Cardiovascular System Week 9 Dr. Walid Daoud A. Professor.

CardiovascularCardiovascular SystemSystem

Week 9Week 9

Dr. Walid DaoudDr. Walid DaoudA. ProfessorA. Professor

Cardiovascular SystemCardiovascular System________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

FunctionsFunctions::

11--Supplies OSupplies O22, hormones & nutrients to cells, hormones & nutrients to cells..

22--Collects COCollects CO22 and waste products of tissues and waste products of tissues..

33--Thermoregulatory functionThermoregulatory function..

44--Allows blood to pass in a forward directionAllows blood to pass in a forward direction..

Cardiovascular SystemCardiovascular System________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Anatomy of the HeartAnatomy of the Heart::

It pumps blood distributes it allover the body It pumps blood distributes it allover the body according to pressure gradientaccording to pressure gradient..

It is a muscular pump that contracts and It is a muscular pump that contracts and relaxes continuouslyrelaxes continuously..

It is of the size of the fist of the handIt is of the size of the fist of the hand..

It is located in and protected by the thoracic It is located in and protected by the thoracic bony cagebony cage..

Cardiovascular SystemCardiovascular System__________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

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Right side of the heartRight side of the heart::Right atrium, right ventricle and a tricuspid Right atrium, right ventricle and a tricuspid valve in betweenvalve in between..

. .Contains venous blood (70% oxygenated)Contains venous blood (70% oxygenated).. . .Receives blood from superior and inferior Receives blood from superior and inferior

vena cavae that open into the right atrium vena cavae that open into the right atrium (venous return)(venous return)..

In between right ventricle and pulmonary In between right ventricle and pulmonary artery there is a pulmonary valveartery there is a pulmonary valve..


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Left side of the heartLeft side of the heart::

Left atrium, left ventricle with a mitral valve in Left atrium, left ventricle with a mitral valve in betweenbetween..

. .Left atrium receives arterial oxygenated Left atrium receives arterial oxygenated blood from the lungs via 4 pulmonary veins blood from the lungs via 4 pulmonary veins . .

. .In between the left ventricle and aorta there is In between the left ventricle and aorta there is an aortic valve an aortic valve..


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PericardiumPericardium::

A membranous double layer sac formed of inner A membranous double layer sac formed of inner visceral and outer parietal layers with a thin film visceral and outer parietal layers with a thin film of fluid (30 cc)in between them to avoid frictionof fluid (30 cc)in between them to avoid friction..

Cardiac muscleCardiac muscle::

Striated muscle formed of many sarcomeres (dark Striated muscle formed of many sarcomeres (dark and light bands) and rich in mitochondriaand light bands) and rich in mitochondria..

Muscle fibers have no protoplasmic continuity but Muscle fibers have no protoplasmic continuity but there are intercalated discs so the heart is a there are intercalated discs so the heart is a functional syncytium (one unit) i,e. contracts functional syncytium (one unit) i,e. contracts instantaneouslyinstantaneously..

Properties of Cardiac MuscleProperties of Cardiac Muscle________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

11 - -ContractilityContractility..

22 - -RhythmicityRhythmicity..

33 - -ExcitabilityExcitability..

44 - -ConductivityConductivity..

ContractilityContractility________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

It is the ability of cardiac muscle to contractIt is the ability of cardiac muscle to contract

day and night. It obeys 2 lawsday and night. It obeys 2 laws::

11--All or non law:All or non law: either contract to threshold either contract to threshold stimulus or not contract at all to stimulus or not contract at all to

subthreshold stimulussubthreshold stimulus . .

22--Frank Starling law (length-tension relationship)Frank Starling law (length-tension relationship)

↑ ↑ in end-diastolic volume causes ↑ in fiber in end-diastolic volume causes ↑ in fiber length, which causes ↑ in developed tension length, which causes ↑ in developed tension with powerful contractility within limitwith powerful contractility within limit..

ContractilityContractility________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Factors ↑ ContractilityFactors ↑ Contractility::--Increased heart rate e.g., exerciseIncreased heart rate e.g., exercise..

--Sympathetic stimulation via B receptorsSympathetic stimulation via B receptors..--Drugs e.g., digitalisDrugs e.g., digitalis..

--Frank Starling lawFrank Starling law..Factors ↓ ContractilityFactors ↓ Contractility::

--Parasympathetic (vagus nerve) stimulation Parasympathetic (vagus nerve) stimulation (atrial not ventricular muscle)(atrial not ventricular muscle)..

--Bleeding and decrease venous returnBleeding and decrease venous return..--Heart failureHeart failure..

ExcitabilityExcitability________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

It is the ability of the heart to initiate an action It is the ability of the heart to initiate an action potential in response to own depolarizing currentpotential in response to own depolarizing current..

The heart is regular all the time with phases of The heart is regular all the time with phases of refractory periods of excitabilityrefractory periods of excitability::

11--Absolute refractory periodAbsolute refractory period::

Cardiac muscle does not respond to any stimulus Cardiac muscle does not respond to any stimulus whatever its intensity whatever its intensity . .

22--Relative refractory periodRelative refractory period::

Cardiac muscle can respond to action potential due Cardiac muscle can respond to action potential due to strong stimulus and leads to extrasystole to strong stimulus and leads to extrasystole . .


ExtrasystoleExtrasystole::

This result from ectopic focus in the cardiac This result from ectopic focus in the cardiac muscle that competes with SAN (topic focus)muscle that competes with SAN (topic focus)

11--Atrial ectopic focusAtrial ectopic focus..

22--A-V nodal focusA-V nodal focus..

33--Ventricular ectopic focusVentricular ectopic focus..

Causes of ectopic fociCauses of ectopic foci::

Smoking, caffeine, myocadial ischemia or Smoking, caffeine, myocadial ischemia or infarction, mitral stenosis & hyperthyroidisminfarction, mitral stenosis & hyperthyroidism..


Cardiac action potentialsCardiac action potentials::

Threshold stimulus causes depolarizationThreshold stimulus causes depolarization::

Phase 0:Phase 0: Upstroke of action potential (Na Upstroke of action potential (Na+ + influx)influx)..

Phase 1:Phase 1: initial repolarization (K initial repolarization (K++ efflux) efflux)..

Phase 2:Phase 2: plateau (Ca plateau (Ca++++ influx and Na influx and Na++ influx) influx)..

Phase 3:Phase 3: repolarization (K repolarization (K++ efflux) efflux)..

Phase 4:Phase 4: resting membrane potential resting membrane potential..

ConductivityConductivity________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

It is the ability of cardiac muscle to spread excitatory It is the ability of cardiac muscle to spread excitatory impulses in the heart tissue via a specialized impulses in the heart tissue via a specialized conductive system in the cardiac muscleconductive system in the cardiac muscle::

11--Sino-atrial node (SA node)Sino-atrial node (SA node)

It is the pace maker of heartIt is the pace maker of heart..

22--A-V nodeA-V node..

33--Bundle of HissBundle of Hiss..

44--Right and left bundle branchesRight and left bundle branches..

55--Purkinje fibersPurkinje fibers..

Spread of Cardiac ExcitationSpread of Cardiac Excitation________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Depolarization is initiated in SAN, impulses Depolarization is initiated in SAN, impulses spread in atria and converge on A-V node spread in atria and converge on A-V node where impulse is delayed in it to avoid where impulse is delayed in it to avoid irregularity of impulses coming from atria. irregularity of impulses coming from atria. Then wave of depolarization spread from Then wave of depolarization spread from cardiac septum rapidly to Purkinje sustem to cardiac septum rapidly to Purkinje sustem to all parts of ventriclesall parts of ventricles..

Sympathetic stimulation ↑ cardiac conductivity Sympathetic stimulation ↑ cardiac conductivity while vagal stimulation lengthened and slow while vagal stimulation lengthened and slow

conductivity in SAN, AVN & atrial fibersconductivity in SAN, AVN & atrial fibers . .

RhythmicityRhythmicity________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

It is the ability of cardiac muscle to initiate an It is the ability of cardiac muscle to initiate an action potential of its own regularly. action potential of its own regularly. Normally SAN has the highest rhythmicity, Normally SAN has the highest rhythmicity, therefore the SAN is the normal pace therefore the SAN is the normal pace maker of the heart, i.e its rate determine maker of the heart, i.e its rate determine the heart ratethe heart rate..

ElectrocardiographyElectrocardiography______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

It is recording of electrical events during the It is recording of electrical events during the cardiac cycle i.e., systole and diastolecardiac cycle i.e., systole and diastole..

Clinical ValueClinical Value::

11 - -Measures the heart rate/minMeasures the heart rate/min..

22 - -Identifies normal sinus rhythm (regularity)Identifies normal sinus rhythm (regularity)..

33 - -Diagnosis of arrhythmiasDiagnosis of arrhythmias..

44 - -Diagnosis of ischemia and infarctionDiagnosis of ischemia and infarction..

55 - -Diagnosis of electrolytes imbalanceDiagnosis of electrolytes imbalance..

Electrocardiogram (ECG)Electrocardiogram (ECG)______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

The electrical changes in the cardiac muscle The electrical changes in the cardiac muscle are recorded by electrodes of a special are recorded by electrodes of a special

instrument called electrocardiographyinstrument called electrocardiography . .

The record is the electrocardiogram (ECG)The record is the electrocardiogram (ECG)

Waves of normal ECGWaves of normal ECG::

P-wave: P-wave: atrial depolarizationatrial depolarization..

QRS-complex: QRS-complex: ventricular depolarizationventricular depolarization..

T-wave: T-wave: ventricular repolarizationventricular repolarization..

Electrocardiogram (ECG)Electrocardiogram (ECG)______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

Intervals of ECGIntervals of ECG::

P-R interval: P-R interval: 0.12-0.2 sec0.12-0.2 sec..

Interval between atrial depolarization and Interval between atrial depolarization and ventricular depolarization (A-V conduction)ventricular depolarization (A-V conduction)..

Q-T intervalQ-T interval;;

Interval from beginning of Q wave to end ofInterval from beginning of Q wave to end of

T wave (Whole period of depolarization and T wave (Whole period of depolarization and repolarization of the ventricle)repolarization of the ventricle)..

S-T segmentS-T segment::

From end of S wave to end of T waveFrom end of S wave to end of T wave . .

Cardiovascular System Week 9 Dr. Walid Daoud A. Professor.

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