Exam 1 Flashcards
Equation for Work
Work = Pressure X Volume
Effective Refractory Period
period of NO AP regardless of signal sent in the heart
Relative Refractory Period
period after EFP (near end of plateau phase 2) that requires stronger signal to stimulate another AP – moving subsequent AP closer together
Parasympathetic Effects on Heart
Vagal nerve innervates SA node and AV fibers proximal to AV node – vagal stimulation releases ACh which increases permeability of K+ causing hyper polarization
lower resting membrane potential makes it longer for the cell to depolarize therefore less AP firing and lower HR
Sympathetic Effects on Heart
NE causes increase in permeability of depolarizing ions (Na and Ca) therefore faster depolarization and increase HR
PR interval
atrial depolarization time (beginning of atrial depolarization to beginning to ventricular depolarization)
p wave to beginning of QRS
RR interval
time between on heart beat
QT interval
full cycle of ventricular contraction from depolarization to repolarization
ST interval
Time between end of ventricular depolarization and beginning to ventricular repolarization
Rough directions for conductivity of heart
Lead I, Lead II, and aVF
V1
right 4th intercostal space
V2
left 4th intercostal space
V4
5th intercostal space at midclavicular line
V3
between V2 and V4
V6
5th intercostal space at midaxillary line
V4
between V4 and V6
Right Axis Deviation
- LV failure
- hypertrophy of right ventricle (thus more current would flow there
First Degree AV incomplete block
- DELAY (not block) above bundle of His
- prolonged PR interval that is greater than 0.20 seconds
(normally 0.16s) but not higher than 0.35 seconds
Second degree AV Block
-block above or below bundle of His
- some signals get conducted and some do not
sinus is still firing regularly, so p wave (depolarization) signal may or may not be conducted
-ECG shows periodic drops of heart beat (can be every other or every third)
Third Degree AV block
total block at the AV node – leading to Stokes Adam’s Syndrome
- ventricles stop contracting for 30s due to “overdrive suppression”
