PSIO 532 Study Guide - Midterm Guide: Sinus Rhythm, Atrioventricular Node, Qrs Complex
Graduate Physiology PSL
Diseased Wave Forms
➔ Describe how cell injury, resulting in a less negative resting potential, alters ionic events
in depolarization and repolarization. Predict the consequence of a failure to conduct the
impulse through any of these areas
➢ Does it have a normal sinus rhythm?
➢ What is the heart rate? → important in determining parasympathetic and
sympathetic
➢ Are the waves, intervals and segments normal? → is the SA node and the AV
node talking properly? Is the amount of time that its taking normal? Any change
in segment length that might indicate ischemia?
➢ What is the mean the electrical axis of the heart? Is it deviated?
Does it have a normal sinus rhythm?
• P wave of sinus origin
- Normal axis of the P-wave (this is where the SA node is firing and
depolarizing)
- Positive in lead II (depolarization is going directly at the positive
electrode), negative in VR (in VR, the positive electrode is by the
right shoulder, so this atrial depolarization would be going away
from that positive electrode)
- In lead II, the p-wave is positive, while in VR, the p-wave is negative
• Constant and normal P-R interval is less than 0.20 seconds
o If the interval is longer (delay) → 1st degree heart block
o If interval is not ALWAYS followed by a QRS → 2nd degree heart
block AV ode does’t odut a ipulse
o If its not associated with a QRS complex → 3rd degree heart block
(no conduction of atrioventricular node; QRS complexes being
conducted at their own rate and totally independent of the P
waves)
• Rate is between 60-100 bpm
• Constant P-P interval (varies less than 0.16 seconds)
What is the Heart Rate?
▪ R-R interval: it is the period between heart beats
▪ HR = [1/RR(sec)]*60
▪ There are 5 squares for every large square, so what you do is calculate the
number of big squares between the R-waves; then take that number of large
squares and use it to divide 300; this will get you the heart rate
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Describe how cell injury, resulting in a less negative resting potential, alters ionic events in depolarization and repolarization. Predict the consequence of a failure to conduct the impulse through any of these areas. Does it have a normal sinus rhythm: p wave of sinus origin. Normal axis of the p-wave (this is where the sa node is firing and depolarizing) Positive in lead ii (depolarization is going directly at the positive electrode), negative in vr (in vr, the positive electrode is by the right shoulder, so this atrial depolarization would be going away from that positive electrode) In lead ii, the p-wave is positive, while in vr, the p-wave is negative: constant and normal p-r interval is less than 0. 20 seconds. If the interval is longer (delay) 1st degree heart block. If interval is not always followed by a qrs 2nd degree heart block (cid:894)av (cid:374)ode does(cid:374)"t (cid:272)o(cid:374)du(cid:272)t a(cid:374) i(cid:373)pulse(cid:895)
