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31 Cards in this Set
- Front
- Back
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What feature allows Purkinjee fibers to be Fast cells with automaticity
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They have Special Na channels that act in opposite manner of Ca+---they will OPEN when cell repolarizes to phase 4. Very slow, SA and AV will reset this first
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Describe how Sympathetic Stim. affects the depolariztion rate during Phase 4 and the SA node rate.
What type of trophic effect is this? |
It Increases the depol rate & increases pacemaker/SA rate
--Positive Chronotrophic Effect |
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Which Receptors, NTs and Ions are important for Positive Chronotrophic effect
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Beta 1 Receptors, Norepi
& Ca++ (increased G) |
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Describe how PARAsympathetic Stim. affects the depolariztion rate during Phase 4 and the SA node rate.
What type of trophic effect is this? |
Para increases the Membrane Potential (makes more Neg) and Decreases Depol Rate of Phase 4
Neg Chronotrophic- |
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Which Receptors, NTs and Ions are important for Negative Chronotrophic effect
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AcetylCholine, Muscarinic Receptors and K+ (increased G)
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Term for an AP that never meets tissue in a refractory state OR tissue that has Just exited its refractory period allowing AP propogation
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ReEntry
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3 Reasons for why it takes nearly 1/10 of second (relatively long) for AP to pass through the AV node, a small length of tissue
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--Small size of cells
--Low amplitude of AP --Slow rate of depolarization during excitation. ParaS. exacerbates this, SYMp relieves. |
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In contractile myocytes, during what phase does Ca++ enter cell from T-Tubule
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during the AP plateau, Phase 2.
This is phase on AP where Ca perm is High (keeps cell positive) |
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Describe a Positive Ionotrophic effect
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When Symp. Stim. causes greater force of contraction by Increasing Ca++ Intracellularly.
--it also Increases Rate of Ca reuptake causing phase 2 to shorten/ shortens systole |
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Describe Parasympathetic Stim on Contractile Myocytes
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Weak effect. Unlike the strong/positive ionotrophic effect from Symp Stim.
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Cardiac Glycosides have what effect on Intracellular Ca++?
Mechanism? |
They increase it/ increasing force of contraction.
-Inhibit Na+/K+ pump. Na buids up inside=easier to depol=easier to contract |
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Describe the more clinically relevant effect of HYPOkalemia?
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Na/K pump affected. Though Low K+ inside = more neg insider (hyperpolarized). however, Greater effect is Na buildup inside, which leads to depol and arrhythmias
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Hyperkalemia has what effect on AP
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Slows AP and alters Phase 3--due to reduced AMPLITUDE
--dec. amp is conductance factor for slowing an AP |
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What leads to decreased contractility? Hypo or Hypercalcemia?
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Hypo = dec contractility
Hyper = Inc contractility |
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P-wave includes?
Duration? |
SA AP spreading Right to Left through atria
2 sq. / .08secs--????---less than prolly |
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QRS includes? Directionality?
Q=?, R=?, S=? Duration? |
AP spreading through Ventricles from Right to Left and Apex to Base. Q is first neg. R is first pos. S is first neg AFTER a positive
<3 sq. < .12s --Q wave is seldom signif. Presence of all 3 is seldom |
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T-wave includes? Directionality
Duration? |
Repolarization spreading through Ventricles. Upper left to Lower Right Ventricles.
Not specified. |
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5 Phases of Fast Cardiac AP:
-4 is ?? caused by High ?? -0 is ?? caused by High ?? -1 is ?? caused by LOW ?? and High ?? |
-4-resting, High G K+
-0-rapid depol, High G Na+ -1-inital repol, Low G Na+ & High G K+ (normal K channel) |
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5 Phases of Fast Cardiac AP:
-2 is ?? caused by Low ?? & High ?? -3- is ?? caused by Low ?? & High ?? |
-2-plateau Low G K+, High G Ca++
-3-Repol, Low G Ca++ (caused by..) High G K+ (special K--causative of Ca closure) |
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Which ANS stimulation lengthens phase 4? Which shortens it.
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Para lengthens phase 4. Sypm shortens it and inc. contractility
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What is extracellular resting potential?
At phase 2/Plateau? |
+90 mV (b/c its -90 just inside mem)
-15 mV (b/c AP send is from -90inside to +15inside) |
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What EKG period shows AV node delay of AP?
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PR Interval
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What EKG part displays the AP Phase 2 delay of repolarization in ventricles?
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The ST Segment
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Describe the QT Interval?
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begin of Ventricular Depol to end of Repol.
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What are 4 types of Leads?
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-Standard Limb leads 1-3
-Augmented Leads aVR, aVL & avF -Chest Leads V1 - V6 -Ground/ RL ---Standard Leads 1 (RA->LA), 2 (RA ->down->LL), 3 (LA ->down->LL) |
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Which 3 form Einthovens Triangle
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tandard Leads 1 (RA->LA) through heart
2 (RA ->down->LL) up R to low L 3 (LA ->down->LL) up L to low L |
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aVF points from? to ?
aVL points from? to ? aVR points from? to ? |
neck directly down
lower Right to Left Shoulder lower Left to RIght Shoulder --think about vector pointing to Last Letter, F=feet |
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Chest leads give closer look from ? to ? on chest
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from right Atrium (where it is placed) and around to lateral view of ventricles
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Duration of atrial Depol + AV delay is? Normal Duration?
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PR interval (though ends before Q of QRS even starts)
-3-4 sq. .12 to .16 secs |
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Describe QT interval?
Duration at 60 beats/min Changes if <60? >60? |
Begin of QRS to end of T/ depol to repol of ventricles
--12 sq or .48 secs at 60/min --<60 is longer than .48 --->60/higher rate it is shorter than .48s |
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Long QT interval is sign for sudden cardiac probs due to abnormality with what channel
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The Special K channels
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