The Basics Flashcards
What are the electrical power sources of the heart?
What are the hard wiring cells of the heart?
What are the contractile cells of the heart?
Pacemaker Cells
Electrical Conducting Cells
Myocardial Cells
One electrical cycle of depolarization and repolarization from a single cell gives an electrical tracing called?
An Action Potential
Resting membrane potential of the heart
-90mV
Normal rate of the SA node
60-100
It is the normal pacemaker cell of the heart
What allows the action potential to travel from the right atrium to the left atrium?
Bachman’s Bundle
What is the electrical pathway of the ventricles called?
Purkinje system
What ion is released intracellularly that causes contraction?
Calcium
EKG paper usually moves at _____
At this speed, each large square represents _____ seconds
25 mm/sec
0.2 seconds
In amplitude, one small square represents_____
and one large square represents_______
- 1mV
0. 5mV
If you reduce standardization by 1/2, the QRS complex_____
Shrinks (by 1/2)
The P wave shows
depolarization of the atria
The first part of the p wave represents____
right atrial depolarization
What causes the brief pause before the electrical signal is passed from the atria to the ventricles?
The AV node
Why is the pause created by the AV node important?
Allows the atria to finish contracting and empty their contents before ventricular contraction occurs
Vagal stimulation does what to current flowing through the AV node
Slows the current further
Flow of current through the Ventricles:
Right Side:
Bundle of His
Right Bundle Branch
Purkinje Fibers
Left Side: Bundle of His Left Bundle Branch Septal fascicle, Anterior fascicle, Posterior fascicle Purkinje Fibers
What does the QRS represent?
ventricular depolarization
What fascicle runs along the anterior wall of the left ventricle?
Anterior Fascicle
What fascicle depolarizes the IV septum in a left to right direction?
Septal fascicle
In the QRS complex:
First deflection downward=
First downward deflection following and upward deflection=
Q wave
S wave
In the QRS complex:
First upward deflection=
Second upward deflection=
R wave
R’ wave
If the entire QRS is solely one downward deflection, the wave is called
QS wave
The T wave represents
Ventricular repolarization
Straight line connecting 2 waves=
Segment
Straight line connecting 1 wave plus a straight line
Interval
PR Interval measures
start of atrial depolarization to start of ventricular depolarization
PR segment measures
end of atrial depol to start of ventricular depol
St segment measures
end of ventricular depol to start of ventricular repolarization
QT interval measures
beginning of ventricular depolarization to end of ventricular repolarization
A depolarization wave moving towards a positive electrode cause a ________ deflection
Positive
A depolarization wave moving away from a positive electrode causes a _________ deflection
Negative
A depolarization wave moving perpendicular to a positive electrode causes a _________ deflection
Biphasic Wave
A wave of repolarization moving towards a positive electrode causes a ________ deflection
Negative
The limb leads create what kind of plane?
Vertical Plane= Frontal Plane
The three standard limb leads are:
Bipolar
Lead I, Lead II, Lead III
Lead I angle of orientation is
The left arm is ____ and the right arm is ____
0 degrees
Left arm positive, right arm negative
Lead II angle of orientation is
+60
Lead III angle of orientation is
+120
Lead I + Lead III=
Lead II
The three augmented unipolar leads are
aVL, a VR, and aVF
Lead aVL angle of orientation is
-30
Lead aVR angle of orientation is
-150
Lead aVF angle of orientation is
+90
P wave voltage sum of
aVR + aVL + aVF=
0
Inferior Leads=
Lead II, III, and aVF
Left Lateral Leads=
Leads I, aVL
Right sided limb lead=
aVR
Precordial leads record forces moving____ & _____
anteriorly & posteriorly
In women what leads are placed under the breasts?
Leads V3 to V6
V1 is placed
V2 is placed
V3 is placed
in the 4th intercostal space to right of sternum
4th intercostal space to left of sternum
Between V2 and V4
V4 is placed
V5 is placed
V6 is placed
5th intercostal space, midclavicular line
Between V4 and V6
5th intercostal space in midaxillary line
What body surface should you never use to locate position of electrodes
nipples
The positive pole for each chest lead points
Anteriorly, toward the front of the chest
A wave of depolarization moving towards a positive limb lead creates an ______ deflection
Upward
Positive P waves are expected in leads
I, aVL, II, aVF
V5, V6
A biphasic p wave is expected in leads
Lead III
V1
Negative P waves are expected in leads
aVR
In any square the P wave amplitude is typically less than
.25mV or 2.5 small squares
Initial negative deflection of the Q wave may be seen in leads
I, aVL, V5, V6
Normal Q waves have an amplitude no greater than
.1mv
Large positive R waves may be seen in
left lateral and inferior leads
Transition zone or leads in which QRS complex goes from mostly negative to mostly positive is typically seen in
V3 or V4
QRS complex generally lasts
.06 to .1 seconds
ST segment is generally _______ in ____ leads
Horizontal or gently up slopping in all leads
Normal T wave is always negative in lead_____ but positive in lead_____
Negative in aVR
Positive in lead II
If the T wave is positive in any chest lead it must ________ or it is abnormal
remain positive in all the chest leads to the left of that lead
Normal T wave amplitude is
1/3 to 2/3 that of the corresponding R wave
In a normal QT interval the_____ is wider than the ____
T wave is wider than the QRS
