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A&P 2024 > Cardiac Lecture 2 > Flashcards

Cardiac Lecture 2 Flashcards

exam 4

1
Q

The action potential of ______ tissue is considered a “Fast AP” because phase 0 slope is steep

A

Ventricular

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2
Q

Normal healthy heart rate

A

72bpm

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3
Q

Why is the SA node considered the pacemaker of the heart

A

It reaches threshold faster than anywhere else in the heart.

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4
Q

What is the magnitude of deflection of an EKG?

A

1.5mV

The mV between the lowest point and peak of R wave

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5
Q

What is the Vrm in the SA node?

A

-55mV

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6
Q

What is the threshold mV in SA node

A

-40mV

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7
Q

Which channel is responsible for the steep phase 4 in SA node action potential?

A

HCN

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7
Q

When do HCN channels open

A

Opens at Vrm or by cAMP

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7
Q

What ions can diffuse through HCN channel

A

Non-specific to + charged ions (cations). Primarily Na+ and Ca++ enter cell. (K+ can technically leave through, but usually leaves elsewhere)

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8
Q

What is an HCN channel

A

Hyperpolarization cyclic nucleotide channel

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8
Q

EKG is the sum of all _____ of cardiac electrical activity

A

current

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8
Q

Vrm in ventricular myocyte

A

-80mV

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8
Q

Peak of AP in ventricular myocyte

A

+20mV

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9
Q

1 big box on EKG is _____ mV

A

0.5mV

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9
Q

1 big box on EKG is ____ sec/msec

A

0.2 seconds/ 200ms

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9
Q

what is occuring at the P wave?

A

atrial depolarization

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10
Q

what is occuring at the QRS

A

ventricular depolarization and atrial repolarization (can’t see atrial repolarization because of ventricular depol)

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11
Q

What is occuring at the T wave

A

ventricular repolarization

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12
Q

Electrons moving _______ the positive lead results in a positive deflection

A

towards

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13
Q

Electrons moving _______ the positive lead results in a negative deflection

A

away

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14
Q

Electrons moving ______ the negative leads results in a negative deflection

A

towards

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15
Q

Electrons moving _______ the negative lead results in a positive deflection

A

away

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16
Q

Depolarization occurs first in the ________ and spreads _______ towards the ________

A

endocardium, superficially, epicardium

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17
Q

Repolarization occurs first in the _______ and spread _______ towards the _______

A

epicardium, deep, endocardium

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18
Q

One large box on EKG contains how many small boxes?

A

5 wide and 5 tall for 25 total

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19
Q

Why is the T wave a positive deflection

A

Because repolarization starts in epicardium and travels deep towards the endocardium. Repolarization occurs in the opposite direction, resulting in a + deflection on EKG.

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20
Q

Ischemia prevents electrical ______ of tissue

A

resetting/repolarization

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21
Q

Ischemic tissue is _______ constantly

A

depolarized

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22
Q

Current of injury where there should not be any

A

Ischemic tissue depolarization

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23
Q

Why is EKG current lower mV than actual AP

A

Voltage lost due to high resistance of tissue/fat/air between myocyte and superficial leads; air - COPD

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24
Q

muscle layer that is very deep in the wall of heart (only in left ventricle)

A

subendocardium

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25
Q

usual location of an MI because pressures are the highest, and furthest from blood supply

A

subendocardium

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26
Q

inner, stretchy layer of pericardium

A

parietal pericardium

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27
Q

outer, fibrous layer of pericardium (thick leathery, similar to dura layer)

A

fibrous pericardium

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28
Q

The myocardium is ________ muscle meaning it’s a network of cells that function as a single unit

A

unitary

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29
Q

Vrm of purkinje fibers

A

-90mV

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30
Q

what is five and dime reflex?

A

the stimulation of the ophthalmic branch of the trigeminal nerve (CN V) that triggers brainstem to stimulate the vagus nerve (CN X) causing bradycardia/asystole

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31
Q

Phase 0 of AP occurs because of

A

opening of VG-Na+ channels once threshold is reached

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32
Q

Phase 1 of AP occurs because of

A

VG-Na+ channels close, K+ channels close, fast T-type Ca++ channels open.

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33
Q

Phase 2 of AP occurs because of

A

slow L-type Ca++ channels open causing plateau

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34
Q

Phase 3 of AP occurs because of

A

K+ channels open back up until Vrm reached

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35
Q

Ohm’s law

A

V= I x R

V= voltage, I= current, R= resistance

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36
Q

Majority of vagus nerve affects what area of the heart

A

nodal areas (SA/AV nodes)

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37
Q

Parasympathetic effects are more _______ and sympathetic effects are more ________ in the heart

A

focal, widespread

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38
Q

Primary catecholamine in heart

A

norepi

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39
Q

increase of cAMP would do what to HR

A

increase

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40
Q

What is blood Ca++ levels effect on threshold

A

inc. Ca++ = inc. threshold (more +) = dec. HR

dec. Ca++ = dec threshold (more negative) = inc. HR

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41
Q

How does mACh-R affect HR?

A

binding of ACh on mACh-R causes them to open and increases K+ permeability, making Vrm more negative and decreasing HR.

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42
Q

How is the anatomy of the gap junctions in the heart different from other muscles?

A

Intercalated discs - allows more gap junctions d/t increased surface area, curvy/indentations instead of flat

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43
Q

Each cardiac muscle cell has how many nuclei?

A

one

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44
Q

The term used to describe the connection between one heart cell and another is ______

A

intercalated discs - only found in heart

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45
Q

What are the 2 mechanisms heart cells use to replace heart cells that have died?

A
  1. Stem cells - slow repair process
  2. Fibroblasts - lay down scar tissue where stem cells are overwhelmed
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46
Q

Multinucleated cells think _______

A

skeletal muscle

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47
Q

______ is the condition where fibroblasts are laying down extra scar tissue than normal. _______ are the class of medications used to prevent this

A

CHF; ACE inhibitors

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48
Q

How do ACE inhibitors prevent unnecessary scar tissue formation in the heart?

A

ACE inhibitors inhibit growth factor side of angiotensin II

49
Q

What are the 2 issues with having scar tissue in the heart?

A
  1. doesn’t conduct action potential
  2. doesn’t contract
50
Q

ACE inhibitors are known to reduce ______

A

afterload

51
Q

Conduction tissue is good at transmitting AP because it doesn’t have _______

A

myofibrils

52
Q

_______ describes the arrangement of the heart muscle in two distinct ventricular layers that twist in different directions

A

Syncytial connections

53
Q

Above the AV node

A

Top half - atria

54
Q

Below the AV node

A

lower half of the heart - ventricles

55
Q

The vast majority of heart cells are _______

A

myocytes - muscle tissue, used to produce force via myofibrils

56
Q

What are the 2 types of tissue in the heart?

A
  1. Muscle tissue
  2. Conduction tissue
57
Q

The _______ is the one-cell thick layer in the endocardium

A

endothelial layer

58
Q

The _______ is the muscle layer that is located between the myocardium and endocardium

A

Subendocardium

59
Q

The bulk of the heart muscle wall is in the ______

A

myocardium

60
Q

The pericardial space is filled with ______ and _____ to prevent friction in the pericardium

A

fluid and mucus

61
Q

Typically all the major blood vessels of the heart are sitting on top of the _______

A

epicardium

62
Q

Pain in the pericardium can be caused by what 2 things?

A
  1. Inflammation
  2. Loss of fluid/mucus
    - both cause increased friction
63
Q

The pericardium consists of what 3 layers?

A
  1. Pericardial space
  2. Serous pericardium - parietal
    and visceral layers
  3. Fibrous pericardium
64
Q

The ______ is the outer layer of the pericardium that is stiff and similar to the dura layer

A

fibrous pericardium

65
Q

What are the 2 layers of the serous pericardium?

A
  1. Visceral layer - thin/elastic layer that sits between parietal layer and the heart tissue
  2. Parietal layer - connected to the fibrous pericardium
66
Q

The visceral pericardium is also known as the _______

A

epicardium

67
Q

The heart, when relaxed, is not relaxed to an optimum degree. It is _______

A

under-stretched - no H band, actin and myosin overlapping

68
Q

The ________ is the conduction system within the ventricular muscles

A

purkinje fibers - don’t contract, ventricles do contract

69
Q

Threshold potential for both Purkinje and ventricular cells is _____

A

-70mV

70
Q

Sodium permeability in myocytes is not ______, giving phase ____ a slope

A

constant, phase 4

71
Q

Sodium permeability ______ as time goes by in myocytes, allowing _______ depolarization

A

increases, spontaneous or self depolarization

72
Q

How long does it take for the Purkinje fibers to self-depolarize?

A

30+ seconds

73
Q

What is the length or duration of the AP in the heart?

A

200ms

74
Q

Phase ___ indicates length of contraction

A

2

75
Q

_____ is the primary neurotransmitter of the PANS that affects the heart. What receptors does it interact with?

A

ACh, mACh-R

76
Q

_____ is the primary neurotransmitter of the SANS that affects the heart. What receptors does it interact with?

A

Norepinephrine - interacts with beta receptors

77
Q

The PANS primarily innervates what tissue in the heart? What about the SANS?

A

PANS - nodal tissue
SANS - ventricular tissue

78
Q

The total change in electrical activity of a ventricular myocyte from it’s resting state to its activated state is ______ mV

A

100

79
Q

If the normal HR is 72 bpm, how often is an AP fired?

A

every 0.83 seconds

80
Q

By itself, the SA node will beat at ____ bpm

A

110

81
Q

SANS activity without vagal input would cause the heart to beat at _____ bpm

A

120

82
Q

PANS or vagal input w/o SANS input would cause the heart to beat at ____ bpm

A

60-62

83
Q

What effect would beta antagonists have on the heart? Why?

A

Beta-blockers will decrease cAMP and therefore cause less activation of HCN channels, decreasing the slope of phase 4 in the nodal tissue action potentials, and decreasing HR

84
Q

What would the HR be if just the AV node if firing?

A

40-60 bpm if no SA node AP

85
Q

What would the HR be if just the purkinje fibers were firing?

A

15-30bpm

86
Q

Which layer of the heart would have the longest AP?

A

Endocardium

87
Q

What effect would beta-agonists have on the heart? Why?

A

Beta-agonists will increase cAMP and therefore cause more activation of HCN channels, increasing the slope of phase 4 in the nodal tissue action potentials, and increasing HR

88
Q

Hypocalcemia causes ____ in the heart by _____. Hypercalcemia causes ____ in the heart by _____.

A

Hypocalcemia - tachycardia, decreasing threshold potential
Hypercalcemia - bradycardia, increasing threshold potential

89
Q

Mild hyperkalemia would result in _______

A

tachycardia because the Vrm would be higher (more depolarized) and thus require less time to reach threshold potential.

90
Q

What ions are nodal tissue most permeable to during phase IV?

A

Calcium and sodium - via HCN and leak channels

91
Q

Differentiate between effects of potassium permeability vs beta-adrenergic receptors vs calcium permeability

A

Potassium - changes the Vrm
Beta-adrenergic - changes the slope
Calcium - changes the threshold potential

92
Q

How is HR calculated from an ECG?

A

60 seconds divided by R-R interval (0.83 seconds) = 72 bpm

93
Q

______ is the speed of electrical conduction

A

dromotropy

94
Q

______ is the force of contraction

A

ionotropy

95
Q

______ is the frequency at which the heart fires an AP

A

chronotropy

96
Q

________ is how fast the ventricles reset or relax during diastole

A

Lusitropy, length of ST segment

97
Q

How fast did the ECG paper feed back in the old days?

A

25mm/sec

98
Q

What is the average angle in which the heart fires an AP?

A

59 degrees, towards left foot

99
Q

Phase IV of SA node depolarization is also called what? What does it determine?

A

Diastolic depolarization - determines HR

100
Q

What ion channels determine the decreased slope of phase 0 in SA node depolarization?

A

L-type Ca++ channels - less permeable to Na+ than in ventricles

101
Q

SA node depolarization doesn’t have a phase __

A

1, and doesn’t have a plateau, phases 2 and 3 are combined

102
Q

The slope of phase 0 in SA node depolarization determines what?

A

How fast AP travel through the heart

103
Q

What is the conduction tissue in the R atrium called? What do they connect?

A

Internodal pathway (3) - anterior, middle, and posterior
Connect SA to AV node

104
Q

What is the conduction tissue called that is in the L atrium? Where does it come from?

A

Interatrial (Bachman’s) bundle - comes from the anterior nodal pathway from SA node

105
Q

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

A

0.03 sec

106
Q

How long does it take for the R atrium to depolarize?

A

0.07 sec

107
Q

How long does it take for the L atrium to depolarize? What does it signify on an ECG?

A

0.09 sec - P wave, both atria depolarized

108
Q

How long does it take for the entire heart to depolarize?

A

0.22 sec

109
Q

How long id the delay at the AV node?

A

0.12 sec -

110
Q

Why is there a delay at the AV node?

A

Gives atria time to contract before ventricles; also functions as a filter for electrical activity/extraneous AP (refractory period)
- caused by fat and less gap junctions in the AV node

111
Q

How long is the delay in the bundle of His?

A

0.01 sec

112
Q

How long does it take for an AP to get from the SA node to the interventricular branches?

A

0.16 sec - length of time before QRS interval starts

113
Q

The length of the QT interval corresponds to the AP of ________ tissue

A

endocardial ventricular tissue - start of depolarization of ventricles to repolarization

114
Q

The P wave is ____ boxes long by ___ boxes tall

A

2.5 x 2.5

115
Q

If the AP originated in the AV node instead of the SA node, what would change on the ECG?

A

The P wave would be inverted (negative deflection)

116
Q

How would hypertrophy of the R atrium change an ECG?

A

P wave taller

117
Q

How would hypertrophy of the L atrium change an ECG?

A

P wave longer

118
Q

A double hump of the P wave on an ECG would indicate an ______ block between the ______

A

electrical, atria

119
Q

How long is the QT interval?

A

0.25-0.35 sec

120
Q

How long is the PR interval?

A

0.16 sec

121
Q

How long is the QRS interval?

A

0.06 sec

122
Q

A longer and taller QRS interval would be caused by what?

A

extra ventricular tissue

123
Q

What would cause the QRS interval to be longer without it being taller?

A

Dilated cardiomyopathy

124
Q

_____ is the point at the end of the QRS complex that indicates that all of the ventricular tissue is depolarized

A

J point or isoelectric point

125
Q

You can compare the ____ to the point after the ___ wave to determine if there is an injury to the heart

A

J point to the point just after the T wave - ST segment

126
Q

An action potential that is transmitted in the relative refractory period will be _____

A

abnormal/weaker than normal AP

127
Q

A premature contraction affects what in the heart in terms of cardiac output

A

Decreased filling time (EDV) and therefore decreased Stroke volume. (overall decreased cardiac output)

128
Q

An impulse that is passed to the heart while it is in the absolute refractory period will result in ______

A

No contraction; no response from the cells that are in the absolute refractory period

129
Q

An early premature contraction begins in the ______ period

A

relative refractory period

130
Q

An early action potential that occurs after the refractory period is called ______ contraction. What will the effect be in the force of contraction?

A

later premature contraction
normal force of contraction

A&P 2024 (19 decks)

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