Cardiac Lecture 2 Flashcards
exam 4
The action potential of ______ tissue is considered a “Fast AP” because phase 0 slope is steep
Ventricular
Normal healthy heart rate
72bpm
Why is the SA node considered the pacemaker of the heart
It reaches threshold faster than anywhere else in the heart.
What is the magnitude of deflection of an EKG?
1.5mV
The mV between the lowest point and peak of R wave
What is the Vrm in the SA node?
-55mV
What is the threshold mV in SA node
-40mV
Which channel is responsible for the steep phase 4 in SA node action potential?
HCN
When do HCN channels open
Opens at Vrm or by cAMP
What ions can diffuse through HCN channel
Non-specific to + charged ions (cations). Primarily Na+ and Ca++ enter cell. (K+ can technically leave through, but usually leaves elsewhere)
What is an HCN channel
Hyperpolarization cyclic nucleotide channel
EKG is the sum of all _____ of cardiac electrical activity
current
Vrm in ventricular myocyte
-80mV
Peak of AP in ventricular myocyte
+20mV
1 big box on EKG is _____ mV
0.5mV
1 big box on EKG is ____ sec/msec
0.2 seconds/ 200ms
what is occuring at the P wave?
atrial depolarization
what is occuring at the QRS
ventricular depolarization and atrial repolarization (can’t see atrial repolarization because of ventricular depol)
What is occuring at the T wave
ventricular repolarization
Electrons moving _______ the positive lead results in a positive deflection
towards
Electrons moving _______ the positive lead results in a negative deflection
away
Electrons moving ______ the negative leads results in a negative deflection
towards
Electrons moving _______ the negative lead results in a positive deflection
away
Depolarization occurs first in the ________ and spreads _______ towards the ________
endocardium, superficially, epicardium
Repolarization occurs first in the _______ and spread _______ towards the _______
epicardium, deep, endocardium