EKG August 24-28

August 24-28: Depolarization/Repolarization of a Contactile Cell, Electrical Charges in the Heart, Standard and Augmented Limb Leads, Einthoven's Triangle
OBJECTIVES:
Be able to explain in detail the depolarization and repolarization timeline of a contractile cell in the heart
Be able to discuss electrical charges in the heart and how they are affected by the depolarization within the heart
Be able to identify and name different deflections in the QRS
Be able to exlain why there is a delay in electrical conduction at the AV node
Be able to draw and label the standard and augmented limb leads
Be able to draw and label Einthoven's triangle

Click Here to Download Exam 1 Part B due Friday August 28 by 12 Midnight

Note to Class: There are 3 Youtube Videos with this Week (see below):

Please watch this Youtube video below where we discuss the depolarization and repolarization timeline of a heart contracticle cell.
Click here for the Depolarization/Repolarization Timeline YOUTUBE video

Ventricular Contractile Cell Depolarization & Repolarization

Phase 4: Restoring with the Na+K+ pump (Na+ extracellular, K+ intracellular), RMP is -90mV
Phase 0: Depolarization; Influx of Na+ through FAST Na+ channels
Phase 1: Early Rapid Repolarization: K+ efflux, Fast Na+ channels close
Phase 2: Slow Repolarization (plateau phase): K+ efflux, influx of Ca++ and Na+ (SLOW Na+ channels)
Phase 3: Final Rapid Repolarization: K+ efflux, Ca++ and SLOW Na+ channels close

Electrical Charges in the Heart

To understand the direction and magnitude of Electrical charges in the heart, please watch this YOUTUBE video. It also explains the delay of conduction at the AV Node.

Click here to watch a YOUTUBE lectute on Electrical Charges in the Heart

Remember. When the cell is depolarizing it is becoming more positive. So, a positive depolartization toward a positive lead will inscribe a POSITIVE deflection on the EKG paper.

Remember. When the cell is depolarizing it is becoming more positive. So, a positive depolartization toward a Negative lead will inscribe a NEGATIVE deflection on the EKG paper.

A depolarization that is perfectly PERPENDICULAR to the lead will incribe an isoelectric (i.e. baseline) on the EKG. However, this is rare, and most of the time the EKG will be biphasic (but very close to isoelectric).