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SEE/BOARD STUDY > AA APEX CARDIAC A&P > Flashcards

AA APEX CARDIAC A&P Flashcards

1
Q

Ventricular myocytes resting potential is

A

-90mV

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2
Q

K+ and resting membrane potential how does hypokalemia affect RMP

A

Decrease (think linear relationships)

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3
Q

RMP is primarily regulated by

A

Potassium

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4
Q

Threshold potential is

A

-70 mV

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5
Q

Threshold potential is primary regulated by

A

Calcium

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6
Q

Hypokalemia and threshold potential

A

Decreases

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7
Q

When does sodium increases?

A

When the voltage gated sodium channels open to response to depolarization.

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8
Q

What facilitates the WAVE Of depolarization throughout the heart?

A

GAP junctions (T-tubules for other skeletal )

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9
Q

Which one contain more mitochondira, skeletal myocytes or ventricular myocytes?

A

Ventricular myocytes.

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10
Q

Unlike skeletal muscles, What serve as low resistance pathway that help spread the cardiac action potential? other names

A

Tight junctions or GAP junctions or nexi

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11
Q

Similarity of skeletal muscles and ventricular myocytes?

A

both have actin and myosin filaments
Capable of contration
T tubules and the SR work to maintain Ca2+ homeostasis for contraction and relaxation.

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12
Q

Define automaticity?

A

Spontaneous generation of an action potential

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13
Q

Define excitability

A

Ability to respond to an electrical stimulus and firing an action potential

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14
Q

Conductance explain

A

Because ions are charged particles, they cant just pass through, they need a channel to cross. Open channel allow increase conductance, closed channel does the opposite.

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15
Q

What is the definition of RMP?

A

Difference between inside of the cell and the outside of the cell.

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16
Q

The inside of the cell is _________when compared to the outside

A

negative.

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17
Q

What are the 3 mechanisms RMP is established By?

A
  1. Chemical force
  2. Electrostatic counterforce
  3. Na/K+ ATPase
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18
Q

Threshold potential

A

The internal voltage at which the cell depolarizes, Once depolarization begins it cannot be stopped.

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19
Q

Hyperpolarization definition

A

Increase polarity between the inside and the outside of the cell.

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20
Q

Repolarization definition

A

When the MP go back to RMP after depolarization

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21
Q

The myocyte is permeable to

A

Potassium

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22
Q

Why is the inside of the cell negative?

A

The cell continuously leaks potassium, it loses positive charge. This is why the inside of the cell is negative and the outside becomes relatively positive. This is why K+ is the primary determinant of the resting membrane potential.

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23
Q

When serum K+ decreases RMP becomes more _____and myocytes is more ______to depolarization

A

Negative : resistant

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24
Q

When serum K+ increases RMP becomes more _____and myocytes is more ______to depolarization

A

Positive, easily

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25
Q

ATPase pumps

A

3 Na out, 2 K+ in (against their concentration gradient)

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26
Q

When RMP approaches threshold potential, what happens?

A

Voltage-gated sodium channels open and sodium conductance increases, this depolarizes the cells

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27
Q

What are the 2 main purposes of the Na/K+ pump?

A

Removes the Na+ that enters the cells during depolarization

It returns K+ that has left the cell during depolarization.

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28
Q

What kind of transport does the Na/K-ATPase utilizes?

A

active transport mechanism requires energy in the form of ATP.

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29
Q

Phase 0 to Phase 4 what ions goes in or out?

A 
Phase 0 = Sodium in 
Phase 1 = Chloride in 
Phase 2 = Calcium in 
Phase 3= Potassium out
Phase 4 = Sodium out
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30
Q

Cardiac Action potential there is a plateau phase why?

A

depolarization is prolonged , It gives the cardiac myocytes time to contract , so the heart has enough time to eject its SV.

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31
Q

Tissue with NO PLATEAU PHASE

A

SA node
AV node
Neural tissue.

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32
Q

Where is the Absolute refractory period ?

A

From phase 0 to end of phase 2

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33
Q

What ECG segment is the Absolute Refractory period?

A

QT interval.

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34
Q

Where is the Relative refractory period ?

A

End of T

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35
Q

Slope of the Phase O upstroke indicates what?

A

Conduction velocity

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36
Q

Initial repolarization is what phase?

A

Phase 1 , and its the inactivation of the Na+ Channels. Cells become slightly positive

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37
Q

Phase 1 ions movements

A

K+ out

Cl- in

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38
Q

Phase 2 what happens

A

activation of slow voltage-gated Ca+ channels counters loss of K+ ions to maintain the depolarized state

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39
Q

Phase 2 action on repolarization ? Prolongs what?

A

Delays repolarization

Absolute refractory period is prolonged

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40
Q

What is necessary for the heart’s pumping action

A

Sustained contraction .

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41
Q

Final repolarization is stage

A

3

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42
Q

What happens during stage 3

A

K+ channels open (delayed rectifier)

K+ leaves cell faster than Ca+ Enters –> repolarization

43
Q

Phase 4 Resting phase

A

K+ out

Na/ K-ATPase function

44
Q

What is the primary determinant of the Pacemaker’ s intrinsic heart rate?

A

The funny current ( I-f)

45
Q

What sets the rate of spontaneous phase 4 depolarization in the SA node?

A

The funny current (I-f)

46
Q

Conduction system action potential pathway

A

SA node –> Internodal tracts –> AV node –> Bundle of HIS–> Left and Right BB –> Purkinje fibers.

47
Q

What determines the HR?

A

It is a function of : intrinsic firing rate of the dominant pacemaker usually the SA node AND Autonomic tone.

48
Q

SA node intrinsic firing rate

A

70-80 (faster in the denervated heart)

49
Q

AV node intrinsic firing rate

A

40-60

50
Q

Purkinje fibers intrinsic firing rate

A

15-40

51
Q

Other name for SA node

A

Keith-Flack node

52
Q

What determines the intrinsic heart rate?

A

The rate of spontaneous phase 4 depolarization of the SA node.

53
Q

Are all the cells in the myocardium capable of automaticity?

A

yes, each cell type has its own rate of spontaneous depolarization.

54
Q

Which cells determine how often the heart depolarizes?

A

The cells with the fastest rate

55
Q

Each time the SA nodes firers what happens?

A

It depolarizes the rest of the conduction system as well as the cardiac myocytes. AFter the cardiac cycle is complete the SA node will be first to fire again

56
Q

If SA node can’t do the job as the heart’s dominant pacemaker?

A

The cells with highest rate of phase four spontaneous depolarization will assume the PM responsibility.

57
Q

What system modulates the HR?

A

ANS

58
Q

PNS tone is through _____nerve?

A

Vagus nerve (CN X)

59
Q

What nerve innervates the SA node?

A

Right vagus SA nodes

Left vagus AV node

60
Q

SNS tone is innervated by?

A

Cardiac accelerator fibers (T1-T4)

61
Q

What is the main difference between the action potential of the SA vs the AV nodes?

A

AV has a slower slope during phase 4 and a slower intrinsic firing rate.

62
Q

2 Main differences in the action potential morphology of the SA and AV nodes is that there is

A

NO plateau phase and RMP is HIGHER

63
Q

SA node: Phase 4 is the

A

Spontaneous depolarization

64
Q

What happens during the Phase 4 spontaneous depolarization of the SA node ?

A

The membrane is leaky to Na+

Na+ enters cell progressive making it more positive

65
Q

Ions movement during the Phase 4 spontaneous depolarization of the SA node ?

A

Na+ in (I-f==> funny current)

Ca2+ in (T-Type)

66
Q

Why is the funny current called that?

A

It is activated by hyperpolarization (not depolarization)

67
Q

At -50mV , what happens in the SA nodes

A

Transient Ca2+ channels, T-type open to further depolarize the cell.

68
Q

What happens during the Phase 0 spontaneous depolarization of the SA node ?

A

Ca2+ entry via voltage gated Ca2+ channels (L-type)–> depolarization.
Sodium and T-Type Ca2+ channels close.

69
Q

What happens during the Phase 3 spontaneous depolarization of the SA node ?

A

K+ Channels open
K+ leaves the cells, making the interior more negative
K+ efflux –> repolarization and the return to phase 4

70
Q

Repolarization of the SA node

A

Decrease Ca2+ conductance by closing L-type calcium channels.

71
Q

HR can be manipulated by manipulating 3 variables

A

a. Rate of Spontaneous phase 4 depolarization
b. Threshold potential
c. Resting membrane potential

72
Q

What are the 3 conditions that can increase the HR? HOw do they increase the HR?

A
  1. Rate of spontaneous phase 4 depolarization increases
  2. Rate of phase 4 remains constant, but threshold potential becomes MORE negative, shortens the distance between RMP and TP so the cells reach threshold faster
  3. Rate of phase 4 remains constant, but RMP becomes less negative. Also shortens the distance between RMP and TP , so the cells reach threshold faster
73
Q

SNS stimulation via NE does what?

A

increases HR by increasing Na+ and Ca2+ conductance. This increases the rate of spontaneous phase 4 depolarization

74
Q

PNS stimulation via Ach does what?

A

slow HR by INCREASING K+ conductance and HYPERPOLARIZING the SA node. this decreases RMP and reduces rate of spontaneous phase 4 depolarizations.

75
Q

CaO2 is

A

Arterial oxygen content

76
Q

What is a normal CaO2 for a 70kg adult?

A

20ml/O2/ dl

77
Q

What is a normal DO2 (oxygen delivery) for a 70kg adult?

A

1000ml/min

78
Q

What is a normal VO2 (oxygen consumption) for a 70kg adult?

A

250 ml/min

79
Q

What CvO2 ?

A

Venous oxygen content

80
Q

Normal CvO2 for 70 kg adult ?

A

15ml/dl

81
Q

What is the formula of DO2?

A

DO2 = CO x [(Hgb x SaO2 x 1.34) + (PaO2 x 0.003)] x 10

82
Q

The essence of DO2, we need to ask 2 questions:

A

How much O2 is in the blood

How fast is the O2 being delivered to the tissues.

83
Q

The normal O2 extraction is

A

250ml/min (whole body O2 extraction ratio is 25%)

84
Q

Normal CO is

A

5-6L/min

85
Q

Changes in body temperature and viscosity= increase temp

A

increased temp = Decrease viscosity and increase flow

86
Q

Changes in body temperature and viscosity= decrease temp

A

decreased temp = Increase viscosity and decrease flow

87
Q

Changes in Hematocrit increase Hct

A

Increase viscosity and decreased flow

88
Q

Changes in Hematocrit Decrease Hct

A

Decrease viscosity and increased flow.

89
Q

Therefore, as HCT increases, blood flow

A

decreases

90
Q

What law forms the basis for understanding hemodynamics?

A

Ohm’s law

91
Q

Current=

A

Voltage Difference/ resistance

92
Q

Flow

A

Pressure Gradient / Resistance

93
Q

MAP

A

CO x SVR / 80 + CVP

94
Q

Poiseuille’s Law

A

Q = Pi R^4 Delta P / 8 n l

95
Q

Doubling the radius and flow

A

Increase flow by 16 fold, tripling the radius increase flow by 81-fold.

96
Q

3 types of flow

A

Laminar
Turbulent
Transitional

97
Q

Describe the laminar flow?

A

Molecules travel in a parallel path through the tube

98
Q

Describe the turbulent flow?

A

Moleculte travel in a non-linear path

99
Q

Describe transitional flow

A

Laminar flow along the vessels walls with turbulent in the center.

100
Q

Re < 2000

A

Predicts that flow will be mostly laminar

101
Q

Re > 4000

A

Predicts that flow

102
Q

What is used to predict flow?

A

Reynolds number (Re)

103
Q

Re 2000-4000

A

Suggest transitional flow

104
Q

When flow is turbulent, what happens to energy?

A

lost via heat and vibration . Pressure gradient will be larger than what is predicted by poiseuille’s law

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