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CABS2: Cardiology > Electrical Conduction ECG > Flashcards

Electrical Conduction ECG Flashcards

1
Q

What are the cardiac cells

A

Pacemaker cells
Electrical conduction cells
myocardial cells

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2
Q

what are pacemaker cells

A

electrical conduction point

SA node (60-100bpm)
AV node (40-60bpm)

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3
Q

what are electrical conduction cells

A

wiring of the heart

Bundle branches and perkinje fibers

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4
Q

where does the SA node receive blood from

A

the sinoatrial nodal artery off of the RCA

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5
Q

What stimulates the left atrium to contract

A

Bachman’s bundle

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6
Q

What affects the rate control of the heart?

A

Sympathetic stimulation increases rate (epi and norepinepherine)
parasympathetic lowers to normal (acetylcholine)

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7
Q

where does sinus rhythm originate

A

from the SA node

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8
Q

what does the fibrous skeleton act as

A

electrical insulator between the atria and ventricles

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9
Q

what is teh automaticity rate of AV node

A

40-60bpm

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10
Q

what is the normal length of PR segment

A

120-200ms (0.12-0.2sec)
less than 3 small boxes

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11
Q

what is the automaticity rate of the bundle branches

A

20-40bpm

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12
Q

What is the normal length of QRS complex

A

should be narrow (<100ms; 0.12 sec)
less than 3 small boxes

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13
Q

what occurs during the QRS complex

A

ventricular depolarization and contraction

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14
Q

what is R-prime

A

2nd upward deflection
with right bundle branch block

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15
Q

what is afib

A

irregularly irregular

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16
Q

What is resting membrane potential

A

difference in electrical charge across cellular membrane. transmembrane potential for cardiac myocytes is -90mV
- at baseline, there is a net negative charge within the cell

17
Q

what is action potential

A

rapid shift of cellular voltage

18
Q

what does the depolarization affect within the myocardial cell

A

affect the sarcolemma and spread to one another via the intercalated disks

19
Q

what is phase 4 during action potential

A

resting membrane portential is -90mV in cardiac myocyte with K+ predominantly intracellular
Na+ and Ca+ gates are closed

20
Q

What is phase 0 during action potential

A

stimulus
indicates that pacer cell has depolarized and transmits action potential to the myocytes beginning the action potential - transmitted via gap junctions
positive depolarization stimuli will cause Na+ channels to open

21
Q

What is phase 1 during action potential

A

early repolarization
begins when the fast Na+ gates close - only stay open for a few thousandths of a second
intracellular charge becomes positive
K+ flows out of the cell causing transmembrane potential to go back to 0

22
Q

what is phase 2 during action potential

A

the plateau phase
balance maintained near 0 by K+ going out, Ca2+ going into the cell
calcium initiates muscle contraction

23
Q

What is phase 3 during action potential

A

repolarization
transmembrane potential goes back to the resting state of -90mV with K+ flowing out and cessation of Ca2+ flowing in
Na+ and Ca2+ flow out of the cell

24
Q

what is the pacemaker action potential

A

Na+ will have slow, constant flow until transmembrane potential is -60mV - “funny current”

25
Q

when do the calcium channels open during pacemaker action potential

A

-55mV

26
Q

what is lacking in pacemaker action potential

A

no phase 2 or pause

27
Q

what is positive inotrope drugs

A

increases muscular contraction

28
Q

what are positive chronotropic drugs

A

increase HR (sympathetic - norepinepherine)

29
Q

what are negative chronotrop

A

decreases HR (parasympathetic - acetylcholine)

30
Q

what are the Beta receptors

A

Beta receptors (norepinepherine and epinepherine)
B1 - increase HR, increased contractility
B2 - inhibits smooth muscle contraction

31
Q

what are the alpha receptors

A

A1 - increases smooth muscle contraction -> increases BP
A2 - inhibits secretions

32
Q

What is normokalemia

A

K 2.5-5.0mM)
-90mV resting potential with higher concentration of K+ in the cell

33
Q

What is moderate hyperkalemia

A

K < 8mM
More K+ outside cell making cell partially depolarized.
Na+ channels (stage 0) are activated more quickly so increased excitability. early repolarization occurs causing peaked T waves

34
Q

What is Hyperkalemia

A

K > 8mM
Na+ channels can be inactive and K+ goes more into the cell so that cells are refractory (unexcitable) which will cause prolongation

35
Q

What is hypokalemia

A

low extracellular K+ will cause increased action potential (hyper-excitability)
ST depression, T wave inversion, U waves
** remember that hypokalemia and hypomagnesemia travel together

CABS2: Cardiology (11 decks)

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