Review of ECG Flashcards
What are the Cardiac musle Cell membrane transporters? Functions?
Fast Depolarizing Na Channels
Slow Depolarizing Ca++ Channels
Repolarizing K+ Channel
Funny Cation Channel- hyperpolaization (+ Charge enters cell during repolarizaion/ hyperpolarization)
What happens during Phase 0 of the Cardiac action potential?
Depolarization - Fast due to opening of Na Channels
What happens during Phase 1 of the Cardiac action potential?
Early repolarization
- Na channels close, some K channels open
- repolarization incomplete
What happens during Phase 2 of the Cardiac action potential?
Plateau
- Membrane potential Approx Zero
- due to slow Ca Channels
- Requires concurrent movement opposite to Ca
- Allows blood to be ejected from the heart
What happens during Phase 3 of the Cardiac action potential?
Rapid Repolarization
-More Ca Channels are closing, opening of more potassium chanels
What happens during Phase 4 of the Cardiac action potential?
Resting membrane potential
- only K channels are open
- resting potential maintained until next stimulus
What happens during Phase 0 of the Nodal Tissue action potential?
Thresholdpotential is met, Ca channels are opened,
- NO fast Na Channels
- slow response
What happens during Phase 3 of the Nodal Tissue action potential?
After Depolarization
K channels open
What happens during Phase 4 of the Nodal Tissue action potential?
Funny Current Slowly depolarizes cells
- progressive reduction in K efflux
- progressive increase in Ca influx
What is the sequence of depolarization in the heart?
SA node Atria AV Node Bundle of His Bundle Branches Purkinjie Fibers Ventricles 1. Septum 2. Apex 3. Ventricular free walls
What are the relative conduction velocities of the different tissue types in the heart?
AV node is slow-down(.02-.05)
Bundle Branches and Purkinje Fibers fast transmission(2-4m/s)
What is the Pacemaker rate of each individual tissue type in the heart?
SA node - 60-100 Atria - none AV Node - 40-55 Bundle of His - 25-40 Bundle Branches - 25-40 Purkinjie Fibers - 25-40 Ventricles - none
Where is the perspective of the recorded elelctrical activity of the heart taken from?
The surface of the heart
Which leads look ate the heart from the frontal plane?
Standard bipolar limb leads: I, II, III
Augmented unipolar limb leads: aVR, aVL, aVF
Which leads look at the heart from the Horizontal (Transverse) Plane?
Chest Leads
V1, V2, V3, V4, V5, V6 (+)
