Flashcards in Lectures for exam 1 Deck (90):
Poduce impulse without stimulation
Which cells exhibit Automaticity?
Pacemaker cells in SA node
Ability to respond to an electrical stimulus
Which cells exhibit Excitability?
Electrical conduction cells (myocardial cells)
Ability to transmit electrical signal from cell to cell
Which cells exhibit Conductivity?
Electrical conducting cells (myocardial cells)
3 cells of the heart?
1. Electrical conducting cells
2. Myocardial cells
3. Pacemaker cells
Which cells are the hard wiring of the heart?
Electrical conducting cells
Which cells are the contractile machinery of the heart?
Which cells are the muscle cells of the atria and ventricles?
Which cells are able to depolarize spontaneously and are the normal electrical power source?
What determines the rate of the pacemaker cells? (2 things)
1. Innate electrical characteristics of cells
2. External neurochemical input
Examples of electrical conducting cells?
AV Node, His bubdle, LBB, RBB, Ant and Post Fascicles, Purkinge fibers
Pathway of electricity in the heart to myocardial cells?
Pacemaker->Contracting pathway->myocardial cells
What is the Cardiomyocyte Action Potential responsible for initiating?
Initiating each cardiac contraction
What initiates cardiac contraction?
Cardiomyocyte Action Potential
What are the 2 types of Cardiomyocyte Action Potential?
Spontaneous and Non-spontaneous
Are pacemaker cells in the SA node spontaneous or non-spontaneous Cardiomyocyte Action Potential?
Are cardiac muscle cells spontaneous or non-spontaneous Cardiomyocyte Action Potential?
What chemicals increases rate of pacemaker cell discharge causing increased heart rate?
Catecholamines (Epi and Norepi)
What chemical causes the decrease of pacemaker cell discharge thus slowing the heart rate?
What releases Acetylcholine?
Released during vagal stimulation
What causes myocardial cells to contract?
Depolarization which releases calcium from sacroplasmic reticulum
What type of coupling do myocardial cells exhibit?
What muscle components do myocardial cells contain?
Actin and myosin
What does the EKG waveform primarily reflect?
Electrical activity of myocardial cells
What are the 3 main characteristics of the EKG waveform?
1. Duration in ms
2. Amplitude in mV
When does ventricular excitation begin?
Begins at atrial relaxation
Time duration of small square on EKG paper?
Time duration of large square on EKG paper?
How many small squares make up a large square on EKG paper?
5 small squares long and high
How many precordial leads are there?
Precordial leads aka?
Chest leads or V leads
Which are the six precordial leads?
How many Limb Leads are there?
What are the three Limb Leads called?
Lead 1 degree? Which arm positive and negative?
0º. Left arm positive, right arm negative.
Lead 2 degree? What is positive and which arm negative?
60º. Leg positive, right arm negative.
Lead 3 degree? What is positive and which arm negative?
120º. Leg positive, left arm negative
What are the 3 augmented limb leads?
aVL degree? Positive and negative?
-30º. Left arm positive, other limbs negative.
aVR degree? Positive and negative?
-150º. Right arm positive, other limbs negative.
aVF degree? Positive and negative?
+90º. Leg positive, other limbs negative.
Which are the 3 anterior leads?
Which are the 3 inferior leads?
II, III, aVF
Which are the 2 Right Ventricular leads?
Which are the 4 Left Lateral leads?
I, aVL, V5, V6
Where does Atrial Excitation begin and complete?
What depolarized in the P-Wave?
Both atria. RA then LA.
Normal P-wave amplitude?
Normal P-wave duration?
Which lead does P-wave have negative deflection
Where does P-wave have biphasic deflection? (hint: 2)
P-Wave deflection variable/unpredictable in which 3?
V2, V3, V4
P-wave amplitude in Right Atrial Enlargement?
>2.5mm. Normal duration.
What will V1 show in Right Atrial Enlargement?
Taller initial component in biphasic P-wave
Amplitude of P-wave in Left Atrial Enlargement?
Normal or increased
P-wave in Left Atrial Enlargement?
Wide, often notched
V1 P-wave in Left Atrial Enlargement?
Wide biphasic wave
PR interval is from start of what in atria to start of what in ventricles?
Time from start of atrial depolarization to start of ventricular depolarization
Normal time of PR Interval?
0.12 to 0.2 seconds (up to one big box)
What can it means if PR Inteval is more than one big box?
PR Segment is from end of what in atria to beginning of what in ventricles?
Time from end of atrial depolarization to beginning of ventricular depolarization
What does the Q-wave reflect?
Left to right septal depolarization
What is a pathological Q Wave due to?
Irreversible myocardial damage.
When does a pathological Q Wave occur?
Hours to days after an MI
Duration of pathological Q Wave?
Depth of pathological Q Wave?
≥1/3 height of R wave
Which lead’s negative deflected QRS complex is not a pathological Q Wave?
What depolarizes in QRS-complex?
Remainder of ventricles depolarize (started with PR Segment)
Average vctor of QRS-complex correct flow?
0º to 90º
Which 2 leads have deep negatively deflected S-waves?
V1 and V2
What is R-Wave Progression?
Pattern of progressively increasing R-wave amplitude from right to left in V1-V6
Which lead do the R-Wave Progression occur in?
What is a normal QRS-interval (duration)?
Narrow is normal! 0.06-0.1sec
QRS-interval not more than how many small boxes?
Duration of a wide QRS-interval?
2 causes a wide QRS-interval?
1. Impulse generated in ventricle
2. Abberant pathway through ventricle
ST-segment time from end of what to start of what?
Time from end of ventricular depolarization to start of ventricular repolarization
What can you tell from ST-segment?
Active cardiac ischemia or infarction (STEMI)
STEMI height in limb leads (I, II, III)?
STEMI height in precordial leads (V1-V6)?
Tombstone or frowning face appearance?
STEMI in precordial leads (V1-V6)
ST depression is a sign of what?
T-waves represent what?
QT-interval is beginning of what to end of what?
Beginning of ventricular depolarization to end of ventricular repolarization
QT-interval is inversely proportial to what?
What is a normal precent of the QT-interval?
Normal QT-interval is where between two QRS complexes?