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Lecture 3 – Continuing Cardiovascular system

Lecture 3 – Continuing Cardiovascular...

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Lecture 3 – Continuing Cardiovascular system Control of heart rate and the Cardiac cycle o Specialized conduction system o Specialized cell types o intrinsic rhythmicity (innate, endogenous HR) o Extrinsic Rhythmicity (response to exogenous influences) Cardiac Conduction system in mammals (humans) o o base (referring primarily to ventricles) everything above the base refers to the atrial tissue and large arteries o apex: bottom tip o black and yellow = specialized conduction system o system begins at SA node (sinoatrial node ) a single cell in the SA node is the pace maker single cell also generates action potential o Atrioventricular node (AV) = carries signal from SA node to rest of heart carries signal from atria to ventricles o Internodal Pathways: tracks of specialized cells from the SA node to the AV node o Interatrial pathway : takes action potentials generated in right atrium to left atrium all the diverging pathways converge onto AV node base Apex Slide 1 Slide 2
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all the cells and specialized pathways represent modified muscle cells –these are NOT neurons , nothing neuro--!!! these are myocytes (muscle cells) but the specialized conduction system in the heart is influenced by the nervous system autonomic NS innervates most of the cells w/n the heart pathway o sympathetic or parasympathetic division How the Heart works o action potential generated in single cell in SA node (impulse generated) o that cell causes firing of other cells in SA node, atria, and AV node o action potential passes through bundle of His—the left and right bundle branches then goes to the Purkinje fibers which take the AP to other regions of ventricles Sequence of depolarization, originating in SA node, in cardiac tissue o #1 – shows depolarized SA node and #2 – 6 shows the pathway of the AP from the SA node through the heart o Depolarization preceeds contraction o Action Potential Pathway: starts at SA, depolarizes regions of atrium passes to AV node passes through interventricular septum from the lateral walls of the septum, towards the interior of the septum o septum = vertical middle line of heart depolarization preceeds contraction one of the effects caused by depolarization of interventricular septum is that it contracts little earlier than other ventricular regions contraction of septum stabilizes the heart and holds it in place during contraction of AP once AP reaches apex of the heart, it goes out to the walls of ventricles progressing from the endocardium to the epicardium epicardium: inner most layer of the wall endocardium: outer most layer ventricular free walls eventually get depolarized from endocardium to epicardium and from apex to base o heart contracts (compresses) from apex to base: pushes blood from apex to base think about toothpaste example! Slide 3
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Lecture 3 – Continuing Cardiovascular...

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