Lecture 12: Multicellular Electrophysiology Flashcards
What does anisotropy mean in terms of cardiac cells?
The uneven spread of conduction velocity. Signals are transmitted much faster longitudinally than transversely in cardiac cells therefore the signal spreads outwardly in an oval shape as oppose to circularly.
How do typical neuronal and cardiac action potentials differ?
Nerve cells have a very rapid repolarisation (within a few ms) whilst cardiac cells have a prolonged depolarised phase (>100ms).
Does adult cardiac cell size stay constant across species?
Yes. No matter the size of the overall heart, the cell sizes are the same.
Do myocytes (cardiac cells) have more gap junctions longitudinally or transversely? Or the same amount for both?
More gap junctions longitudinally.
Is the axoplasm of a neuron high resistance or low resistance?
Low resistance.
Are gap junctions in myocytes high resistance or low resistance pathways?
Low resistance pathways.
Between myocytes, do action potentials travel from source cell to sink cell or sink cell to source cell?
Source cell to sink cell.
What does isotropic conduction mean?
Equal velocity in all directions.
What does anisotropic conduction mean?
Unequal velocities.
What two main things affect conduction velocity?
Cell to cell coupling and cell excitability.
What effect does high [Ca2+]i have on gap junctions?
It reduces cell to cell coupling.
Does a high or low pH reduce cell to cell coupling?
Low pH. Acidosis reduces coupling.
Dephosphorylation reduced coupling stems from what?
An ischaemic environment - not enough oxygen.
