Cardiac APs Flashcards Preview

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Flashcards in Cardiac APs Deck (6):
1

Significance of IK1 Channels:

- These create the INWARD rectifier current.
• Does not "gate" like other channels:
- passes + charge more easily into the cell than out of the cell.
• Functions to maintain resting membrane potential by making minor changes in potential
○ Either influx or efflux of potassium

2

Significance of If currents:

• HCN tetramer
• Funny current: Considered "funny" because it is turned off at depolarized potentials and on at hyperpolarized potentials
○ Ability to be activated at hyperpolarization is important in pacemaker cells w/o neuronal stimulus b/c it allows AP firing without stimulus from innervation
• Permeable to both Na and K

3

"Overdrive suppression"

other cells have pacemaker activity and can become pacemakers, but that SA nodal firing suppresses this activity. Other sites are:
• Can be located in:
1. AV node and purkinje fibers
2. Ectopic pacemaker cells:

4

Why is the SA node the dominant pacemaker activity?

it has the highest intrinsic rate of automaticity

5

Ectopic pacemaker cells:

Can be cells that display automaticity (like SA node) because of hypoxic conditions

6

During the refractory periods, there is still inactivation of what current?

INa
It is not until there is complete removal of inactivation of INa and deactivation of IKr and IKs, that a normal action potential can be initiated.