ECG Flashcards
P wave
represents atrial depolarization
PR interval
Waves
Intervals and Segments
a. P wave represents atrial depolarization
b. PR interval represents depolarization from SA through AV node
c. QRS interval represents ventricle depolarization
d. Atrial repolarization occurs during the QRS wave so we cannot see it
e. ST segment represents depolarized ventricles
F. T wave represents ventricular repolarization
g. QT interval represents ventricular depolarization + repolarization
h. PT interval represents systole
i. PT segment represents diastole
Vertical axis is amplitude. Each box is 0.5 mv OR 5 mm.
Horizontal axis is time in seconds. Each box is 0.20 seconds and each small box is 0.04 seconds.
Mechanics Of The Electrocardiogram - ECG
Graphic recording of the electrical impulses produced by depolarization of the heart. The electrical current is passed to tissues and body surface; if electrodes are placed on the body. the transduced energy can be recorded on paper or oscilloscope (bedside or telemetry).
- Excitability
the ability to reach threshold and respond to an impulse or stimulus electrical irritability due to ionic imbalance across the cell membrane; the degree of intracellular negativity determines its excitability. ELECTRICAL
2 Automaticity
the ability to spontaneously initiate an impulse or stimulus caused by an increased permeability of the cell membrane to sodium (Na) & (Ca**) and flow of potassium (K) out of the cell. ELECTRICAL
conductivity
the ability to transmit (propagate) impulses to other areas - increased velocity due to intercalated disks. ELECTRICAL
contractility
- the ability to respond to this electrical impulse with pump action…..contraction. MECHANICAL
Refractoriness
altered responsiveness of cellular membrane to stimulus primarily dependent on influx and efflux of ions. ELECTRICAL
