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Cardio > Lecture #3 > Flashcards

Lecture #3 Flashcards

1
Q

Purpose of Goldman-Hodgkin-Katz equation?

A

Calculate membrane potential

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2
Q

What is the Goldman-Hodgkin-Katz equation at body temperature?

A

E= (61.5) log10 [(Px(Xout) + …..)/(Px(Xin))]

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3
Q

What is the Nernst equation for K

A

(61.5) log 10 (Kout/Kin)

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4
Q

Changes of ion conductances will cause

A

Changed in membrane potential

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5
Q

Difference between an atrial and ventricular action potential?

A

Ventricular action potential lasts longer

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6
Q

In the typical ventricular action potential drawing (pg 4), what does phase 4 represent?

A

Resting Potential

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7
Q

Electrical activity in resting potential?

A

Outward K generated I-K2P current

Inward K current generates IK1 current

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8
Q

What does Phase 0 represent?

What electrical activity is going on?

A

Rapid Opening of voltage-gated sodium channels

I-Na current

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9
Q

What does Phase 1 represent?

What electrical activity is going on?

A

Closing of the voltage-gated Na channels

Voltage gated outward K curent

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10
Q

What does Phase 2 represent?

What electrical activity is going on?

A

The Plateau

Reduced outward K (I-K1) coupled with inward Ca current (I-Ca(L))

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11
Q

What does Phase 3 represent?

What electrical activity is going on?

A

Repolarization
Closure of L-type Ca channels
Increase in outward K (I-ks and I-Kr)

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12
Q

Inward rectifier channels close……

Example of an inward rectifier

A

when the cell depolarizes

I-K1

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13
Q

Difference between L-type and T-type Ca channels

A

T-types are in SA and AV nodes

L-types are in heart muscle cells for plateau

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14
Q

Name the five types of potassium currents

A 
Inward Rectifier
Slow delayed outward rectifier
Rapid delayed outward rectifier
leak channels
transient outward
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15
Q

Difference between effective refractory period and relative refractory period?

A

Effective – 2nd depolarization has no effect

Relative – Some channels are reset, more difficult to restim

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16
Q

Two sources of calcium in plateau stage

A

Ca enters through L type channels

Entering Ca triggers release from SR

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17
Q

How do catecholamines influence Ca levels?

A

Cate. act on beta-1 adren. receptors
Inc. cAMP and PKA
P of L-type Ca Channels
Increased inotropic state

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18
Q

How to block catecholamines on the heart?

A

beta-blockers

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19
Q

What might cause failure of the SA node? What would happen?

A

Occlusion of the sinus node artery

Pacemaker fxn taken over by AV node

20
Q

What is an escape rhythm?

A

When another pacemaker takes over for a defective SA

21
Q

What is an ectopic focus?

A

The area where spontaneous depolarization of a non-SA portion of the heart can occur

22
Q

Why are ectopic foci a concern?

A

They can trigger serious arrhythmias

23
Q

SA node has ______ stable resting potential.

A

No

24
Q

What is the pacemaker potential?

A

A slow depolarization of the cell caused by “funny current”

25
Q

Funny current mainly moves what ion?

A

Na

26
Q

What channels trigger SA action potential?

A

Initially Voltage gated T-type Ca channels

Later, L-type Ca channels open

27
Q

Describe the SA action potential cycle

A

P4 – Sodium Leak Current generates depolarizing prepotential
P0 – At -40mV, Ca channels open, triggering AP
P3 – Ca channels close, Na perm. decreases, K’s open

28
Q

Effect of PS stim on pacemaker?

A

Vagus decreases HR via Muscarinic ACh receptors
Increased K permeability in SA nodes
Takes longer for prepotential to reach firing threshold

29
Q

Effect of Symp. on pacemaker?

A

Stim HR via nore. on beta-1 adrenergic receptors
K channels close more rapidly
Less time for prepotential to reach firing threshold

30
Q

Route of electrical charge in pacemaker system

A 
SA depolarizes, Signal spreads through atrial myocardium
AV depolarizes
AV-bundle (Common Bundle of His)
L and R Bundle Branches
Purkinje Fibers
Ventricular Muscle Fibers
31
Q

Three parts of AV Node

A

Junctional, Nodal, Transitional

32
Q

Unique part of AV in the conduction pathway?

Why we care?

A

Delays conduction of the electrical impulses

Allows time for the atria to contract and relax before ventricular systole.

33
Q

Other name for fibrous portion of the heart?

A

Annulus fibrosis

34
Q

Cause of Wolf-Parkinson-White and Lown-Ganong-Levine syndromes?

A

Abnormal, accessory pathways that bypass the AV

35
Q

List Five things that influence conduction velocity.

A 
Sympathetic Stim (+)
Vagal Stim (-)
Hypoxia/Ischemia (-)
Adrenergic/Cholinergic (+/-)
Hyperkalemia/Cocaine (-)
36
Q

EKGs require ____ leads

A

12

37
Q

For ED patients with chest discomfort, an EKG should be performed within _______.

A

10 minutes

38
Q

Significance of P wave?

A

Dep. of atria

39
Q

Significance of P-R Interval

A

Time for impulse to pass through AV node

40
Q

Significance of QRS complex

A

Depolarization of ventricles

41
Q

Significance of T Wave?

A

Ventricular Repolarization

42
Q

Significance of S-T segment?

A

When elevated, indicates potential myocardial infarction

43
Q

Significance of Q-T Interval?

A

Prolonged in long-QT syndrome

44
Q

What is U wave?

A

Sometimes seen after T

Sign of hypokalemia, digoxin, quinidine

45
Q

What is J point?

A

Jxn of QRS and ST segment

46
Q

Where is the atrial repolarization in the EKG?

A

Hidden in the QRS

Cardio (10 decks)

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