Electro(patho)physiology Generation of action potential and its conduction in heart Abnormalities of the heart rhythm Cardiac output – CO = SV x f Resting membrane potential – One ion • Nernst equation – Several ions • Goldmann equation • Determined by: – fixed intracellular anions – membrane permeability • i.e. density and channel gating – Na + /K + -ATP-ase Cardiac automacy • Due to physiologic instability of membrane potential of P cells of the SA node time (s) 0 -40 -80 threshold potential time (s) 0 -50 -90 absolute refractory phase cell of the SA node contractile myocyte cationt channels (mainly Na + ) Ca 2+ channels relative refractory phase 250ms resting potential action potential Na + channels Ca 2+ channels K + channels Na+/K+ ATP-ase Na+/K+ ATP-ase Temporal and spatial coordination of potential changes Conductory system of the heart • SA node – internodal atrial tracts • Bachmann, Thorel, Wenckebach • Atrioventricular (AV) junction – AV node – AV bundle • Right and left bundle branch • anterior and posterior fasciculus • Pukrynje fibres
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Generation of action potential and its conduction in heart ... · • early after-depolarisation – manifests as a ventricular tachyarrhythmia • late after-depolarisation – manifests
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Electro(patho)physiologyGeneration of action potential and
its conduction in heart
Abnormalities of the heart rhythm
Cardiac output – CO = SV x f
Resting membrane potential
– One ion
• Nernst equation
– Several ions
• Goldmann equation
• Determined by:
– fixed intracellular anions
– membranepermeability
• i.e. density and channel gating
– Na+/K+-ATP-ase
Cardiac automacy
• Due to physiologicinstability of membranepotential of P cells of the SA node
time (s)
0
-40
-80
threshold potential
time (s)
0
-50
-90
absolute refractory phase
cell of the SA node
contractile myocyte
cationtchannels
(mainly Na+)
Ca2+ channels
relative refractory phase
250ms
resting potential
action potential
Na+ channels
Ca2+
channels
K+ channels
Na+/K+ ATP-ase
Na+/K+ ATP-ase
Temporal and spatial coordination of potential changes
Conductory system of the heart • SA node
– internodal atrialtracts• Bachmann, Thorel,
Wenckebach
• Atrioventricular (AV)junction– AV node
– AV bundle
• Right and left bundle branch
• anterior and posterior fasciculus
• Pukrynje fibres
Connection between cardiocytes
• gap junctions
– intercellular channels (d=1.5 - 2nm)
– transport of ions and small molecules (<1kDa)
– 4 – 6 connexinsubunits
Dominant and auxiliary pacemakers
Excitation – contractioncoupling
Excitation – contractioncoupling
Ion channels
• Voltage gated
–Na+ channels
–K+ channels (Kv, Kir)
–T-Ca2+ channels, L-Ca2+ channels (DHP)
• Ligand gated (G-protein)
–K+ channel sensitive to acetylcholine
–K+ channel sensitive to adenosine
• Ligand gated (without G-protein)
–K+ channel sensitive to ATP
• Mechanically gated (stretch)
Contractile apparatus
Classification of heart rhythm abnormalities = arrhythmias• (1) according to effect