basic principles of electrical potentials recorded from the body surface Heart dipole and ECG Einthoven triangle Flashcards
Why are EKG recorded
When the cardiac impulse passes through the heart, electrical current also spreads from the heart into the adjacent tissues surrounding the heart.
A small portion of the current spreads all the way to the surface of the body. If electrodes are placed on the skin on opposite sides of the heart, electrical potentials generated by the current can be recorded;
The normal electrocardiogram is composed of
P wave, a QRS complex, and a T wave.
The P wave is caused by electrical potentials generated when
atria depolarize before atrial contraction begins.
The QRS complex is caused by potentials generated when
the ventricles depolarize before contraction
both the P wave and the components of the QRS complex are
depolarization waves.
The T wave is caused by potentials generated as
ventricles recover from the state of depolarization.
Repolarisation occurs in ventricular muscles…… seconds after depolarisation
0.25-0.35
Magnitude (size) of deflection indicates
the number of charges moving.
The width of deflection represents
time interval of the event.
No potential is recorded when
cardiac muscle is completely depolarized or repolarized.
charges move perpendicular to the lead-axis.
ECG recording profile depends on the location of
the electrode
During depolarization of the heart the extracellular fluid surrounding the myocardium becomes more …… because…
negative,
positively charged ions (Na+ and Ca2+) enter cardiac myocytes.
Depolarization is the travelling ….. charges on the surface and travelling …. charges within the cells.
negative
Positive
A dipole is a ….
vector quantity
Magnitude of dipole depends on the ……. and direction is from the …….
amount of charge creating the dipole
negative charge center to the positive charge center
