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Jonctiunea (sinapsa electrica) neuro-
muscularaPotentialul electric de actiune
Semnalul electrocardiografic
Fibra cardiaca-dipol electric
Electrocardiograma
MODELUL VECTORIAL
Activitatea electrica a
tesutului muscular cardiac
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1. Terminatie nervoasa
2. Sarcolema=membrana celuleimusculare
3. Vezicula cu neurotransmitator
4. Receptor membranar de
acetilcolina (neurotransmitator)
5. Mitocondriile
Jonctiunea (sinapsa
electrica) neuro-
musculara
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Canale ionice implicate in stimularea electrica
(excitatia) celulelor musculare de catre celulele
neuronale
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Muschiul cardiac cu fibre
purkinje fibre cardiace
modificate care isi au originea in
nodul atrioventricular si se
ramifica in ambele ventricule.Aceste fibre transmit impulsul
electric de la nodul
atrioventricular catre ventricules
facand posibila contractiasimultana.
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Electrocardiogram (ECG/EKG)
Is a recording of electrical activity of heart conducted throw ionsin body to surface
Fig 13.22a
13-60
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Elements (parameters) of ECG signal
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3 distinct waves are
produced during
cardiac cycle
P wavecaused by
atrial depolarization
QRS complex
caused by
ventricular
depolarization
T waveresults from
ventricularrepolarization
ECG
Fig 13.2413-63
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Elements of the ECG:
P wave: Depolarization of both atria;
Relationship between P and QRS helps distinguish various cardiacarrhythmias
Shape and duration of P may indicate atrial enlargement
PR interval: from onset of P wave to onset of QRS
Normal duration = 0.12-2.0 sec (120-200 ms) (3-4 horizontal boxes)
Represents atria to ventricular conduction time (through His bundle)Prolonged PR interval may indicate a 1st degree heart block
QRS complex: Ventricular depolarization
Larger than P wave because of greater muscle mass of ventricles
Normal duration = 0.08-0.12 seconds
Its duration, amplitude, and morphology are useful in diagnosing
cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte
derangement, etc.
Q wave greater than 1/3 the height of the R wave, greater than 0.04
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ST segment:
Connects the QRS complex and T waveDuration of 0.08-0.12 sec (80-120 msec
T wave:
Represents repolarization or recovery of ventriclesInterval from beginning of QRS to apex of T is
referred to as the absolute refractory period
QT Interval
Measured from beginning of QRS to the end of the T
wave
Normal QT is usually about 0.40 sec
QT interval varies based on heart rate
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Fig. 13.24b
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Fig. 13.24c
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Fig. 13.24d
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Elements of the ECG:
P waveDepolarization of both atria;
Relationship between P and QRS helpsdistinguish various cardiac arrhythmias
Shape and duration of P may indicate atrialenlargement
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QRS complex:
Represents ventricular depolarization
Larger than P wave because of greater muscle mass of ventricles
Normal duration = 0.08-0.12 seconds
Its duration, amplitude, and morphology are useful in diagnosing
cardiac arrhythmias, ventricular hypertrophy, MI, electrolyte
derangement, etc.
Q wave greater than 1/3 the height of the R wave, greater than 0.04
sec are abnormal and may represent MI
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PR interval:
From onset of P wave to onset of QRS
Normal duration = 0.12-2.0 sec (120-200 ms) (3-4
horizontal boxes)
Represents atria to ventricular conduction time (through
His bundle)
Prolonged PR interval may indicate a 1st degree heart
block
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Fig. 13.24g
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T wave:Represents repolarization or recovery of ventricles
Interval from beginning of QRS to apex of T is referred to as theabsolute refractory period
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ST segment:Connects the QRS complex and T wave
Duration of 0.08-0.12 sec (80-120 msec
QT IntervalMeasured from beginning of QRS to the end of the T wave
Normal QT is usually about 0.40 sec
QT interval varies based on heart rate
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Modelul vectorial
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Modelul vectorial
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