Electriophysiology Flashcards
P wave
atria depolarization
both atria at the same time through bachmann bundle
QRS complex
ventricles depolarization
S wave
Depolarization wave go up the ventricles
R wave
Depolarization wave go to purkinje fibers. Left side is strongest because myocardium larger
Q wave
Depolarization wave go down the bundle of his, Left & Right bundle and myocytes of septum
left-to-right depolarisation of the interventricular septum
Action potential pacemaker cells
Phase 4 : HCN/fuzzy channels open -> Na+(Sodium)-> enter -> slow depolarization until treshold potential
Phase 0: voltage gate Ca2+(calcium) channels open -> Ca2+ enter -> rapid depolarization
Phase 3: K+(potassium) channels open -> K+ out of the cell -> K+ channels > Na2+ channels -> cell get inside more negative -> repolarization
Action potential for nonpacemaker cells
Phase 4: Resting membrane potential phase
Gap junctions -> Ca2+(Calcium) enter -> treshold potential. all K+ channels are closed.
Phase 0: -> voltage gated Na+ (sodium) channels open -> Na+ enter->depolarization
Phase 1: initial repolarization. voltage gate K+(potassium) channels open -> K+ out of cell
Na+ channels close -> more + out -> repolarization
Phase 2: Ca2+ channels close -> only K+ out of cell -> repolarization -> hyperpolarization
Protein transport K+ into and Ca2+ out of the cell to restore resting concentrations.
ECG
See the depolarization wave
Amplitude changes with how much myocardium there is
If the depolarization wave is diagonal to the positive lead, vector and see magnitude towards the electrode.
if perpendicular to positive lead: straight line
Atrial repolarization is not seen on ECG
Depolarization
wave of positive charge inside from negative lead to positive lead.
=> dipole towards positive
negative charges outside
This gives a positive curve
Happens all at once because fibers fire quickly
Contraction
Depolarization wave travels by ions (Na+ and Ca2+) going through gap junctions to reach next myocytes -> voltage gated sodium channels open -> Na+ enter into the cell -> action potential
Repolarization
wave of negative charge inside from negative lead to positive lead.
=> dipole towards negative
negative charges outside
This gives a negative curve
gradual and different times for myocytes
Relaxation
Chest leads
V1-V6 measure the electrical field towards them (+)
go from right parasternal to left axillary
transverse plane
v1,v2 mostly negative ECG, interventricular septum
v3,v4, anterior wall
v5,v6 mostly positive ECG, lateral leads, left circumflex artery
AVR, AVL, AVF
augmented
unipolar: positive pole
AVR: right arm, -150°
AVL: left arm, lateral lead, left circumflex artery, -30°
AVF: leg, interior lead: coronary artery, 90°
Lead I,II,III
makes a triangle with AVR, AVL, AVF
bipolar leads
Lead I: - aVR to aVL +, left circumflex artery
Lead 2: - aVL to aVF +, right coronary artery
Lead 3: - aVR to aVF +, right coronary artery
12 lead ECG
aVR, aVL, aVF, Lead I,II,III and v1-6
movement of + charges on the outside of heart cells
Sinus rythm
Sinoatrial node (SA) node made of pacemaker cells-> pacemaker cell depolarize -> spread
Conductivity
myocytes slower than pacemaler cells
Electric conduction
P Q R S T
SA node fires, both atria depolarize through the bachmann bundle, conduction from SA node to AV node through internodal tracts
travels through bundle of his, left/right bundle and myocytes, then go to purkinje fibers and up the ventricles
PR interval
SA node to AV node, time between atrial and ventricular contraction
straight line between P and Q wave
ST
no electrical activity at the end of depolarization until repolarization : J point
T
ventricles repolarize (-) QT is the ventricular systole
Inflection
positive inflection if depolarization towards + lead or repolarization away of + lead
myocytes
muscular wall, receive electricity from pacemakers cell, slower conductivity
contractile conduct
pacemakers cell
1% of heart cells
SA, AV node, atrial internodal tracts, (bachmann bundle), bundle of his, left/right bundle, purkinje fibers
autorithmic: continuously generate Action Potentials
Fast conduction and autorythmic if not conducting
1 fire in SA node -> Action Potential -> Heart Beat Conduction
SA node has higher firing rate, if not done by SA node: ectopic focus
membrane potential
difference in charge inside/outside
negative: more + outside than inside
potential changes when Ca 2+, Na2+ go through the permeable membrane
membrane potential down during depolarization
AV node
atrioventricular node has a slower condution: small diameter and slow ion channels.
Delay allow ventricles to fill before they contract
Pump
calcium pump
sodium-potassium pump
Protein transport K+ into cell and Ca2+ out of cell to restore the concentrations
Conduction velocity
depolarization wave travels to all relevant parts of the heart in 220ms
More sodium (Na) -> speed depolarization increase
Less gap junctions -> speed depolarization decrease
Bundle of his and purkinje fibers fastest then ventricles and atria and last AV Node
Excitability
inward current needed for depolarization
highly excitable: sodium (Na) channels open
inactive channels then need more ions from gap junctions
hyperexcitable: supranormal period
Absolute refractory period
unexcitable, AP cannot be activated, Na+ channels closed until hyperpolarization
Effective refractory period
some sodium (Na+) channels start to recover but still not possible to have AP
Relative refractory period
hyperpolarization, action potential can occur but with a big stimulus
