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USMLE Step 1 > Electrical Activity of Heart School Questions > Flashcards

Electrical Activity of Heart School Questions Flashcards

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USMLE® Step 1 flashcards
1
Q

Able to generate impulses

Membrane Potential is UNSTABLE

A

SA node

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2
Q

Period when ventricles are completely unexcitable

A

ARP

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3
Q

ARP Corresponds approximately to period of

A

Ventricular Repolarization

Ventricular Contraction

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4
Q

During ? period a new AP CANNOT be elicited

A

ARP

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5
Q

During ? period a new AP can be elicitied

A

Relative Refractory Period

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6
Q

“Tetany”, a period of constant contraction does not occur in Myocardium because ? is of each cell is LONG or SHORT

A

Refractory Period

Long

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7
Q

Natural Rate of Rhythmic Discharge is greated in?

A

SA node

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8
Q

Coronary Blood Flow is ? by activation of SNS

A

increased

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9
Q

Rate of Conduction of Purkinje Fibers is ? by activation of SNS

A

increased

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10
Q

What happens to slope of the Frank-sturling curve with INCREASED activation of the Frank Sterling Curve

A

Increased

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11
Q

Activation of SNS or PNS will INCREASE slope of Frank Sterling curve?

A

Increased

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12
Q

HR will ? with slowing of AP through AV node

A

Decrease HR

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13
Q

Dry mouth is sign of ? stimulation

A

SNS

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14
Q

Hypertension is sign of ? stimulation

A

SNS

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15
Q

Profuse Sweating is sign of ? stimulation

A

SNS

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16
Q

Slowing of the HR is sign of ? stimulation

A

Parasympathatic NS

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17
Q

Where is the Conduction Velocity slowed down?

A

AV node

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18
Q

The conduction Velocity of AV node

A

0.12 s

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19
Q

The conduction velocity in the in Purkinje Fibers is ______ , than in the AV node

A

Faster

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20
Q

Summation of Contractions (produce more contractions) can occur in Skeletal or Cardiac Muscle?

A

Skeletal

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21
Q

Summation of Contraction cannot occur in

A

Cardiac Myocytes

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22
Q

Absolute Refractory Period is longer in

A

Cardiac Myocytes

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23
Q

PHASE 0 AP change mediated by

A

Increased Membrane Permeability to Na

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24
Q

Phase 2 AP change mediated by

A

Voltage Gated Ca2+ ion channels

25
Q

Depolarization phase of AP mediated by

A

Voltage Gated Na+ ion channels open

26
Q

Prolonged period of Slow Repolarization

A

Plateau Phase

27
Q

Prolonged Depolarization is due to ? remaining open

A

Ca2+ channels

28
Q

Unlike other Cardiac Muscle, the entry of ? into PACEMAKER CELLS, is responsible for depolarization phase of AP

A

CA2+

29
Q

Increased Extracellular Ca 2+ causes :
____ contractility
____ HR

A

Increased Contraction

Increased HR

30
Q

Proper Sequence of Cardiac Excitation Ending

A

Bundle of His –> Purkinje Fibers

31
Q

the only point of contact between the Atria and Ventricles is

A

AV node

32
Q

Chambers in which Purkinje Fibers Distribution the AP

A

Both Ventricles

33
Q

Factors which decreased the contractility of the heart are known as

A

Negative Inotropic

34
Q

If membrane potential moves towards 0, because of Ionic concentrations ?

one wide contractility will

A

Decrease?

35
Q

Spontaneous depolarization is caused be

Efflux of

A

Efflux of K+

36
Q

Membrane potentials in proper sequence

A 
Threshold Voltage
Na+ Open
K+ open
Na Close
Membrane Depolarization
K+ close
37
Q

Low resistance pathways between myocardial cells that allow for the spread of action potentials are

A

Gap junctions

38
Q

Main Difference between Excitation-Contraction Coupling in Skeletal and Cardiac Muscle is

A

Entry of small amt of Ca2+ from ECF is essential for CARDIAC CONTRACTION

39
Q

Entry of small art of Ca2+ from ECF is essential for

A

Cardiac Contraction

40
Q

Spread of cardiac excitation between contracting cells is ensured by

A

Gap Junctions

Desmosomes

41
Q

The ECG is a recording of a
single cell point in time
single AP

true or false

A

FALSE

42
Q

During which phase of ECG shown are both atria depolarized

A

a (first segment)

43
Q

During which phase of ECG show

Depolarization of Ventricles

A

B-C-D (Second segment, QRS)

44
Q

ECG - depolarization of Ventricles

A 
"e' 
T wave (last segment, opposite of A)
45
Q

Complete depolarization of atria and ventricles

A

T

46
Q

known name of wave

Depolarization of AV NODE

A

A

47
Q

ECG

AV node delay can be mostly seen in

A

P-Q Segment

48
Q

which wave is due to depolarization of ventricles?

true quesiton

A

T wave

49
Q

which wave is not visible on EKG form?

A

AV node depolarization

50
Q

wave

depolarization of R+L atria

A

P wave

51
Q

? ekg for tiem to traverse atria——->purkinje cells

A

P-R interval

52
Q

QRS complex represents

A

Depolarization of R+L ventricles

53
Q

repolarization of atria

A

QRS complex

54
Q

rEpolarization of ventricles

A

T wave

55
Q

absent p wave

A

Lack of SA node conductivity

56
Q

qrs complex is spread of excitation from ___complex thru the ____

A

AV node

Ventricles

57
Q

Reduced Ventricular Ejection fraction wave

A

T WAVE

58
Q

EKG, stimulation of the Sympathetic nervous system

A

shortens Q-T interval

USMLE Step 1 (5 decks)

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