Biophysics of Heart and Circulation. Heart as a source of biopotentials.

Heart as a pump. Blood flow in vessels.

Ján Jakuš

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.

Heart - structures

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Heart – Source of Electric Biopotentials

Action Potential of Heart Muscle

Plateau phaseCa2+ influx

Action Potential of Sinoatrial Node, and Prepotential

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

Heart as a Pump

Heart – 2 coupled pumps

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Dynamics of Heart

Heart - 2 pumps, working together at the same timeSystole - ejection of blood from ventricles-H.contractionDiastole- filling the ventricles with blood- H.relaxation

Volume of blood from RV= Volume of blood from LVSystolic 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

DIASTOLE - filling SYSTOLE - ejection

Blood Pressures in Heart

Right Atrium (systole/diastole) = +0,6 /-0,6 (kPa)Right Ventricle = 4,6 / 0 !Pulmonary Artery = 4,6 / 1,2Left Atrium = +0,6 /-0,6Left ventricle = 16 / 0 !Aorta = 16 / 10At 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)

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 vessels enables:

1.Blood flow during diastole,

2.Diastolic BP,

3 Lower Work of Heart

BLOOD CIRCULATIONA./ 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 = 30 mmHg (4 kPa)Portal blood circuit (btw. Hepatic artery and Portal vein)Fetal blood circuit –in foetusB./Distributive circuit (highly pressurized – aorta, arteries)Resistive circuit(arteriolies-contain smooth muscles in wallDiffusive 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

Blood flow Blood flow F ( l.s-1 )=Pressure of 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 . L η - blood viscosity, L- lenght of vessel,• π- Ludolph number,P1,P2- B.Pressures)

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

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 it informs if flow is laminar (when R <, = 1100) η or turbulent ( when R > 1100)

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

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)

Filtration at Capillary Loop

Capillary – is a place for filtration of water and nutritiens and a resorption of metabolic wastes , also

for O2 and CO2diffusion.

Capillary Filtration and Resorption - animation

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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 countries3. 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

Atherosclerosis of Heart Coronary Vessels-a reason for heart stroke

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

„Stenting“ and „By- passing“

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Thank You for Comming and Attention