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Biophysics of Heart and Circulation: Understanding the Mechanics and Physiology of the Heart

This article provides a comprehensive overview of the biophysics of the heart and circulation, covering topics such as the heart as a source of biopotentials, the heart as a pump, blood flow in vessels, and the anatomy of the heart. It also discusses the action potential of the heart muscle, ECG readings, and various aspects of blood circulation.

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Biophysics of Heart and Circulation: Understanding the Mechanics and Physiology of the Heart

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  1. Biophysics of Heart and Circulation. Heart as a source of biopotentials. Heart as a pump. Blood flow in vessels. Ján Jakuš

  2. Anatomy of Heart - consists of 4 chambers: from 2 Atrias (A) and 2 ven-tricles (V) - wall of the Left Ventricle (LV ) is 3 x thicker than a wall of the Right Ventricle (RV) - between RA and RV there is a tricuspid valve, bet-ween LA and LV is a bicuspid valve. - within the pulmonary artery, at a root where it leaves the heart, there is the pulmonary valve. - similarly, within the aorta there is the aortal valve - two coronary arteries bring the nutritiens and O2 for heart muscle - The conductive system (nerve tissue within the heart muscle): Sinoatrial node (SA), Atrio-Ventricular node (AV ), Hiss bundle,Two branches of Tawara, Purkynie fibers.

  3. Heart - structures

  4. Heart – Source of Electric Biopotentials

  5. Action Potential of Heart Muscle Plateau phase Ca2+ influx

  6. Action Potential of Sinoatrial Node, and Prepotential

  7. Spreading of Electric Depolarization in the Heart ECG (see practicals) is a record of heart biopotentials from the body surface. Waves: P,T,U, Swings: Q,R,S, Segments: PQ,ST,QT, Intervals: PQ,ST,QT

  8. Heart as a Pump

  9. Heart – 2 coupled pumps

  10. Dynamics of Heart Heart- 2 pumps, working together at the same time Systole - ejection of blood from ventricles-H.contraction Diastole- filling the ventricles with blood-H.relaxation Volume of blood from RV= Volume of blood from LV Systolic volume (SV)=70 ml ( a volume of blood ejected from each ventricle during heart contraction) Diastolic volume of a ventricle (DV) = 130 ml (this blood volume retained at ventricles during diastole Cardiac Output / min:Co= SV x Heart rate/ min. Co =70 x 72 = 5 (l/min.) Work of heart/60 years of life = move 60.000 kg of steel to the altitude of 8.000 m Work of LV= 0.94 J/systole, Work of RV= 0.19 J/ systole

  11. DIASTOLE - filling SYSTOLE - ejection

  12. Blood Pressures in Heart Right Atrium (systole/diastole) = +0,6 /-0,6 (kPa) Right Ventricle = 4,6 / 0 ! Pulmonary Artery = 4,6 / 1,2 Left Atrium = +0,6 /-0,6 Left ventricle = 16 / 0 ! Aorta = 16 / 10 At diastole, there are 0 pressures within the ventricles ! At diastole, there are positive values of blood pressures, both in the aorta and pulmonary artery, because ELASTICITY of the vessels (See practical –A model of elasticity) 1kPa=7.5 mmHg (torr)= 10 (water cm)

  13. Elasticity of aorta and arteries (because a kind of elastic fibres are in their walls) During the heart systole - blood distends the aorta (kinetic energy -E- of a blood flow changes into a potential E), stored in the walls - we can take Syst.BP Heart diastole- because no blood.diameter of vessels decreases (potential Energy changes into a kinetic one)- diastolic BP is measured Elasticity of vesselsenables: 1.Blood flow during diastole, 2.Diastolic BP, 3 Lower Work of Heart

  14. BLOOD CIRCULATION A./Big blood circuit- between LV and RA ( there is a high BP and Mean Pressure gradient ( PG)is 100 mm Hg (15kPa) Short blood circuit (Lung circuit)-between RV and LA, PG = 30mmHg (4 kPa) Portal blood circuit (btw. Hepatic artery and Portal vein) Fetal blood circuit –in foetus B./Distributive circuit(highly pressurized – aorta, arteries) Resistive circuit(arteriolies-contain smooth muscles in wall Diffusive circuit(capillaries-they create capillary loops) Capacitive circuit(veins and lymphatic vessels) Blood flows only along the Pressure gradient ! Highest flow - in aorta- 30 cm/s, Lowest flow - in cap- illaries - 1mm/s

  15. Blood flow Blood flowF ( l.s-1 )=Pressureof blood/ Resistance of vessel, F ( l.s-1) = P/ R • Blood flow depends linearly on Pressure Gradient, and non-linearly on an arteriolar resistance, as well as on a blood viscosity / and thus on composition of a blood/ • Blood viscosity (is 4.5 x higher (4.5 mPa/s) then visco-sity of distilled water. (e.g. when viscosity increases a blood flow decreases and vice versa. Poiseuille-Hagen Law Q= π . r4 . (P1-P2)(Q- amount of blood, r - vessel radius 8 . η . Lη - blood viscosity, L- lenght of vessel, • π- Ludolph number,P1,P2- B.Pressures)

  16. Bernouli´s Law When blood flows through the narrow vessel the velocity of flow is higher but pressure of blood within is lower (and vice-versa) Fig.30-17

  17. TYPES OF BLOOD FLOWLaminar flow – parabolical shape of a streamline with max. velocity in the middle of the stream and the lowest velocity at the edges. Turbulent flow- velocity is very high in all directions, it creats a soundRaynolds number R = ρ.d.v itinforms if flow is laminar(when R <, = 1100)η or turbulent ( when R > 1100)

  18. Types of Blood Pressures(curve is taken from a direct measurement of BP)

  19. Measurement of BP(non-direct method) Riva Rocci´s auscultation method,Korotkov Sounds, Systolic and diastolic BP are taken (See practical for theory and procedure)N = 90/60 -140/80 (mmHg)

  20. Filtration at Capillary Loop Capillary – is a place forfiltrationof water and nutritiens and a resorption of metabolic wastes , also for O2 and CO2diffusion.

  21. Capillary Filtration and Resorption - animation

  22. Failures of Capillary Filtration and Resorption When the capillary transfer is damaged -the OEDEMA (tissue swelling) appears. It is an accumulation of fluid among cells Reasons: 1.Increase of Systemic Blood Pressure (hypertension), 2. Decrease of an Oncotic Presure- less than - 25 mmHg (a suction effect is lower and water retains within the tissue, that swells- as it appears in a disease Kwashiorkor, which is kind of protein deficiency) ( with typical big bellies in childrens) at economical poor countries 3.Increase in Capillary Permeability(something is wrong with the capillary wall- as seen in the Vibration disease or follo- wing some toxic effect of animal poisons on vessel permea- bility, e.g. snakes or scorpions ) 4. Disorders affecting the Lymphatic System ( the lymphatic circulation stops, because either cancer or parasite blocks the flow of lymph in lymphatic vessels

  23. Atherosclerosis of Heart Coronary Vessels-areason for heart stroke

  24. TREATMENT:. Non-Surgical Angioplasty (Stenting) or Surgical (By-passing)

  25. „Stenting“ and „By- passing“

  26. Thank You for Comming and Attention

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