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Lecture 2

CHSC 3P90 - Lecture 2- Electrical Activity of the Heart.docx

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Health Sciences
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Deborah O' Leary

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CHSC 3P90Lecture 2 Electrical Activity of the Heart Electrical PropertiesAutomaticityability of specialized cells to initiate an electrical impulse spontaneously Excitabilityability of cardiac cells to respond to an electrical impulseMechanical PropertiesConductilityability to transmit an impulse from one cardiac cell to anotherContractilityability of cardiac cells to contract after receiving an electrical impulseSinoatrial SA NodeAutorhythmic o Can initiate an impulse in its ownKnown as the pacemaker nodeLocatedin the right atrium Carries impulse wave that it generates to the atrioventricular AV node via intermodal pathwaysAtrioventricular AV NodeLocated in the right atrium near the bottom close to the ventricleMajor function o Provides a signal delay 00601 s to prevent the signal from travelling to the ventricles too rapidly Gives the ventricles time to fill up One way conduction prevents reentry of the impulses form the ventricle Maintains HR of 4060 BPM Buindle of His AV BundleThin bundle of threads connecting the AV node to the bundle branchesLocated in the right side of the interatrial septum just above the ventriclesLeft and Right Bundle BranchesTransmit impulses along the interventricular septum to the apex of the heartThey then split into smaller branches called purkinje fibres Purkinje FibresThey are conduction fibresLocated in the right and left ventricles causing depolarizationImpulse transmission is rapid at purkinje fibres 150x greater than the AV nodeThey innervate very few cardiac myocyteso Gap junctions transmit the signal from one cell to another meaning only minor innervations is requiredSequence of Depolarization1 SA node 2 AV node a AV junction cases a delay of 01 s allowing the atrium to contract and empty into the ventricles before the next contractionstimulationb AV nodeGatekeeper of conduction form the atria to the ventriclesi Limits rate of ventricular contraction during rapid atrial rhythms
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