Presentation on theme: "The Heart’s External Anatomy & Conduction System"— Presentation transcript:
1 The Heart’s External Anatomy & Conduction System
2 Atria (R & L) contract simultaneously Heart at restBlood flows from large veins into atriaPassive flow from atria into ventriclesAtria (R & L) contract simultaneouslyBlood forced into ventriclesVentricles (R & L) contract simultaneouslyAtrioventricular valves close “lubb” soundBlood forced into large arteriesVentricles relaxSemilunar valves close “dub” sound
3 Pericardium Membrane sac Surrounds the heart Protection Anchors Contains serous fluidHEARTPericarditisinflammation of the pericardium decreases serous fluid causing painful adhesions interfering with heart movementsA 2 layered bag the outer layer is called the fibrous pericardium and the serous pericardiumThe fibrous pericardium anchors the heart to surrounding structures like the diaphragm and the sternum.The serous pericardium secrets a fluid contained within the pericardium allows the heart to beat easily in a relatively frictionless environmentPericarditis is when the pericardium becomes inflamed causing the layers of the sac to stick to each other and interfere with heart movemntsPericardium
4 Heart WallEpicardium (outside) – visceral layer of the serous pericardium.Myocardium (muscle) – cardiac muscle layer forming the bulk of the heart.Endocardium (within) – endothelial layer of the inner myocardial surface.Remember “visera” means internal part of a structure or the organsThe bulk of the walls of the heart is the myocardium which consists of thick bundles of cardiac muscle twisted and whorled into ringlike arrangements. This is the layer that actually contractsThe endocardium is a thin membrane that lines the heart chambers.Endocarditis is inflammation of this lining – what sorts of problem could this cause?
5 Cardiac Muscle Specialized muscle cells Involuntary Striated Cushioned by endomysiumJoined by intercalated discsCardiac muscle cells are branching cells that are joined by special junctions called intercalated discs, this along with the spiral arrangement of the muscle bundles allow heart activity to be closely coordinated.Why is it important the muscles of the heart be coordinated?The cardiac muscle cells are set up to be fatique resistant by having large mitochondria and having the ability to burn both sugar and fat for energyCardiac cell metabolismAreobicLarge mitochondriaOrganic fuels: fatty acids & glucoseFatigue resistance
6 Coronary Arteries Branch off aorta above aortic semilunar valve Left coronary arterysupplies left atrium and left ventricleAnterior interventricular arterysupplies both ventriclesRight coronary arterysupplies right ventriclePosterior interventricular artery
7 Coronary Veins Collects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart called the coronary sinusCoronary sinus empties into right atrium
8 The heart beats because of the spread of electrical impulses to the heart muscle, causing it to contract.
9 Cardiac Conduction System Cardiac muscle tissue exhibits autorhythmicity = generates its own stimulation.This is possible because of an internal cardiac conduction system which can initiate and distribute electrical impulses.
10 Cardiac Conduction System Comprised of interconnected structuresSinoatrial nodeAtrioventricular nodeAtrioventricular BundleBundle BranchesPurkinje Fibres
12 Atrioventricular (AV) Node Junction of atria and ventriclesSpread of depolarisation - from atrial myocardiumDelay 0.15 secondsTime atria to expel bloodTime for ventricular fillingProtection to ventriclesLess autonomic nervous control than SA nodeSympathetic ↑conduction timeParasympathetic ↓conduction timeAtrioventricularnode
13 Linked to the nervous system The cardiovascular center of the medulla oblongata connects to the SA & AV nodes directly via the vagus nerve (cranial nerve 10) as well as thru the spinal cord.Sensory information is sent to the cardiac center of the medulla which can illicit a parasympathetic response directly or a sympathetic response thru the spinal cord/Nervous control from the cardiovascular center in the medullaSympathetic impulses increase heart rate and force of contractionparasympathetic impulses decrease heart rate.Baroreceptors (pressure receptors) detect change in BP and send info to the cardiovascular center
14 Depolorization Depolarization begins in sinoatrial (SA) node The heart is autorhythmicDepolarization beginsin sinoatrial (SA) nodeSpread through atrial myocardiumResults in myocardial contration of the atriaDelay in atrioventricular (AV) nodeTo the Bundle of HisAKA atrioventricular bundleThe heart is autorythmic – it can carry impulses
15 Depolorization Entire musculature depolarizes quickly The heart is autorhythmicSeparates into 2 mainbranches left & rightLocated in the interventricular septumLeft bundle – antero-superior divisionRight bundle – postero-inferior divisionBundle branches divide - small, dense network of conduction tissue called the Purkinje FibersEntire musculature depolarizes quickly
16 ElectrocardiogramVariations in electrical potential radiate from the heartECG records electrical events in the heart.
17 P wave QRS complex T wave P-Q interval Q-T interval P-P = one cardiac cycleP-Q = time for atrial depolarizationQ-T = time for ventricular depolarizationT-P = time for relaxationP waveDepolarization of atriaFollowed by contractionQRS complex3 waves (Q, R, & S)Depolarization of ventriclesT waveRepolarization of ventriclesP-Q intervalTime atria depolarize & remain depolarizedQ-T intervalTime ventricles depolarize & remain depolarized
18 SA node Represented on the ECG as P wave QRSSA node Represented on the ECG as P waveAV node conduction is represented on the ECG as the PR IntervalThe Bundle Branch and purkinje fibre depolarisation constitutes ventricular depolarisation Represented on the ECG as the QRSAtrial repolarisation occurs within the QRS & therefore is maskedVentricular repolarisation is represented on the ECG as a T wave
19 1) atrial depolarization begins 2) atrial depolarization complete (atria contracted)3) ventricles begin todepolarize at apex;atria repolarize (atria relaxed)4) ventriculardepolarization complete(ventricles contracted)5) ventricles begin to repolarize at apex6) ventricular repolarization complete (ventricles relaxed)