Electrophysiology Flashcards
(33 cards)
Depolarization
Stimulates contraction
Repolarization
Resting cell, recovery from depolarization
Sodium (Na+) electrolyte roll in cardiac function
Flows into cell to initiate depolarization
Potassium (K+) electrolyte roll in cardiac function
Flows out of cell to initiate repolarization
Calcium (Ca++) electrolyte roll in cardiac function
Moves slowly into the cell, depolarization of pacemakers, maintains depolarization and myocardial contractility
Magnesium (Mg++) electrolyte roll in cardiac function
Stabilizes cell (works with K+), opposes Ca++
Hypercalcemia
High Ca++
High contractility
Hypocalcemia
Low Ca++
Low contractility
High myocardial irritability
Hypermagnesemia
High Mg++
High myocardial irritability
Hypagnesemia
Low Mg++
Decreased conduction
Hyperkalemia
High K+
High myocardial irritability
Hypokalemia
Low K+
Decreased automaticity/conduction
Cardiac Action Potential Phase 0
Cell depolarizes & begins to contract
Cells receive impulse
Na+ enters cell (positive change in TMP to meet threshold of -70 mV)
More sodium rapidly shoots up to +30 mV
Calcium start to enter slowly
QRS complex (really RQ segment)
Cardiac Action Potential Phase 1
Repolarization starts
Inward Na+ channels close
Negative chloride ions enter cell
Outward K+ channels open briefly (slight decrease in TMP, negative charge)
QS segment
Cardiac Action Potential Phase 2
Plateau phase (longest phase)
Na+ & Ca++ slowly enters cell while K+ flows out of cell (prolongs depolarization, creating plateau
Ends when outward flow of K+ exceeds Na+ & Ca++
ST segment
Cardiac Action Potential Phase 3
Final phase
Slowly Ca++/Na+ channels close
K+ rapidly leaves cell (causing TMP to drop and go negative)
T wave
Cardiac Action Potential Phase 4
Resting phase
Membrane potential of -90 mV
Transmembrane potential (TMP)
Change in the charge of a myocardial cell (-90 mV at rest)
Absolute refractory period (ARP)
Cardiac cells are unable to respond to any stimulus
Phase 0-3 of cardiac action potential
“If you flush a toilet, it needs time to refill”
Relative refractory period (RRP)
Enough cells have repolarized sufficiently to depolarize again
Mid phase 3 to beginning of phase 4
Time AV node delays pulse
0.12 seconds
Allows atria to empty blood into ventricles
AV junction includes:
AV node, surrounding tissue, non-branching portion of bundle of His
Time for pulse to spread across ventricles?
0.08 seconds
Ischemia definition
Tissue injury caused by hypoxia
