Electrophysiology of the Heart Flashcards
Na+ gradients
concentration - more outside the cell
electrical - more outside the cell
K+ gradients
concentration - more inside the cell
electrical - more outside the cell
Ca++ gradients
concentration - more outside the cell
electrical - more outside the cell
Cl- gradients
concentration - more outside the cell
electrical - more inside the cell
Protein- gradients
concentration - more inside the cell
electrical - more inside teh cell
Na+ permeability at rest
not permeable
Na/K ATPase is pumping it out of the cell
K+ permeability at rest
permable
Ca++ permeability at rest
not very permeable
concentration maintained by active sequestration into SR
Phase 0 permabilities
increased permeability to sodium
Phase 1 permabilities
decreased permeability to sodium
Phase 2 permeabilities
increased permeability to calcium
decreased permeability to K+
Phase 3 permeabilities
increased permeability to K+
decreased permeability to Ca++
When does Fast Na+/Ca++ channel open
Phase 0
When does slow Na+/Ca++ channel open
Phase 2
Effective refractory period
absolute refractory period, begins at upstroke of phase 0 and ends when Na+ channels are reset to resting potion in phase 3
Why can the heart not undergo tetany
because of the effective refractory period
Relative refractory period
begins where ERP ends. Ends when normal AP can be generated
Phase 0 of SA nodal pacemaker AP
upstroke/depolarization
Ca++ enters cell
Phase 3 of SA nodal pacemaker AP
repolarization
K+ exits cell
Phase 4 of SA nodal pacemaker of AP
slow depolarization/pre potential
Na+ enters cell via funny current
Example of positive Chronotroph
norepinephrine, epinephrine, isoproterenol
What does positive chronotroph do
increases permeability of nodal cells to N+ and Ca++
increases HR
What does postiive chronotroph do to slope
increased slope of phase 4
Example of negative chronotroph
acetylcholine
