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Host Defense Exam 2 (by Richie) > Lisps Review > Flashcards

Flashcards in Lisps Review Deck (13):
1

Ca channel blockers inhibit

L-type channels. This slows the upstroke of AP and the plateau. Thus it is responsible for conduction.

2

3 K+ channels in heart?

IK channel: phase 3 repolarization

ITO channel: phase 1 repolarization

IK1 channel: BACKGROUND CURRENT that determines RMP. This channel is not "on or off"...not voltage "gated", but voltage "dependent"...during depolarization free Mg2+ plugs K+ channel. This is why conduction decreases over depolarization. RESPONSIBLE FOR PLATEAU OF AP.

3

What does hyperkalemia do to Vg Na channels?

Reduces their rate of activation, slowing inward Na+ current. Promotes conduction block, and re-entry.

4

Triggered activity. 2 Types?

DAD: abnormal release of Ca from SR (overloaded, like in digitalis toxicity)...Ca/Na exchanger compensates by inward Na current, which promotes depolarization that can possibly hit threshold.

EAD - more serious. Long depolarization. EAD caused by long AP, which causes EAD (positive feedback). Acidosis or ischemia, or quinones, can increase length of AP.

5

Diastolic depolarization determines...

pacemaker rate. Only part of AP that has to do with rate. Has nothing to do with conduction.

6

Upstroke of AP determines...

conduction. Pertains to synchrony of cells contractions. Eg. QRS conduction

7

Refractory period determines...

duration of AP. Has nothing to do with conduction either.

8

Ventricular rate is determined by

AV node

9

2 things that can depolarize resting membrane potential

1. Ischemia/infarct (local K+ buildup)
2. Hyperkalemia

Both promote slurred QRS, and re-entry

10

Space constant is positively determined by

Size of cell and number of nexal connections (His-Purkinje has biggest space constant)

11

What determines shape of QRS

normal conduction through His-purkinje system

12

Autonomics effect sinus rhythm how?

Val Salva maneuver or cold water on face → high vagal stimulation → suppresses arrhythmia (eg. Wolf-Parkinson-White) → lowers O2 demand on heart

13

What does an L-type Ca blocker do to AV node?

Slows upstroke of AP, thus slower conduction.