Review of ECG Flashcards
what channel contributes to the diastolic depolarization?
funny channel
which channel is slow, depolarizing?
calcium
which channel is rapid, depolarizing?
sodium
which channel is responsible for repolarization?
potassium
what is the role of the funny channel? when is it closed?
allows positive charge to enter cell during repolarization / hyperpolarization
depolarization
what is the theme of phase 1 of cardiac AP?
early repolarization
what occurs during phase 1 of cardiac AP?
sodium channels close
some potassium channels open
repolarization incomplete
phase 2 of cardiac AP is due to what ion?
calcium
what is the membrane potential of cardiac AP phase 2?
approx zero
what occurs during phase 0 of cardiac AP? which ion / channel is responsible?
depolarization
fast sodium channels
what is the theme of phase 2 of cardiac AP?
plateau
what is the theme of phase 3 of cardiac AP?
rapid repolarization
what is occuring during phase 3 of the cardiac AP?
more calcium channels are closing opening of (more) potassium channels
what is the theme of phase 4 of the cardiac AP?
resting membrane potential
what is occurring during phase 4 of the cardiac AP? which channels are open?
resting potential maintained until next stimulus
only potassium channels are open
which phases are lacking in the nodal AP?
1 and 2
which channels open once threshold is reached in nodal AP?
calcium
during nodal AP, when do calcium channels open?
upon reaching threshold
are there fast sodium channels in nodal AP?
no
what occurs after max depolarization in nodal AP? which phase is this?
depolarizatino - potassium channels open
phase 3
what is the funny current in nodal AP? what is the result?
progressive reduction in potassium efflux
progressive increase in calcium influx
slowly depolarizes cell
what is the normal sequence of depolarization?
SA atria AV His bundle branches purkinje ventricles (septum - apex - ventricular free walls)
why does signal slow down at the AV node?
differences in connections between these cells - fewer cells
which part of the ventricles depolarize first?
septum
what are the bipolar limb leads?
I, II, III
what are the augmented unipolar limb leads?
aVR, aVL, aVF
what are the horizontal transverse plane chest leads?
V1 - V6
where is V1 located?
4th intercostal space, R sternal border
where is V2 located?
4th intercostal space, L sternal border
where is V4 located?
5th intercostal space, midclavicular line
where is V3 located?
between V2 and V4
where is V5 located?
in line with V4, anterior axillary line
where is V6 located?
in line with V4 and V5, midaxillary line (down from armpit)
what does the ST segment correspond to on the ECG?
phase 2 plateau
what does the QT segment correspond to on the ECG?
ventricular depolarization and repolarization
essentially the AP
what is the physiological correlate of the P wave?
atrial myocyte depolarization - phase 0
what is the physiological correlate of the QRS complex?
ventricular myocyte depolarization - phase 0
what is the physiological correlate of the PR interval?
all electrical events (depolarization - phase 0s) upstream of ventricular myocytes (atrial myocyte, AV node, bundle, bundle branches, purkinje)
what is the physiological correlate of the T wave?
ventricular myocyte repolarization - phase 3
what is the physiological correlate of the QT interval?
entire AP for ventricular myocytes (depolarization - plateau - repolarization)
what is the physiological correlate of the ST segment?
ventricular myocyte plateau - phase 2
