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A/P > Lecture 10/21 & 10/23: Cardiac > Flashcards

Lecture 10/21 & 10/23: Cardiac Flashcards

Test 4

1
Q

T/F: you cannot generate an AP in the absolute refractory period.

A

T

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2
Q

What happens if you generate an AP in the relative refractory period?

A

You might not get an AP or get an odd AP

Pumping in heart will take a hit

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3
Q

What is the main pacemaker of the heart? Why?

A

The SA node

Higher Vrm so depolarizes and reaches threshold potential faster than any other tissue in the heart -> able to generate AP fastest

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4
Q

The _____ vagus nerve stimulates the SA node
The ______ vagus nerve stimulates the AV node

A

Right

Left

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5
Q

T/F: some branches of vagus nerve extend past SA/AV node

A

T

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6
Q

Which nervous system is the main innervation of the pacemakers of the heart?

A

PNS - vagus

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7
Q

Which nervous system is strongest in the atria and ventricles?

A

SNS

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8
Q

What is the function of the Vagus nerve at the SA node?

A

suppression of activity of pacemaker cells

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9
Q

The SA node generates an AP every ______ seconds in a healthy person

A

0.83 seconds

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10
Q

The SA node generates AP at ______ b/m in a healthy person

A

72

use this exact number

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11
Q

Without vagal and SNS input, how often would the SA node generate an AP?

A

110 b/m

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12
Q

Without vagal but with SNS input, how often would the SA node generate an AP?

A

120 b/m

SNS raises by 10 b/m

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13
Q

If we only had Vagal input, how often would the SA node generate an AP?

A

60-62 b/m

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14
Q

What are our main catecholamines that effect that SNS in the heart?

A

NE -> Beta-R

Ach -> mAch-R (dominates)

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15
Q

T/F: SNS effects in the heart are local

A

F

More widespread in atria/ventricles

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16
Q

SA node AP: Describe phase 4

A

“Diastolic depolarization”
The steeper the slope = faster HR
Slope d/t increase in membrane potential d/t leaky Ca++ & Na+ channels and HCN channels

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17
Q

Describe L-type Ca++ channels

A

Open slow and stay open longer (close slow)

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18
Q

SA node AP: Describe phase 0

A

Upstroke of AP
Less upstroke than ventricles d/t no fast Na+ channels
Slow L-type Ca++ channels open

Important for determining how fast AP gets to each cell around the heart via gap junction

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19
Q

SA node AP: Describe phase 1

A

HAHA there is no phase 1

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20
Q

SA node AP: Describe phase 2/3

A

Slow L-type Ca++ channels closing
V-G K+ channels open

Repolarization/Reseting of the cell
Phase 2&3 are combined
SOMETIMES THIS IS ONLY REFERRED TO AS PHASE 3

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21
Q

What is the Vrm in the SA node?

A

-55 mV

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22
Q

What is the threshold potential in the SA node?

A

-40 mV

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23
Q

Describe where the HCN channels are?

A

highest density = SA node

alot in the AV node

Sparcely in ventricles

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24
Q

When can the heart generate an AP?

A

When you go from Vrm to threshold potential

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25
Q

When do HCN channels open?

A

At Vrm:
after repolarization or during hyperpolarization

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26
Q

What does HCN channels mean?

A

Hyperpolarization & cyclic nucleotide mediated channel

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27
Q

What cations pass through HCN channels?

A
  1. Na+ (primary)
  2. Ca+
  3. K+ (not as much)
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28
Q

Describe pathway of beta agonists on Beta-R with HCN channels

A

Beta agonists increases cAMP
cAMP = cyclic nucleotide –> opens HCN channels –> increase phase 4 slope = decreased time to get to threshold potential –> more AP = increased HR

Ex) Epi, NE

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29
Q

Describe pathway of Muscarinics on the mAch-R with HCN channels

A

Increase Ach = increase in K+ permeability & decrease in cAMP –> decreases Vrm & decreases HCN channels –> increases time to get to threshold potential –> less AP = decreased HR

Decrease Ach = decrease K+ permeability –> increase Vrm –> decrease time to get to threshold –> increases HR

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30
Q

Small amount of hyperkalemia has what effect on the heart?

A

Small increase in HR

not applicable to high level increases

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31
Q

You increase Vrm by _____ concentration gradient of K+
This will increase HR

A

Decreasing

(Less K+ movement)

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32
Q

How does Ca++ effect threshold potential?

A

MOA is unknown but it does in heart tissue only

Increase in Ca++ = increase threshold potential –> increase phase 4 = decrease HR

Decrease in Ca++ = decreases threshold potential –> decreases phase 4 = increase HR

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33
Q

How fast can the AV node generate an AP?

A

40-60 b/m

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34
Q

How fast can the purkinje fibers generate AP?

A

15-40 b/m

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35
Q

T/F: You dont need the atria to fill the ventricle
Why?

A

T

Purkinje fibers are able to fire an AP but the ventricles wont fill properly. BP will be decreased

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36
Q

The ______ is the conduction system of the ventricles and the _______ is the conduction system of the right atria

A

Purkinje fibers

Internodal pathways

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37
Q

How does electricity travel in a healthy heart?

A

SA node –> internodal pathways –> L atria, R atria, & AV node –> Bundle of His –> L BB –> R BB –> Purkinje fibers –> Ventricles –> Last piece of lateral L ventricle

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38
Q

What is the last part of the heart to be depolarized?

A

Lateral piece of left ventricle

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39
Q

What are the three internodal pathways from right to left?

A

Posterior
Middle
Anterior

PMA

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40
Q

How long does it take to go through the internodal pathways?

A

0.03 seconds

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41
Q

How is the L atria depolarized?

A

Interatrial bundle

A bundle of connective tissue from the internodal pathways that help get electrical signal to the L atria

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42
Q

Where is the internodal pathways?

A

R atria

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43
Q

How long does it take to depolarize the R atria?

A

0.07 seconds

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44
Q

How long does it take for electricity to get from the SA node to the end of the interatrial bundle?

A

0.07 seconds

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45
Q

How long does it take for the L atria to be depolarized?

A

0.09 seconds

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46
Q

What is the time difference between the end of the interatrial bundle and depolarization of the L atria? Why?

A

0.02 secs

There no specialized conduction tissue there. Only muscle cells with myofibrils and myofibriles dont conduct electricity very fast

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47
Q

How long does it take to completely depolarize the heart in a healthy person?

A

0.22 secs

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48
Q

What is another name for the Interatrial bundle?

A

Bachman’s bundle

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49
Q

L atria depolarization is ___ seconds and means all atrias are ________. This represents a ____ wave on the EKG

A

0.09

depolarized

P

50
Q

What is the purpose of the delay at the AV node?

A
  1. Gives atria time to contract to help fill ventricles before they start contracting
  2. Filters crazy electrical activity in the atria from causing an AP during refractory period
51
Q

What happens if there’s an AP during a refractory period?

A
  1. You may not generate another AP
  2. You may generate an odd AP
52
Q

How long does it take to get to the AV node from SA node?

A

0.03 sec

53
Q

What causes the delay at the AV node?

A
  1. AV node is fat, fat, doesn’t conduct, electricity well
  2. Low amount of gap junctions present
54
Q

How long of a delay does the AV node cause?

A

0.12 sec

55
Q

How long of a delay does the Bundle of His cause?

A

0.01 sec

56
Q

How long of a delay does the bundle of His and the AV node cause?

A

0.13 secs

57
Q

How long does it take for electricity to get to the bundle branches? What does this indicate?

A

0.16 sec

PR interval

58
Q

How long is the PR interval?

A

0.16 secs

59
Q

What branches off the Bundle of His?

A

L & R BB –> Ventricular septum –> Purkinjie fibers

60
Q

T/F: when a cell is at rest, there is no charge.

A

T

61
Q

T/F: You will see the largest deflection when most the tissue is depolarized and a small amount of tissue is at rest

A

F

largest when half is depolarized and half at rest

62
Q

T/F: electrons moving towards the positive electrode in depolarization, shows as a positive deflection in a healthy heart

A

T

63
Q

Repolarization of the atria happens in the ______ direction of depolarization. Repolarization of the ventricles happens in the _____ direction of depolarization.

A

Same

Opposite

64
Q

If electrons are moving towards the positive lead = ________ deflection. If electrons moving towards negative lead = ________ deflection.

A

positive

negative

65
Q

Depolarizing is adding _____ signs
Repolaring is adding ______ signs
Resting tissue is ______ signs

A

negative (-)

positive (+)

positive (+)

66
Q

Describe ventricle repolarization

What effect does this have on EKG lead II readings

A

Repolarizing in the opposite direction of depolarization.

From Epicardium to Endocardium (Superficial to deep)

This presents as a positive deflection T-wave

67
Q

How do the ventricles depolarize? How does this show up in EKG lead II

A

L&R ventricles
Then endocardium to epicardium

QRS positive deflection

68
Q

Atria & ventricle depolarization happens from _________. Atria repolarization happens from ________. Ventricle repolarization happens from ________.

A

R - L

R - L

L - R

69
Q

What is the average mean electrical axis of a healthy heart? Where is it pointed?

A

59 degrees

L foot

70
Q

During early stages of depolarization the _________ is depolarized

A

L side of the ventricular septum

71
Q

Where do electrons want to move?

A

Towards + charges

resting/repolarized tissues

72
Q

What does the magnitude of deflection depend on?

A

How much tissue is depolarized vs how much tissue is remaining at rest

73
Q

What does an EKG measure?

A

The sum of all current that’s found between electrodes on the body

74
Q

What is considered a fast AP? Why?

A

Ventricular conduction systems:AP by the ventricles or the purkinje fibers

phase 0 is very steep d/t fast Na+ channels

75
Q

What is the normal magnitude of depolarization in the ventricles in an AP?

A

100 mV

76
Q

How much of a deflection from the ventricles are you supposed to see in an EKG? How many big & small boxes is this?

A

about 1.5 mV

3/4 big boxes or

15-20 small boxes

77
Q

Ventricular depolarization starts in the ______ layer

A

endocardium

78
Q

What is the muscle cell in the ventricles called?

A

Ventricular myocyte

79
Q

After phase _____ all tissue should be repolarized

A

3

80
Q

What causes chronic depolarization?

A

injury/infarct/ischemia

81
Q

T/F: An injured area can repolarize

A

F

An injured area is chronically depolarized.
It gives off NEGATIVE VIBES
It cannot be repolarized

It generates a current of injury

82
Q

COI =

A

Current of injury

83
Q

What is the QT interval?

A

Depolarization and repolarization of the ventricles

84
Q

Why is there a huge loss of voltage displayed in 3-lead EKG from AP?

A

Resistance in heart tissue & where electrodes are places. Farther away from heart, fat and air reduce voltage picked up.

V-leads are closer to heart so you see a larger deflection in them

85
Q

How is an injury represented?

A

negative (-) signs

86
Q

Where will you see abnormal current from an injury in an EKG?

A

Where we should not have any current.

End of T-wave –> Beginning of P-wave

87
Q

EKG interpretations lead II: Why would you see an inverted P-wave?

A

P wave originated in the AV nodes and electrical current traveled from AV node to SA node

88
Q

EKG interpretations lead II: Describe the P wave

A

Atria depolarization

0.09 sec long

2.5 boxes long & tall

89
Q

T/F: Air & fat helps increase electricity conduction

A

F

Decreases conduction

90
Q

What condition of the lungs can decrease conduction of electricity in EKGs?

A

COPD

91
Q

Losing conduction of electricity in EKG d/t fat & air will result in _____

A

smaller QRS complexes

92
Q

EKG interpretations lead II: If the P-wave is taller than normal, what does this indicate?

A

R atria problem –> R atria hypertropy (enlargement)

93
Q

EKG interpretations lead II: If the P-wave is longer than normal, what does this indicate?

A

L atria problem –> L atria too stretched out

94
Q

EKG interpretations lead II: If the P-wave has a double hump, what does this indicate?

A

Block preventing spread of electrical activity to L atria

(block at the interatrial branch or bachman’s branch)

95
Q

EKG interpretations lead II: Describe a Q-wave

A

Negative deflection before R-wave
All readings wont always have Q-waves

Beginning of Ventricles depolarization

96
Q

EKG interpretations lead II: Describe R-wave

A

positive deflection above baseline

Corresponds with half the ventricles being depolarized

97
Q

EKG interpretations lead II: Describe QRS complex

A

positive deflection
About 1.5 mV or 3/4 big boxes

Lasts about 0.06 secs

98
Q

EKG interpretations lead II: Describe S-wave

A

Negative deflection after R-wave

99
Q

Why is the Q- wave and S-wave negative deflections?

A

Q-wave: the venticular septum depolarizing from L to R at the beginning of depolarization of the ventricles

S-wave: The last part of the ventricles to depolarize is a small part of the L lateral part of the ventricle.

100
Q

EKG interpretations lead II: Where is the atria repolarized?

A

Hidden within QRS

101
Q

What condition of the heart can cause large QRS complexes?

A

Extra ventricular tissue –> Dilated cardiomyopathy

102
Q

What does the end of the QRS indicates?

A

All ventricular tissue is depolarized

103
Q

What is the J-Point?

A

“Isoelectric point”

end of QRS after S wave where all ventricular tissue is depolarized.

104
Q

EKG interpretations lead II: Describe T-wave

A

Ventricular repolarization

Positive deflection d/t repolarization of epicardium to endocardium

105
Q

Where does odd electrical activity show up from chronically injured tissue in EKG?

A

After T wave and Before P wave

In healthy hearts, there will be no current here

106
Q

EKG interpretations lead II: Describe QT interval

A

Ventricular septum depolarization –> venticular repolarization

0.25 - 0.35 seconds
(Endocardium fastest AP)

107
Q

What is the ST interval useful for?

A

Identifying areas of Ischemia/Infarct

108
Q

What is the physiological reasoning behind increased HR in running a marathon?

A

ST interval decreases –> decreases QT interval –> Able to fire an AP quicker –> increases HR

Lusitropy

109
Q

Define lusitropy

A

Resetting of the ventricles faster than it normally does to increase HR

110
Q

Define inotropy

A

Dealing with the strength of contraction

111
Q

Define dromotropy

A

Speed of conduction of electrical current

Depends on NA+

Increased Na+ = Increased transmission

112
Q

Define chronotropy

A

HR

113
Q

What is the formula for HR?

A

(60 secs) / (RR interval) = HR

114
Q

What is normal RR interval?

A

0.83 seconds

115
Q

What was the rate at which they would feed EKG paper through the machine?

A

25 mm/sec

116
Q

In an EKG strip, how many mV is a large box?

A

0.5 mV

117
Q

In an EKG strip, how many mV is a small box?

A

0.1 mV

118
Q

What axis is the mV on in an EKG?

A

Vertical (Tall)

119
Q

In an EKG strip, how many seconds is a large box?

A

0.2 seconds

120
Q

In an EKG strip, , how many seconds is a small box?

A

0.04 seconds

121
Q

What axis is the seconds on in an EKG?

A

Horizontal (Long)

A/P (25 decks)

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