential Due to electrical coupling of cells via gap junctions, the action potential is propagated to all other cells in the heart Pacemaker cells depolarize without neural stimulation and set the basal heart rate Motor neurons from the Sympathetic and Parasympathetic NS modify the basal rate of pacemaker depolarization Dr. Mohamed Abedal-Majed (19-3-2022) 10 STOP SAYING " I WISH" START SAYING "I WILL" *Cardiac AP propagation Cardiac Action Potentials 1-AP spontaneously generates in the SA node 2-AP rapidly propagates cell-to-cell across the atrial myocytes → both the L & R atria contract 3-AP slowly propagates cell-to-cell through the AV node & bundle of His -AV node = specialized region for conduction of APs between the atria & ventricles -bundle of His = transmits APs from the AV node through the interventricular septum -creates delay between atrial & ventricular contractions This delay allows time for the atria to finish contraction and empty their contents into the ventricles before ventricles start to contract. 4-AP rapidly propagates cell-to-cell through the bundle branches -transmits APs to the L & R ventricles 5-AP rapidly propagates cell-to-cell through the Purkinje fibers -transmits APs to the inner portions of the L & R ventricles 6-AP rapidly propagates cell-to-cell through ventricular myocytes -both the L & R ventricles contract -rapid conduction through the BBs, Purkinje fibers, & myocytes → nearly synchronous contraction of all ventricular myocytes STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 11  Cardiac Action Potentials *Specialized conduction system of the heart -SA node, AV node, bundle of His, bundle branches, & Purkinje fibers -all are specialized cardiac myocytes (not neurons) -responsible for ensuring each heart beat follows specific sequence 1-both atria contract, almost simultaneously 2-brief pause (slow propagation through AV node) 3-both ventricles contract, almost simultaneously 4-heart relaxes & refills 0.1 sec 0.5 sec STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 0.3 sec12  Cardiac Action Potentials *Cardiac action potentials are relatively long -skeletal AP = 1-2 msec -APs are driven by voltage-gated Na+ & K+ channels -only localized voltage-gated Ca2+ channels (do not contribute to APs) -cardiac AP = 100-250 msec -APs are driven by voltage-gated Na+, K+, & Ca2+ channels -voltage-gated Ca2+ channels are especially important for prolonging APs STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 13  Cardiac Action Potentials *Resting membrane potential (phase 4) -membrane is more permeable to K+ than either Na+ or Ca2+ -K+ leak channels -open at resting membrane potential -resting membrane potential is ≈ the equilibrium potential for K+ -concentration gradient drives K+ movement out of cells -electrical gradient drives K+ movement into cells -voltage-gated channels (Na+, Ca2+, K+) are closed EK+ = -94 mV ENa+ = +71 mV ECa2+ = +132 mV STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 14  Cardiac Action Potentials *Depolarization (phase 0) (Spontaneous depolarization) -voltage-gated Na+ channels open (funny Na+ channels are open ) -stimulated by attainment of threshold potential -steep ↑ in membrane permeability to Na+ drives depolarization (↑↑ intracellular cations) -concentration gradient drives net movement into cell -electrical gradient also drives movement into cell (when Vm is negative) -K+ leak channels become blocked during depolarization -mechanism unknown -↓ in membrane permeability to K+ STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 15  Cardiac Action Potentials *Initial repolarization (phase 1) -voltage-gated Na+ channels inactivate -occurs spontaneously, briefly after opening (time, not voltage-dependent) -steep ↓ in membrane permeability to Na+ -voltage-gated K+ channels open -stimulated by attainment of threshold potential (open slower than Na+ channels) - ↑ in membrane permeability to K+ drives repolarization (↓ intracellular cations) -concentration gradient drives net movement out of cell -electrical gradient also drives movement out of cell (when Vm is positive) STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 16  Cardiac Action Potentials *Repolarization plateau (phase 2) (slow response action potential) -voltage-gated K+ channels remain open -concentration gradient drives net movement out of cell -electrical gradient also drives movement out of cell (when Vm is positive) -voltage-gated Ca2+ channels open -stimulated by attainment of threshold potential (open slower than Na+ & K+ channels) -↑ in membrane permeability to Ca2+ opposes repolarization driven by K+ efflux -concentration gradient drives net movement into cell -electrical gradient also drives movement out cell (when Vm is positive) then movement into cell (when Vm is negative) -net cation efflux via K+ ≈ net cation influx via Ca2+ STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 17  Cardiac Action Potentials *Final repolarization (phase 3) -voltage-gated K+ channels remain open -concentration gradient drives net movement out of cell -voltage-gated Ca2+ channels inactivate -occurs spontaneously, briefly after opening (time, not voltage-dependent; inactivate slower than Na+ channels) -↓ in membrane permeability to Ca2+ allows K+ efflux to drive repolarization again -blockage of K+ leak channels is removed -exact timing unknown -further ↑ in membrane permeability to K+ -concentration gradient drives net movement out of cell STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 18  Cardiac Action Potentials *Resting membrane potential (phase 4) -voltage-gated Na+, K+, & Ca2+ channels close -stimulated as membrane approaches resting potential -return to resting membrane permeabilities & concentrations STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 19  Cardiac Action Potentials *Fast response action potential -rapid depolarization phase STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 20  Cardiac Muscle Contraction *Cardiac cycle A-contraction of cardiac muscle → ↑ ventricular chamber pressure → closing of AV (inlet) valves → opening of SL (outlet) valves B -relaxation of cardiac muscle → ↓ ventricular chamber pressure → closing of SL (outlet) valves → opening of AV (inlet) valves -closing of AV valves → end of diastole, beginning of systole -closing of semilunar valves → end of systole, beginning of diastole STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 21  Cardiac Muscle Contraction *Cardiac cycle S1 = first heart sound (closing of the AV valve) 1-diastole S2 = second heart sound (closing of the aortic valve) -left ventricular (LV) pressure is low -specifically, lower than left atrial pressure -AV valve opens into the LV 2-atrium depolarizes (P wave) & then contracts -helps complete ventricular filling -minimal change in LV pressure 3-ventricle depolarizes (QRS complex) & then contracts -AV valve closes (S1) but aortic valve yet to open -left atrial pressure < LV pressure < aortic pressure -results in isovolumetric contraction -steep ↑ in ventricular pressure STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 22  Cardiac Muscle Contraction 4-ventricular pressure surpasses aortic pressure -aortic valve opens & blood is ejected into the aorta -↑ aortic pressure 5-ventricle repolarizes (T wave) & then relaxes -aortic valve closes (S2) but AV valve yet to open -left atrial pressure < LV pressure < aortic pressure -results in isovolumic relaxation -steep ↓ in ventricular pressure 6-atrial pressure (not shown) surpasses ventricular pressure -AV valve opens & blood flows into the ventricle STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 23  Cardiac Muscle Contraction STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 24  Blood Pressures *Circulation is pressure-driven flow of blood in order to transport O2, CO2, nutrients, hormones, etc.. throughout the body (blood flow) These two pressure types are additive when the vessel is located below the heart (P + gh) where h = height difference, g = gravitational effect, and r = density of the fluid These two pressures are subtractive when the vessel is located above the heart (↓ pressure in vessels above heart) Pressure produced by the heart must be sufficient for blood to reach the brain (↑ pressure in vessels below heart) STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 25  Blood Pressures Blood pressure varies between a maximum (systolic) and a minimum (diastolic) pressure Systolic pressure: The maximum pressure exerted in the arteries when the blood is ejected into them during ventricular systole  averages 120 mmHg Diastolic pressure: The minimum pressure within the arteries occurs when the blood is draining off into the rest of vessels during ventricular diastole  averages 80 mmHg Pulse pressure: is the difference between systolic and diastolic pressure (systolic – diastolic) Blood pressure = 120/80 Pulse pressure  40 mmHg Mean arterial pressure: is the average pressure responsible for driving blood forward (average pressure in an artery) -between systolic & diastolic pressures but not midway MAP= diastolic pressure + 1/3 pulse pressure = 80 + (1/3 * 40) = 93 mmHg -systemic circulation = high-pressure, high-resistance circulation -pulmonary circulation = low-pressure, low-resistance circulation Dr. Mohamed Abedal-Majed (19-3-2022) 26 STOP SAYING " I WISH" START SAYING "I WILL"  Blood Pressures -branching of vessels -↑ branching → ↓ vessel diameter -total surface area: capillaries > arterioles > arteries > aorta OR capillaries > venules > veins > vena cava -↑ surface area → ↑ efficiency of diffusion vascular resistance = perfusion pressure/flow resistance of a tube (R) = 8hl/pr4 radius has the largest impact on resistance = h=viscosity, l = length, r = radius -if radius of 1 tube is twice that of a second tube → resistance is 16-times greater in the smaller tube→ flow is 16-times greater in the larger tube -↑ surface area → ↓ blood flow velocity ( slower velocity aids diffusion) Total Cross Mean Blood Inside Diameter Velocity of Blood Vessel Number Sectional Area Length (cm) Pressure (mm) Flow (cm/sec) (cm2) (mm Hg) Aorta 1 20.0 3.1 40.0 13.0 98 Small arteries 45,000 0.14 6.9 1.5 6.0 90 Arterioles 20,000,000 0.030 140.0 0.2 0.3 60 Capillaries 1,700,000,000 0.008 830.0 0.05 0.05 18 Venules 130,000,000 0.020 420.0 0.1 0.1 12 Small veins 73,000 0.27 42.0 1.5 1.0 6 Venae cavae 2 24.0 9.0 34.0 4.5 3 27 STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022)  Blood Pressures Dr. Mohamed Abedal-Majed (19-3-2022) 28 STOP SAYING " I WISH" START SAYING "I WILL"  Resistance &Blood Pressures Resistance =opposition to blood flow in a vascular bed -arterioles have the highest resistance so blood pressure is greatly reduced -capillaries & venules have intermediate resistance -large veins & the vena cava have very low resistance -resistance is related to compliance = (change in volume)/(change in transmural pressure) = ability to distend when pressure or volume is added -compliant vessels readily distend -veins are ~ 20 times more compliant than arteries -storage site of blood volume -arteries are tough vessels with low compliance -storage site of blood pressure -can accommodate large pressures needed to drive flow Dr. Mohamed Abedal-Majed (19-3-2022) 29 STOP SAYING " I WISH" START SAYING "I WILL"  Total peripheral resistance & Blood Pressures *Total peripheral resistance -TPR = (aortic pressure – vena cava pressure)/cardiac output -since vena cava pressure is so low, it is often ignored -TPR ≈ aortic pressure/cardiac output -aortic pressure ≈ TPR * CO -if TPR ↑, aortic pressure &/or CO must also ↑ -the greatest contributors to the TPR are arterioles -(highest resistance) -MAP ≈ TPR * CO STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 30  Total peripheral resistance & Blood Pressures *Total peripheral resistance -flow = (change in pressure)/resistance -flow = (mean arterial pressure – mean venous pressure)/resistance -each organ receives aortic blood flow -each organ is drained by vena cava -therefore, vascular resistance is what determines blood flow through each organ -arteriolar diameter is what determines vascular resistance in each organ STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 31  Total peripheral resistance & Blood Pressures Predict how the blood flow to these various areas might change in a resting person just after eating a large meal. Assuming the reservoir is refilled at a constant rate, how would the flows shown in (b) be different if tube 2 remained the same as it was in condition (a)? STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 32  Clinical Applications *Blood viscosity -anemia (“no blood”) = abnormally low RBC # -blood is less viscous → ↓ TPR → ↓ MAP -polycythemia (“many cells in blood”) = abnormally elevated RBC # -blood is more viscous → ↑ TPR → ↑ MAP *Blood pressure measurement -Heart sounds (lub-dup) are associated with closing of heart valves – First sound occurs as AV valves close and signifies beginning of systole (contraction) – Second sound occurs when Semilunar valves close at the beginning of ventricular diastole (relaxation) 33 STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022)  Blood Pressure Regulation A- Sympathetic nervous system -norepinephrine (NE) (neurotransmitter) is released from sympathetic neurons -circulating catecholamines (NE & epinephrine) are released from the adrenal medulla -bind adrenergic receptors on cardiac muscle cells -beta1-adrenergic receptors = Gs-linked GPCRs -bind adrenergic receptors on vascular smooth muscle cells -beta2-adrenergic receptors = Gs-linked GPCRs -alpha1-adrenergic receptors = Gq-linked GPCRs -alpha2-adrenergic receptors = Gi-linked GPCRs B- Parasympathetic nervous system -acetylcholine (ACh) released from parasympathetic neurons -binds muscarinic ACh receptors on cardiac muscle cells -M2 receptors = Gi-linked GPCRs -bind muscarinic ACh receptors on endothelial cells -M3 receptors = Gq-linked GPCRs 34 STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022)  Regulation of Blood Pressure Summary STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 35  Regulation of Blood Pressure Summary The heart is innervated by both divisions of the autonomic nervous system (sympathetic & parasympathetic), which can modify the rate & strength of contraction. (not initiation of contraction) STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 36  Regulation of Blood Pressure Summary STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 37  Baroreceptor & Volume Reflexes A- Baroreceptor reflex -mechanoreceptors are embedded in the walls of the aortic arch & carotid sinus - baroreceptors (sense changes in vessel stretch/distention) -blood pressure is the force that distends vessels -afferent signals are sent to the CNS -CNS then inhibits sympathetic efferent signaling -CNS then stimulates parasympathetic efferent signaling -alterations in autonomic signaling impacts blood pressure -helps minimize increases or decreases in blood pressure -does not reverse changes in blood pressure -example: -loss of blood that would ↓ blood pressure by 40-50 mm Hg -barorecepetor reflex limits ↓ in pressure to only 10-15 mm Hg -rapid (≤ 1 sec) mechanism to regulate blood pressure -adapts to long-term changes in blood pressure (e.g. hypertension) -will then regulate blood pressure around the new “normal” 38 STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022)  Baroreceptor & Volume Reflexes A- Baroreceptor reflex CNS then inhibits sympathetic efferent signaling -CNS then stimulates parasympathetic efferent signaling Dr. Mohamed Abedal-Majed (19-3-2022) 40 STOP SAYING " I WISH" START SAYING "I WILL"  Baroreceptor & Volume Reflexes A- Baroreceptor reflex -CNS recognizes changes in AP frequency received from baroreceptors -↓ AP frequency (occurs with reduced blood pressure) → ↓ inhibition of sympathetic activity → ↑ HR & SV → ↑ CO → ↑ MAP → ↑ arteriolar vasoconstriction → ↑ TPR → ↑ MAP → ↓ stimulation of parasympathetic activity → ↑ HR & SV → ↑ CO → ↑ MAP STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 41  Baroreceptor & Volume Reflexes A- Baroreceptor reflex -CNS recognizes changes in AP frequency received from barorecpetors -↑ AP frequency (increased blood pressure) → ↑ inhibition of sympathetic activity → ↓ HR & SV → ↓ CO → ↓ MAP → ↓ arteriolar vasoconstriction → ↓ TPR → ↓ MAP → ↑ stimulation of parasympathetic activity → ↓ HR & SV → ↓ CO → ↓ MAP STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 42  Baroreceptor & Volume Reflexes A- Baroreceptor reflex -unable to restore normal blood pressure values -minimizes increases or decreases away from normal but will still be abnormal (in direction of initial problem) -example: MAP is low due to ↓ SV -baroreceptor reflex will stimulate an ↑ in SV, HR, & TPR which will ↑ MAP -HR & TPR were normal initially and they will now be elevated -MAP & SV will ↑ but will still be below normal levels STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 43  Baroreceptor & Volume Reflexes B-Atrial volume receptor reflex -mechanoreceptors embedded in the walls of the atria -atrial volume receptors -directly sense changes in atrial stretch/distention -blood volume is the force that distends the atria -indirectly sense changes in overall blood volume in the circulation -afferent signals are sent to the CNS -CNS then inhibits sympathetic efferent signaling -CNS then stimulates parasympathetic efferent signaling -alteration in autonomic signaling impacts blood pressure -↑ blood volume → ↑ MAP → AVRR → ↓ MAP -↓ blood volume → ↓ MAP → AVRR → ↑ MAP -CNS also stimulates ↑ thirst & ↓ renal Na+/H2O excretion -ability to restore blood volume back to normal values STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 44  Baroreceptor & Volume Reflexes B-Atrial volume receptor reflex -regulation of blood pressure -CNS recognizes changes in AP frequency received from atrial volume receptors -↓ AP frequency (reduced blood volume) → ↓ inhibition of sympathetic activity → ↑ HR & SV → ↑ CO → ↑ MAP → ↑ arteriolar vasoconstriction → ↑ TPR → ↑ MAP → ↓ stimulation of parasympathetic activity → ↑ HR & SV → ↑ CO → ↑ MAP STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 45  Baroreceptor & Volume Reflexes B-Atrial volume receptor reflex -regulation of blood volume -CNS signals to hypothalamus -↓ blood volume → ↓ AVR AP frequency → ↑ thirst -↑ blood volume → ↑ AVR AP frequency → ↓ thirst Antidiuretic hormone (ADH) or Vasopressin STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 46  Baroreceptor & Volume Reflexes B-Atrial volume receptor reflex -regulation of blood volume -CNS signals to hypothalamus & posterior pituitary -↓ blood volume → ↓ AVR AP frequency → ↑ vasopressin production & release → ↓ renal excretion of H2O -↑ blood volume → ↑ AVR AP frequency → ↓ vasopressin production & release → ↑ renal excretion of H2O STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 47  Baroreceptor & Volume Reflexes B-Atrial volume receptor reflex -regulation of blood volume renin–angiotensin–aldosterone system (RAAS) -CNS signals to kidneys -↓ blood volume → ↓ AVR AP frequency → ↑ renin release & RAAS activation → ↓ renal excretion of Na+/H2O -↑ blood volume → ↑ AVR AP frequency → ↓ renin release & RAAS activation → ↑ renal excretion of Na+/H2O STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 48  Blood pressure & RASS STOP SAYING " I WISH" START SAYING "I Dr. Mohamed Abedal-Majed (19-3-2022) 50 WILL"  Clinical Applications *Electrocardiogram (ECG) -graphical tracing of the variations in cardiac electrical potentials as detected at the body surface -sum of all action potentials within the atria & ventricles To provide standard comparisons, ECG records routinely consist of 12 conventional electrode systems, or leads. When an electrocardiograph machine is connected between recording electrodes at two points on the body, the specific arrangement of each pair of connections is called a lead. The 12 leads each record electrical activity in the heart from different locations—six different electrical arrangements from the limbs and six chest leads at various sites around the heart. To provide a common basis for comparison and for recognizing deviations from normal, the same 12 leads are routinely used in all ECG recordings STOP SAYING " I WISH" START SAYING "I WILL" Dr. Mohamed Abedal-Majed (19-3-2022) 51