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VET 408: Cardio/Respiratory > Cardiac Conduction & ECG Genesis > Flashcards

Cardiac Conduction & ECG Genesis Flashcards

1
Q

can specialized conduction cells contract and relax

A

no - can only generate action potentials

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2
Q

what happens if the SA and AV nodes fail

A

the bundles of His and Purkinje fibers have SLOW pacemaking ability

can generate 20-40 BPM

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3
Q

do cardiomyoctes have pacemaking ability

A

no - can only conduct current based on RMP and sodium channels

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4
Q

is conduction velocity the same across regions of the heart

A

no
SA node: slow - maintains rhythm
internodal: fast conduction
AV node: slow - allows adequate atrial filling before conducting signal to the ventricles
His bundle/purkinje - fast conduction for efficient contraction

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5
Q

where is the SA node located

A

junction where cranial vena cava enters right atrium

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6
Q

SA node conduction

A

spontaneous

FAST phase 4 to depolarization rate

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7
Q

what does ANS innervation of the SA node control

A

heart rate

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8
Q

how does the AP get conducted throughout the atrium

A

internodal tracts spread signal to:
1. left atrial myocytes
2. AV node

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9
Q

are atrial myocyte action potentials strong or weak

A

weak and short

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10
Q

function of the AV node

A

“gatekeeper”

controls and slows conduction to ventricles to maximize atrial filling

ONLY site that conducts atrial –> ventricular signaling

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11
Q

what structures can penetrate the fibrous skeleton of the heart

A

bundle of His & AV node

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12
Q

what does ANS innervation of the AV node control

A

conduction velocity

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13
Q

how does the AP get conducted throughout the ventricles

A

AV node –> His bundle –> L & R bundle branches –> Purkinje fibers –> ventricular myocytes –> epicardium and septum –> apex to base

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14
Q

are ventricular myocyte APs strong or weak

A

strong and long

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15
Q

left vs right bundle branches

A

L: 2 fascicles –> branch extensively
R: trabeculae septomarginalis (moderator band) spreads signal to the R ventricular wall

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16
Q

electrocardiogram (ECG)

A

graphic representation of summed electrical activity of the heart using electrodes on the body surface

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17
Q

what does an ECG measure

A

heart rate, rhythm, and conduction of electrical activity

chronotropy and dromotropy

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18
Q

chronotropy

A

initiating APs

affects HEART RATE

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19
Q

dromotropy

A

conducting APs

affects CONDUCTION VELOCITY

20
Q

what does an ECG not measure

A

cardiac function

inotropy and lusitropy

21
Q

inotropy

A

contractility of the muscle

22
Q

lusitropy

A

relaxation of the muscle

23
Q

what does the size and shape of the ECG waveform depend on

A
  1. direction of the current
  2. amount of tissue the current travels through
  3. speed (conduction velocity)
24
Q

current direction

A

the direction that the current spreads throughout the myocardium in relation to the + and - pole of the leads

25
Q

how does the waveform appear when the current moves toward the positive electrode

A

positive waveform

26
Q

how does the waveform appear when the current moves parallel to the positive electrode

A

small positive/negative waveform

27
Q

how does the waveform appear when the current moves away from the positive electrode

A

negative waveform

28
Q

what are ECG vectors

A

the average of the direction of current conduction across all cells

if current spreads in different directions in different cells –> ECG will display the AVERAGE of those directions

29
Q

how many ECG electrodes are there

A

3 +/- 1 ground electrode

RTL: white
LTL: black
LPL: red
RPL: green (ground electrode)

30
Q

bipolar leads

A

uses one positive and one negative electrode

setup lies within frontal plane to make a triangle around the heart

31
Q

lead I

A

RTL: -
LTL: +

current moves straight across from RTL –> LTL

32
Q

lead II

A

MOST COMMON
RTL: -
LPL: +

current moves diagonal from top right to bottom left

33
Q

lead III

A

LTL: -
LPL: +

current moves straight down left side

34
Q

augmented unipolar leads

A

single positive electrode lead in the frontal plane

averages all other electrodes to form the negative pole

records 1/2 voltage –> machine amplifies (aV)

35
Q

what are the unipolar leads

A

aVR: positive RTL
aVL: positive LTL
aVF: positive LPL

36
Q

base-apex lead

A

lead system used in large animals; primarily evaluates leads I and II

R jugular furrow: -
left apex: +

QRS complex is NEGATIVE in health

37
Q

does SA node depolarization show on ECG

A

NO - too small; assume it occurs before the P wave

38
Q

P wave

A

atrial myocyte depolarization

(rounded, slow)

39
Q

PQ interval

A

AV nodal and His bundle branch/purkinje fiber depolarization

(flat line between P and Q waves)

**ALL specialized conduction tissue has depolarized within PQ interval

40
Q

QRS complex

A

ventricular depolarization
Q: first negative deflection
R: first positive deflection
S: negative deflection after R; is NOT always present

41
Q

T wave

A

ventricular repolarization

(rounded wave)

42
Q

what is type A purkinje system

A

conduction occurs in three phases

starts at septum –> spreads to apex –> travels up to base

purkinje system is NOT deeply penetrating

causes a POSITIVE wave front

43
Q

what species have a type A purkinke system

A

dogs, cats, humans

44
Q

what is a type B purkinje system

A

conduction occurs in two phases

starts at septum –> spreads to base in rapid succession

purkinje system is deeply penetrating

causes a NEGATIVE wavefront

45
Q

what species have a type B purkinje system

A

hoses, ruminants, pigs, birds

46
Q

what is the most positive bipolar lead on a dog ECG

A

lead II (similar to aVF unipolar lead)

47
Q

what is the least positive bipolar lead on a dog ECG

A

lead I

VET 408: Cardio/Respiratory (38 decks)

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