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Transcript of Advanced Cardiac Care in the Streets Understanding EKGs Ray Taylor Valencia Community College...
Advanced Cardiac Care in the StreetsUnderstanding EKGs
Ray Taylor Valencia Community College
Advanced Cardiac Care in the StreetsUnderstanding EKGs
Ray Taylor Valencia Community College
ElectrophysiologyElectrophysiology
NoticeNotice
All rights reserved. All rights reserved. Slide show used with permission only for the Slide show used with permission only for the
purposes of educating emergency medical providers purposes of educating emergency medical providers (EMTs and Paramedics) (EMTs and Paramedics)
No portion of this presentation may be reproduced, No portion of this presentation may be reproduced, stored in a retrieval system in any form or by any stored in a retrieval system in any form or by any means (including but not limited to electronic, means (including but not limited to electronic, mechanical, photocopying etc.) without prior written mechanical, photocopying etc.) without prior written permission from the authorpermission from the author
Basic ElectrophysiologyBasic Electrophysiology
ObjectivesObjectives State the two basic myocardial cell groupsState the two basic myocardial cell groups Describe the function of each myocardial Describe the function of each myocardial
cell groupcell group Discuss the four primary properties of Discuss the four primary properties of
cardiac cellscardiac cells List the three major electrolytes that affect List the three major electrolytes that affect
cardiac functioncardiac function
Basic ElectrophysiologyBasic Electrophysiology
Objectives [ continued ]Objectives [ continued ] Describe the movement of ionsDescribe the movement of ions Describe cardiac depolarizationDescribe cardiac depolarization Describe cardiac repolarizationDescribe cardiac repolarization Define refractory periodDefine refractory period Describe the absolute refractory periodDescribe the absolute refractory period Describe the relative refractory periodDescribe the relative refractory period
Cardiac PhysiologyCardiac Physiology
ElectrophysiologyElectrophysiology Cardiac MuscleCardiac Muscle
AtrialAtrial VentricularVentricular Excitatory and Excitatory and
Conductive FibersConductive Fibers Intercalated discsIntercalated discs SyncytiumSyncytium
Atrioventricular Atrioventricular BundleBundle
DepolarizationDepolarization
Basic Cell GroupsBasic Cell Groups
Specialized Pacemaker CellsSpecialized Pacemaker Cells do not have the ability to contractdo not have the ability to contract responsible for controlling rate and rhythm responsible for controlling rate and rhythm
by coordinating regular depolarizationby coordinating regular depolarization found in electrical conduction system of the found in electrical conduction system of the
heartheart primary function is generation and primary function is generation and
conduction of electrical impulsesconduction of electrical impulses
Basic Cell GroupsBasic Cell Groups
The Myocardial Working CellsThe Myocardial Working Cells responsible for generating the physical responsible for generating the physical
contraction of heart cellscontraction of heart cells muscular layer of atrial walls and thicker muscular layer of atrial walls and thicker
muscular layer of ventricular wallsmuscular layer of ventricular walls primary functions are both contraction and primary functions are both contraction and
relaxationrelaxation physical contraction of myocardial tissue physical contraction of myocardial tissue
actually generates blood flowactually generates blood flow
Basic Cell GroupsBasic Cell Groups
ThresholdThreshold - - point at point at which a stimulus will which a stimulus will produce a cell responseproduce a cell response
““All or None” All or None” phenomenonphenomenon - stimulus - stimulus is strong enough for is strong enough for cardiac cells to reach cardiac cells to reach threshold, ALL cells will threshold, ALL cells will respond to this stimulus respond to this stimulus or none will respond.or none will respond. SyncytiumSyncytium
Cardiac PhysiologyCardiac Physiology
Cardiac Cell Cardiac Cell CharacteristicsCharacteristics
PropertiesProperties AutomaticityAutomaticity ExcitabilityExcitability ConductivityConductivity ContractilityContractility
Primary Cardiac Cell CharacteristicsPrimary Cardiac Cell Characteristics
1. 1. AutomaticityAutomaticity - [ electrical function ] - [ electrical function ] ability of cardiac pacemaker cells to ability of cardiac pacemaker cells to spontaneously generate own electrical spontaneously generate own electrical impulses without external stimulation impulses without external stimulation
2. Excitability2. Excitability - [ electrical function ] - [ electrical function ] ability of cardiac cells to respond to ability of cardiac cells to respond to electrical stimulus is also referred to as electrical stimulus is also referred to as irritabilityirritability
Primary Cardiac Cell CharacteristicsPrimary Cardiac Cell Characteristics
3.3. ConductivityConductivity - [ electrical function ] ability of - [ electrical function ] ability of cardiac cells to receive an electrical stimulus cardiac cells to receive an electrical stimulus and then to transmit the stimulus to other and then to transmit the stimulus to other cardiac cells, so they function collectively as cardiac cells, so they function collectively as a unita unit
4. 4. ContractilityContractility - [ mechanical function ] also - [ mechanical function ] also referred to as rhythmicity, is the ability of referred to as rhythmicity, is the ability of cardiac cells to shorten and cause cardiac cardiac cells to shorten and cause cardiac muscle contraction in response to an muscle contraction in response to an electrical stimulus electrical stimulus
Major Electrolytes That Affect Cardiac FunctionMajor Electrolytes That Affect Cardiac Function
Myocardial cells bathed in electrolyte Myocardial cells bathed in electrolyte solutionssolutions ElectrolyteElectrolyte - substance or compound - substance or compound
whose molecules dissociate into charged whose molecules dissociate into charged components, orcomponents, or ionsions. .
Produce + charged ions [ Produce + charged ions [ cationcation ] and ] and
- charged ions [ - charged ions [ anionanion ] when placed in ] when placed in waterwater
Three Major Cations That Affect Cardiac FunctionThree Major Cations That Affect Cardiac Function
PotassiumPotassium [ [KK+] - performs major +] - performs major function in cardiac depolarization and function in cardiac depolarization and repolarizationrepolarization
SodiumSodium [[NaNa] - performs vital part in ] - performs vital part in depolarization of myocardiumdepolarization of myocardium
CalciumCalcium [[CaCa] - important function in ] - important function in depolarization and myocardial depolarization and myocardial contractioncontraction
Movement of IonsMovement of Ions
Ionic difference on two sides of cellIonic difference on two sides of cell Potassium ionPotassium ion -concentration greater inside cell -concentration greater inside cell Sodium ionSodium ion -concentration greater outside cell -concentration greater outside cell Sodium-potassium exchange pumpSodium-potassium exchange pump - active - active
transport, potassium / sodium moved in and out of transport, potassium / sodium moved in and out of cell through cell membranecell through cell membrane
During During polarized or resting statepolarized or resting state, inside of cell , inside of cell electrically negative relative to outside of cellelectrically negative relative to outside of cell
Cardiac DepolarizationCardiac Depolarization
When impulse develops and spreads When impulse develops and spreads throughout the myocardium, changes occur in throughout the myocardium, changes occur in heart muscle fibersheart muscle fibers Cardiac DepolarizationCardiac Depolarization - sodium ions rush into - sodium ions rush into
cell (fast channel), changing interior charge to + cell (fast channel), changing interior charge to + after cell stimulatedafter cell stimulated
Calcium enters slow channel maintaining contractionCalcium enters slow channel maintaining contraction
Cardiac RepolarizationCardiac Repolarization - sodium ions return to - sodium ions return to outside of cell, potassium returns to inside of celloutside of cell, potassium returns to inside of cell
Cardiac Physiology/Ion ShiftsCardiac Physiology/Ion Shifts
Cardiac Cardiac DepolarizationDepolarizationResting PotentialResting PotentialAction PotentialAction PotentialRepolarizationRepolarization
Terms to RememberTerms to Remember
Resting Resting MembraneMembrane PotentialPotential - state of - state of cardiac cell- inside cardiac cell- inside negative-outside negative-outside positivepositive
Action PotentialAction Potential - - change in polarity; change in polarity; produces change in produces change in cell electrical charge cell electrical charge caused by caused by stimulation of stimulation of myocardial cellsmyocardial cells
Terms to RememberTerms to Remember
SyncytiumSyncytium - - cardiac muscle cell cardiac muscle cell groups that are groups that are connected together connected together and function as a and function as a unitunit
Polarized StatePolarized State - - resting state of resting state of cardiac cell, inside cardiac cell, inside of cell is electrically of cell is electrically negative relative to negative relative to outsideoutside
Refractory PeriodsRefractory Periods
Attempts to ensure muscle is totally Attempts to ensure muscle is totally relaxed before another action potential relaxed before another action potential or depolarization can be initiatedor depolarization can be initiated
Atrial muscleAtrial muscle = 0.15 sec. = 0.15 sec. Ventricular muscleVentricular muscle = 0.25 to 0.3 sec. = 0.25 to 0.3 sec. Period of rest is referred to asPeriod of rest is referred to as
Cardiac RepolarizationCardiac Repolarization
Two Stages of RepolarizationTwo Stages of Repolarization
Absolute Absolute RefractoryRefractory PeriodPeriod - cardiac cell unable - cardiac cell unable to respond to new to respond to new electrical stimulus, electrical stimulus, cannot cannot spontaneously spontaneously depolarizedepolarize
Two Stages of RepolarizationTwo Stages of Repolarization
Relative RefractoryRelative Refractory PeriodPeriod - - repolarization repolarization is almost complete, is almost complete, cardiac cell can be cardiac cell can be stimulated to contract stimulated to contract prematurely if stimulus prematurely if stimulus is stronger than normalis stronger than normal
Thank you!