Intro to Electrophysiology Flashcards
What cardiac structure supports valves, separates atria and ventricles and electrically insulates atria from ventricles (electrical impulses must travel through conduction pathways)?
Cardiac skeleton
BP = __ x __ ?
BP = CO x PVR
The SNS acts via beta receptors to have what type of effects?
Cardioaccelerator effects
When is the SNS activated by the cardioregulatory center to release NE/ Epi, increase HR and contractility, constrict peripheral blood vessels, and increase CO and BP?
BP too low
The PNS acts via the vagus nerve to have what type of effects?
Cardioinhibitory effects
When is the PNS activated by the cardioregulatory center to release ACh, decrease HR and decrease BP?
BP too high
What type of cells are contractile cells?
Myocardial cells
What myocardial cell structure permits conduction of impulses longitudinally from one cell to the next?
Gap junctions in intercalated disks (connection point)
What myocardial cell strucutre surrounds the cardiomyocyte, preventing lateral signal transduction?
Sarcolemma
Myocardial cells contract as a unit and are held together by what?
Desmosomes
What are the 4 key properties of myocardial cells?
Automaticity, excitability, conductivity, contractility
What myocardial cell property is defined as the ability of certain cells to produce an electrical impulse without outside nerve stimulation?
Automaticity
What myocardial cell property is defined as the ability to respond to an electrical stimulus?
Excitability
What myocardial cell property is defined as the ability to transmit an electrical stimulus from cell to cell?
Conducivity
What myocardial cell property is defined as the ability to contract when electrically stimulated?
Contractility
What state of myocardial cells consists of negatively charged ions insie and positively charged ions outside?
Polarized state (resting state)
The difference in charges in the resting state of a myocardial cell results in what?
RMP (no net ion flow)
During an action potential, what ion movement results in depolarization?
Na+ quickly into cell and Ca slow (leads to positive charge inside cell)
During an action potential, what ion movement results in repolarization?
Na, Ca, K out of cell
Following depolarization, temporary resistance to further depolarization is defined as what?
Absolute refractory period
What keeps the depolarization wave moving forward and prevents spasms of continued contraction in one area?
Absolute refractory period
Period of time duing the late phase of repolarization in which only a strong electrical stimulus will cause depolarization is defined as what?
Relative refractory period
What type of cells have the ability to spontaneously generate an impulse (depolarize) at a certain rate?
Pacemaker cells
What is the pathway of conduction in the heart? (5)
SA node → AV node → bundle of His → R&L bundle branches → purkinje fibers
What is the primary pacemaker?
SA node
What is the intrinsic rate of the SA node and what ion drives it?
60-100 bpm, Na driven
What heart structure is a pathway for impulses to reach ventricles and slows the signal to allow atria to contract and empty as much blood as possible into the ventricles for stronger contraction and improved CO?
AV node
What is the intrinsic rate of the AV node and what ion drives it?
40-60bpm, Ca driven
What structures are located on either side of the IV septum?
R and L bundle branches
Left bundle branches split into what?
Ant and post fascicles
What heart structures are the terminal branches of the R and L bundle branches that spread throughout the myocardium?
Purkinje fibers
What is the intrinsic rate of the Purkinje fibers?
20-40bpm
What type of cells carry electrical impulses to appropriate regions of the heart?
Electrical conducting cells
Which leads are bipolar?
Limb leads I, II, III
Unipolar leads consist of what?
Only positive electrode + reference point
Which leads are unipolar?
Chest/ precordial leads (V1-V6), augmented limb leads
Which leads provide frontal plane views? Horizontal plane views?
- Limb leads = frontal plane views = einthoven’s triangle (leads I, II, III, aVR, aVL, aVF)
- Chest (precordial) leads = horizontal plane views (leads V1-V6)
What is the difference between vectors and axis?
Vectors = many small electrical currents in various directions, overall direction of sum of vectors = axis
Movement towards (+) electrode produces what?
Mark above baseline
Movement towards (-) electrode (or away from (+)) produces what?
Mark below baseline
Movement perpendicular to (+) electrode produces what?
Biphasic waveform
What ECG element represents atrial depolarization?
P wave
What ECG element represents ventricular depolarization?
QRS wave
(atrial repolarization hidden in QRS wave)
What ECG element represents ventricular repolarization?
T wave
