Lab 6 Flashcards
Define Electrocardiogram (ECG/EKG)
a non-invasive tool for evaluating the electrical events of the heart as well as beating rate and rythym
What does an ECG do?
measures the voltage difference between two points on the surface of the body caused by differences in voltage outside a large number of cardiac cells
Describe the two phases of the cardiac cycle
Systole: the period of ventricular contraction and blood ejection
Diastole: the period of ventricular relaxation and blood filling
Why is the heart considered an electrical syncytium?
cells that are interconnected by gap junctions which are synchronized electrically in an action potential
Where does initial depolarization occur?
SA Node
What do the SA node, AV node, and Purkinje fibers all have in common?
they do not contract, but they spread electrical signals
What do conducting system cells do?
help spread an action potential throughout the heart
What information is received from an ECG?
-monitors the spread of net vector
-records the net currents that are generated in the ECF by membrane potential changes occurring in the cardiac cells at 2 different points of the body
-1 completing tracing = 1 heartbeat
What were we doing in this lab?
observing and analyzing tracings from the standard 3-limb lead
What is the triangle of leads called?
Eindhoven’s triangle
What is the main vector in the triangle called?
net depolarization vector
If the net depolarization vector spreads towards the recording electrode, the defection will be…
positive
If the net depolarization vector spreads away from the recording electrode, the deflection will be…
negative
How are the deflections of depolarization and repolarization related?
they are opposite
What does the net vector spread being parallel to a lead lead to?
high amplitude in deflection
