cardiac

Circulatory systemPressure gradients move blood through the heart and vessels.

Pulmonary circulation vs. systemic circulation

1

headand arms(to pulmonarycircuit)aorta(frompulmonarycircuit)heartother organsdiaphragmliverintestineslegsDouble pump both ventricles pump an equal volume of blood into systemic and pulmonary circuits

Higher resistance through the systemic circuitPressure - force exerted by pumped blood on a vessel wall

Resistance - opposition to blood flow from friction

venacavaRight atriumTricuspid valvevena cavaRight ventricle

Pulmonarysemilunar valveLeft pulmonaryarteryRight pulmonaryarteryRight atriumTricuspid valveRight ventricle

AortaLeft atriumRightpulmonary veinLeft pulmonaryveinBicuspid valveLeft ventricle

AortaLeft pulmonaryveinRightpulmonary veinAortic semilunarvalveLeft atriumLeft ventricle

When pressure is greater behind the valve, it opens.When pressure is greater in front of the valve, it closesValves ensure one-way flow

Leakproofseamssemilunar valve

Right atriumTricuspid valveRight ventriclePapillary muscle contracts with ventricleChordae tendineaeSeptumShape of the AV valves is maintained by chordae tendineaeVentricularVentricular Systole Diastole

Blood pressure variation

Heart myocardiumCardiac muscle fibers are interconnected by intercalated discs.

DesmosomeGap junctionIntercalated discActionpotentialJunctions between cardiac muscle cells

Pacemaker activitySlow depolarizations set off action potentials in a cycle

Pacemaker cellSpontaneous action potential

Action potential spreadto other cellsGap junctionsCardiac muscleSelf-excitable muscles - action potential gradually depolarizes, then repolarizesGap junctionsNo gap junctions between atria and ventricles

Fibrous insulating tissue prevents AP from directly spreading from atria to ventricles

Sinoatrial(SA) nodePurkinjefibersAtrioventricular(AV) nodePacemaker locations:

SA node

AV node

Bundle of His

Purkinje fibersConduction of contractionBundle of His

Problems with heart rateAV node rhythm is slower - bradycardia

Heart block a type of bradycardia. Ventricles pump slowly and out of rhythm of atria Problems with heart rate

Problems with heart rate

Ventricular fibrillation

Atrial fibrillation

PlateauphaseThresholdpotentialAction potential in cardiac muscle

ActionpotentialContractionRefractoryperiodLong refractoryperiod ensures nosummation of twitches

Relaxation of cardiac muscles is requiredElectrocardiogram (ECG or EKG)Currents from electrical activity of heart spread to body tissues and fluidThis electrical activity is detected by electrodes and transformed to waveforms

PRQSTPPRSTTP interval

time (seconds)bradycardiatachycardiaventricularfibrillation

Ventricular and atrial diastoleCardiac cycle25

Atrial contractionCardiac cycle

Isovolumetric ventricular contractionCardiac cycleLubEnd diastolic volumeis in the ventricles

Ventricular ejectionCardiac cycle

Isovolumetric ventricular relaxationCardiac cycleDubEnd systolic volumeis in ventricles

Systolic or diastolic murmurs

Often due to stenosis or regurgitation at a valve (whistle vs. swish)

Normal heart lub-dup

Diastolic mitral stenosislub-dup-whistle

Diastolic aortic regurgitationlub-dup-swish

Systolic aortic stenosislub-whistle-dupSystolic tricuspid regurgitationlub-swish-dup

Diastolic patent ductus arteriosusWhat are heart murmurs?

Extrinsically: conduction speed

contraction strengthSympathetic signals increase stroke volume

Optimal lengthEnd-diastolic volume (EDV) (ml)Normal resting lengthIncreasein SVStroke volume (SV) (ml)B1A1Increasein EDVFrank Starling law(intrinsic increase in stroke volume)Would you expect type 1 or type 2 fibers in heart muscle?Cardiac muscle cells are highly resistant to fatigueMany mitochondria, larger mitochondria, myoglobin, high vascularization.Mitochondria convert lactate pyruvate glucose

Mitochondria

How does the heart regulate its contration?Heart diseaseWhat is a heart attack, what causes it?Why some heart attacks worse than others?

Heart failureDue to: Poor circulation to heart muscle (blockage)High blood pressure makes heart work harder

Insufficient valve

Less bloodleaving39Heart failureContinued sympathetic action can temporarily alleviate heart failure effects on output

Kidney fluid retention thus stroke volume

Stroke volume is so low that blood backs up in blood vessels leading to heart

Failure on left side - blood collects in pulmonary circuit and causes pulmonary edema. Oxygenation decreases.

Response of kidneys to fluid retention is now problematic.Congestive heart failureDue to thickening of heart muscle:To pump against high pressureLeaking or stiffness in heart valves

Due to over-dilation due bc of heart failure (usually pulmonary edema)

What causes an enlarged heart?

Heart attacks, strokes

Blockage due to plaques, embolismsArteriosclerosis

smooth musclepart of plaquevessel wallEndotheliumLipid centerof plaquePlaques in blood vesselsLDLs, inflammation contribute to plaque formationCholesterol carried in the blood:High-density lipoprotein - helps move cholesterol back to liver for removal

Low-density lipoprotein - used by cells, excess LDL infiltrates artery walls

Saturated fats and trans fats raise LDLs and are atherogenic

Free radicals oxidize LDLs and make them more likely to attach to plaques

blockagegraftedarteriesCoronary bypass