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The Hearts External Anatomy & Conduction System. Heart at rest Heart at rest Blood flows from large veins into atria Blood flows from large veins into.

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Presentation on theme: "The Hearts External Anatomy & Conduction System. Heart at rest Heart at rest Blood flows from large veins into atria Blood flows from large veins into."— Presentation transcript:

1 The Hearts External Anatomy & Conduction System

2 Heart at rest Heart at rest Blood flows from large veins into atria Blood flows from large veins into atria Passive flow from atria into ventricles Passive flow from atria into ventricles Atria (R & L) contract simultaneously Atria (R & L) contract simultaneously Blood forced into ventricles Blood forced into ventricles Ventricles (R & L) contract simultaneously Ventricles (R & L) contract simultaneously Atrioventricular valves close lubb sound Atrioventricular valves close lubb sound Blood forced into large arteries Blood forced into large arteries Ventricles relax Ventricles relax Semilunar valves close dub sound Semilunar valves close dub sound Heart at rest Heart at rest

3 HEART Pericardium Membrane sac Surrounds the heart Protection Anchors Contains serous fluid Pericarditis inflammation of the pericardium decreases serous fluid causing painful adhesions interfering with heart movements

4 Heart Wall Epicardium (outside) – visceral layer of the serous pericardium. Epicardium (outside) – visceral layer of the serous pericardium. Myocardium (muscle) – cardiac muscle layer forming the bulk of the heart. Myocardium (muscle) – cardiac muscle layer forming the bulk of the heart. Endocardium (within) – endothelial layer of the inner myocardial surface. Endocardium (within) – endothelial layer of the inner myocardial surface.

5 Cardiac Muscle Specialized muscle cells Specialized muscle cells Involuntary Involuntary Striated Striated Cushioned by endomysium Cushioned by endomysium Joined by intercalated discs Joined by intercalated discs Cardiac cell metabolism Cardiac cell metabolism Areobic Areobic Large mitochondria Large mitochondria Organic fuels: fatty acids & glucose Organic fuels: fatty acids & glucose Fatigue resistance Fatigue resistance

6 Left coronary artery supplies left atrium and left ventricle Anterior interventricular artery supplies both ventricles Right coronary artery supplies right ventricle Posterior interventricular artery supplies both ventricles Coronary Arteries Branch off aorta above aortic semilunar valve

7 Collects wastes from cardiac muscle Drains into a large sinus on posterior surface of heart called the coronary sinus Coronary sinus empties into right atrium Coronary Veins

8 The heart beats because of the spread of electrical impulses to the heart muscle, causing it to contract.

9 Cardiac muscle tissue exhibits autorhythmicity = generates its own stimulation. 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. This is possible because of an internal cardiac conduction system which can initiate and distribute electrical impulses. Cardiac Conduction System

10 Comprised of interconnected structures Comprised of interconnected structures Sinoatrial node Sinoatrial node Atrioventricular node Atrioventricular node Atrioventricular Bundle Atrioventricular Bundle Bundle Branches Bundle Branches Purkinje Fibres Purkinje Fibres Cardiac Conduction System

11 Sinoatrial (SA) Node

12 Junction of atria and ventricles Junction of atria and ventricles Spread of depolarisation - from atrial myocardium Spread of depolarisation - from atrial myocardium Delay 0.15 seconds Delay 0.15 seconds Time atria to expel blood Time atria to expel blood Time for ventricular filling Time for ventricular filling Protection to ventricles Protection to ventricles Less autonomic nervous control than SA node Less autonomic nervous control than SA node Sympathetic conduction time Sympathetic conduction time Parasympathetic conduction time Parasympathetic conduction time Atrioventricular (AV) Node Atrioventricular node

13 Linked to the nervous system

14 Depolarization begins Depolarization begins in sinoatrial (SA) node Spread through atrial myocardium Spread through atrial myocardium Results in myocardial contration of the atria Results in myocardial contration of the atria Delay in atrioventricular (AV) node Delay in atrioventricular (AV) node To the Bundle of His To the Bundle of His AKA atrioventricular bundle AKA atrioventricular bundle Depolorization The heart is autorhythmic

15 Separates into 2 main Separates into 2 main branches left & right Located in the interventricular septum Located in the interventricular septum Left bundle – antero-superior division Left bundle – antero-superior division Right bundle – postero-inferior division Right bundle – postero-inferior division Bundle branches divide - small, dense network of conduction tissue called the Purkinje Fibers Bundle branches divide - small, dense network of conduction tissue called the Purkinje Fibers Entire musculature depolarizes quickly Depolorization The heart is autorhythmic

16 Variations in electrical potential radiate from the heart ECG records electrical events in the heart. Electrocardiogram

17 P wave Depolarization of atria Followed by contraction QRS complex 3 waves (Q, R, & S) Depolarization of ventricles Followed by contraction T wave Repolarization of ventricles P-Q interval Time atria depolarize & remain depolarized Q-T interval Time ventricles depolarize & remain depolarized P-P = one cardiac cycle P-Q = time for atrial depolarization Q-T = time for ventricular depolarization T-P = time for relaxation

18 SA node Represented on the ECG as P wave AV node conduction is represented on the ECG as the PR Interval The Bundle Branch and purkinje fibre depolarisation constitutes ventricular depolarisation Represented on the ECG as the QRS Atrial repolarisation occurs within the QRS & therefore is masked Ventricular repolarisation is represented on the ECG as a T wave P PR T QRS

19 1) atrial depolarization begins 2) atrial depolarization complete (atria contracted) 3) ventricles begin to depolarize at apex; atria repolarize (atria relaxed) 4) ventricular depolarization complete (ventricles contracted) 5) ventricles begin to repolarize at apex 6) ventricular repolarization complete (ventricles relaxed)


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