Heart Electrophysiology Flashcards
What are intercalated disks composed of
desmosomes and gap junctions
What does electrical activity spread through
gap junctions
Where are gap junctions found
nodal cells, conducting cells and myocytes
Where is electrical activity initiated
sino atrial node
What is the function of sino atrial node
determine heart rate
Where is the sino atrial node located
right side, junction between superior vena cava and right atrium
Describe the pathway of electrical signals in the heart
right then left atrium, through the inter atrial tract to the AV node, down the bundle of His, into purkinje fibres to ventricular muscle cells
What does the spread of electrical activity occur through from right to left side
Bachmann’s bundle
Which atrium contracts fractionally faster than the other one
right atrium
What are the three subzones of the AV node
atrial nodal, nodal, nodal ventricular
Why does the electrical signal slow down at the AV node
generate an atrio ventricular delay - allows atria to finish contracting
What is the function of AV refractoriness
prevent excess ventricular contraction
What is the relationship between heart rate and AV refractoriness
inverse relationship
What is the effect of increased HR on AV node firing ability
as HR increases, ability of AV node to fire decreases
What is the effect of increased HR on AV refractoriness
increased HR increases AV refractoriness
Describe the pathway of electrical activitiy
specific pathway
What does the specific pathway of electrical activity create
spiral contraction - torsion
Where does sub nodal contraction occur
bundle of His, Purkinje fibres and ventricular muscle
Why is the twisting movement of heart contraction important
important for effective removal of blood
What are the types of cardiac action potentials
nodal and contractile
What exhibits nodal action potentials
SA node and AV node
What exhibits contractile action potentials
atrial muscle, purkinje fibres and ventricular muscle
TRUE or FALSE - all cardiac action potentials are different from nerve potentials
true
What is characteristic about contractile action potentials
plateau phase at the peak of the action potential
What cells do not have a resting membrane potential
pace maker cells
What do pacemaker cells show
automaticity and rhythmicity
Describe the membrane potential of pacemaker cells
resting membrane potential peaks at -60mV but instantly starts a slow depolarisation, then steep AP phase
What causes pacemaker potential phase
reduction in potassium permeability
What is the funny current mediated by
hyper polarisation induced channel HCN4
What is slow depolarisation of pacemakers caused by
reduction in permeability to potassium
What causes pacemaker action potential depolarisation
voltage gated calcium channels
Which node is the more dominant
sino atrial node
What is the effect of the sympathetic nervous system on pacemaker cells
increases prepotential slope, increases firing rate
What is the effect of the parasympathetic system on pacemaker cells
hyperpolarisation, decreased pre potential slope
Describe calcium release in the nodal cells
spontaneous release through ryanodine receptors
What can calcium release cause in pacemaker cells
membrane depolarisation
What is depolarisation mediated by in cardiac muscle
voltage gated sodium channels
What is the plateau phase mediated by in cardiac muscle
voltage gated calcium channels
What is the repolarisation phase mediated by in cardiac muscle
voltage gated potassium channels
What is the sodium channel in the heart and AV myocytes
Nav1.5
What is the main calcium channel in the heart
Cav1.2 (L-type calcium channel)
What two channels mediate repolarisation in heart cells
HERG and KcLQT1
