Week 1 Flashcards
Polarization / Depolarization
The inside of a cardiac cell being kept negatively charged / cardiac cells losing their internal negative charge
Pacemaker Cells
Small cells that depolarize spontaneously over and over again at a particular rate; serve as the source of a wave of depolarization that initiates one complete cycle of cardiac contraction and relaxation
SA Node
Cluster of pacemaker cells that are located up in the right atrium
What type of cells constitute the majority of heart tissue?
Myocardial cells; responsible for heavy labor of repeatedly contracting and relaxing & delivering blood to body
3 Characteristics of an EKG wave:
Duration (mili seconds), Amplitude (mV), Configuration (shape)
Horizontal axis / what does 1 small square measure / 1 large square?
Time / .04 seconds / .2 seconds
Vertical Axis / Small Square / Large Square
Voltage / .1 mV / .5 mV
Delay after the P-wave is caused by / why is it necessary?
Electric activity is held up at AV node / necessary to allow right atrium to finish contracting before the ventricles contract
Pathway of electricity through the heart
SA node in R atrium –> AV node –> Bundle of HIS –> R and L bundle branches –> Terminal Purkinje Fibers
Q-Wave:
First downward deflection = depolarization of the septum
R-wave:
First upward deflection; 2nd upward deflection = R prime
S-wave:
1st downward deflection after an upward deflection
Describe Leads 1-3:
1: L arm pos, R arm neg, 0 degree angle. 2: Legs pos, R arm neg, 60 degrees. 3: L arm neg, legs pos, 120 degrees.
Describe the Augmented Leads:
AVL: L arm pos, all other limbs neg, -30. AVR: R arm pos, all other limbs neg, -150. AVF: legs neg, all other limbs pos, 90.
Best leads for viewing the inferior surface of the heart?
2, 3, AVF
Where are the 6 precordial leads placed?
(1) 4th IC space R of sternum, (2) 4th IC space L of sternum, (3), btw 2 & 4, (4) 5th IC space MC line, (5) btw 4 & 6, (6) 5th IC space MA line
Length of PR Interval:
.12 sec - .2 seconds (3-5mm)
Length of QRS Complex:
.06-.1 seconds
Contractility:
Ability of cardiac muscle to convert electrical signal into mechanical action
Automaticity:
Ability of cardiac cell to depolarize spontaneously
Excitability:
Ability of cardiac muscle to respond to stimuli and generate Action Potential
Fast Response Action Potentials - found in what cells / caused by influx of ______________?
Cardiac cells that are NOT pacemaker cells (myocytes, Purkinje fibers, bundle branches, etc) / Caused by influx of Sodium
Slow Response Action Potentials - found in what cells / caused by influx of __________?
Cardiac cells that are pacemaker cells (cells in SA and AV node) / Caused by influx of Calcium
