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CARDIO EXAM 1 > Lecture 3: EP > Flashcards

Lecture 3: EP Flashcards

1
Q

What is the P wave:

A

atrial depolarization
-happens immediately following SA node firing

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2
Q

PR interval

PR segment:

A

initial depol of ventricle/excitation

PR segment: delay at AV node

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3
Q

PR interval varies with conduction velocity via:

A

AV node

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4
Q

AV node conduction velocity and PR interval relationships

A

indirectly proportional

if AV node conduction decreases (heart block), PR invterval increases

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5
Q

by stimulating parasympathetic system: PR interval is inc/dec? HOW ABOUT THE AV CONDUCTION VELOCITY?

A

PR invterval is INCREASED (dec conduction velocity of AV node)

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6
Q

sympathetic stimulation dec/inc PR? AV node velocity conduction?

A

PR is decreased (increases conduction velocity of AV node)

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7
Q

QRS interval:

A

depolarization of ventricles

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8
Q

QT invterval

A
  • begining of Q, end of T
  • entire period of depol & repolarization of ventricles–> ventricular AP
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9
Q

ST segment

A

-end of S to begining of T
-isoelectric
- ventricles are depolarized
- -ventricles are contracting & emptying ~corresponds to plateau phase of ventricular AP

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10
Q

T-wave

A

ventricular repolarization

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11
Q

Cardiac action potential, the RMP is determined by:

A

conductance of K+ & approaches to K+ equilibrium

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12
Q

inward current

A

brings positive charges INTO CELL and depolarizes

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13
Q

outward current:

A

takes positive charges out of the cell & hyperpolarizes

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14
Q

what maintains ionic gradients across the membrane?

A

Na+,K+-adenosine triphosphatase (ATPase) maintains ionic gradients
across cell membranes

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15
Q

the image is ventricular (non-pacemaker/rapid!!) action potential, what is phase 0?

A

**is the upstroke of the action potential

-** increase in Na+ conductance–>inward current–>depolarizes the membrane**

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16
Q

the image is ventricular action potential, what is phase 1?

A

is a brief period of initial repolarization.“transiently outward K+”
- caused by an outward current of K+ions out of the cell & a decrease in Na+ conductance (inactivation of Na)

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17
Q

the image is ventricular action potential, what is phase 2?

A

is the plateau of the action potential.
■ is caused by a transient increase in Ca2+ conductance via L-type long lasting channels–>inward Ca2+current & by an increase in K+ conductance
■* During phase 2, outward and inward currents are approximately equal/balanced, so the
membrane potential is stable at the plateau level.*
- IKs- voltage stays close to 0 (Ca influx countering K outlfux)

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18
Q

the image is ventricular action potential, what is phase 3?

A

is repolarization.
■** Ca2+ conductance decreases (close), and K+ conductance increases**
■ The high K+ conductance results in a large outward K+ current (IK)–>hyperpolarizes
the membrane back toward the K+ equilibrium potential.
**

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19
Q

the image is ventricular action potential, what is phase 4:

A

is the resting membrane potential.

  • is a period during which **inward and outward currents (IK1) are equal **and the mem-
    brane potential approaches the K+ equilibrium potential.
    -the small fluxes of Na+ (influx) & K+ (outflux)maintain the resting potential
  • this entire graph is a RAPID DEPOLARIZATION OF THE non-pacemaker cell AP (ventricular AP)–> bc rapid~ referred to as a FAST RESPONSE
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20
Q

Sinoatrial (SA) node
(slow response)

A
  • normally the pacemaker of the heart
  • unstable resting potential
  • -has phase 4 depolarization/automacity
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21
Q

Sinoatrial (SA) node
phase 0:

A
  • upstroke of the action potential.
    ■ is caused by an increase in **Ca2+ conductance. **–> inward Ca2+
    current     that drives the membrane potential toward the Ca2+ equilibrium potential.
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22
Q

how is phase 0 different in the ventricles,
atria, and Purkinje fibers vs. SA node?

A

The ionic basis for phase 0 in the SA node is different from that in the ventricles,
atria, and Purkinje fibers (where it is the result of an inward Na+ current in the non-pacemaker).

in the SA node: there is Ca+ inward current

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23
Q

SA node phase 3:

A
  • repolarization.
    ■ is caused by an increase in K+ conductance. –>results in an outward K+
    current –> repolarization of the membrane potential.
    ~60mV
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24
Q

SA node phase 4:

A

- slow depolarization.
- * accounts for the pacemaker activity of the SA node (automaticity).*
-caused by an **increase in Na+ conductance, **–> inward Na+ current
called If.
■ If is turned on by repolarization of the membrane potential during the preceding
action potential.
- dec outward K (Ik) & gradual influx of Ca+ as threshold is approached

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25
Q

which phases does SA node not have?

A

phase 1 & 2

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26
Q

which pacemaker fires 60-100 depols per min?

A

SA node

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27
Q

what is the secondary pacemaker that takes over regulation of the heart if the primary pacemaker of the heart is damaged?

A

AV node

28
Q

which pacemaker fires 40-50 depols/min?

A

AV node

29
Q

this pacemaker takes over only if the primary AND secondary pacemakers are damaged:

A

bundle of His/Purkinje fibers

30
Q

this pacemaker fires 20 depolarizations per minute:

A

bundle of His/Purkinje fibers

31
Q

the heart receives sympathetic innervation from the ________

A

thoracic spinal cord (cardiac plexus)

32
Q

the heart receives parasympathetic innervation from the ________

A

vagus nerve

33
Q

which type of innervation releases acetyl choline to SA node?

A

parasympathetic

34
Q

voltage gated K+ channels closing more slowly - hyperpolarizes resting potential, is an effect of _________ innervation on the heart

A

parasympathetic

35
Q

decreased If (funny)– reduces slope of phase 4 depolarization, is an effect of _________ innervation on the heart

A

parasympathetic

36
Q

NT of the para & sympathetics?

A

Ach (para) & NE (symp)

37
Q

HR in
para & symp?

A

para: dec HR
symp: inc HR

38
Q

increased If (funny) in nodes and ICa in all myocardial cells, is an effect of _________ innervation on the heart

A

sympathetic

39
Q

the lowering of the threshold is an effect of _________ innervation on the heart

A

sympathetic ASK*

40
Q

what causes a stronger and faster contraction in the heart?

A

increasing intracellular Ca++

41
Q

what is the “resting potential” of pacemaker cells?

what is the resting potential of non-pacemaker cells?

A

pacemakers: -60mV
non-pacemakers: -90mV

42
Q

the absolute refractory period for non-pacemaker cells includes what phases?

A

0-3

43
Q

during absolute refractory period for non-pacemaker cells, what channels are inactivated?

A

Na+ channels

44
Q

what is the significance of the absolute refractory period?

A

-allows time for ventricular filling between beats
-prevents the heart from summing twitches or tetanizing

45
Q

In atrial and ventricular myocardium it is primarily by cell-cell contact through _________

A

gap junctions

46
Q

from the SA node, what is the order of the spread of impulse?

A

SA node–>septum–>apex –> base/endocardium –> epicardium

47
Q

the only conducting pathway from the atria into the ventricle comes from the _______

A

AV node

48
Q

where does the AP begin?

A

SA node

49
Q

SA conduction pathway

A

SA node–>atrial muscles–>AV node–>bundle of HIS–>left & right bundle branches–>purkinjie fibers

50
Q

conduction arriving in the L& R purkinjie branches allows:

A

stimulation to ramify down the endocardial surfaces of the septum spreading laterally

51
Q

how does the heart conduction system spread the impulses into the ventricular myocardium to individual myocytes?

A

Purkinje fibers

52
Q

ventricular repolarization spreads “_________” over the pathway of depolarization

A

backwards

53
Q

though the _________ are the last to depolarize, and the first to repolarize

A

subepicardial myocytes

54
Q

the _________ are the last to repolarize

A

left and right bundle branches

55
Q

When a dipole vector indicating depolarization points toward the** + electrode**, the signal is ________

A

positive

56
Q

When a dipole vector indicating depolarization points away the + electrode, the signal is ________

A

NEG

57
Q

When a dipole vector indicating repolarization points toward the + electrode, the signal is __________

A

positive

58
Q

Electrodes placed perpendicularly to a dipole vector show __________

A

no deflection

59
Q

Electrodes placed perpendicularly to a dipole vector show __________

A

no deflection

60
Q

the largest + and - signals occur when the mean electrical vector is ________ to the electrodes

A

parallel

61
Q

No signal can be detected when the vectors are _____________ to the electrodes

A

perpendicular

62
Q

to achieve Einthoven’s triangle, where are leads placed on the body?

A

left arm, right arm, left leg

63
Q

Einthoven’s triangle

A

This arrangement of electrodes allows measurement of cardiac depolarizations along three electrical axes:

64
Q

Because the limb leads are assumed to form an equilateral triangle, they can form an axial coordinate system with lead I at what degree ___

A

0°

65
Q

Because the limb leads are assumed to form an equilateral triangle, they can form an axial coordinate system with** lead II** at ___

A

60°

66
Q

Because the limb leads are assumed to form an equilateral triangle, they can form an axial coordinate system with lead III at ___

A

120°

67
Q

where does AP begin?

A

SA node

CARDIO EXAM 1 (5 decks)

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