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pathophysiology II > Cardiac Physiology > Flashcards

Cardiac Physiology Flashcards

1
Q

resting membrane potential of cardiac muscle?

A

-85 to -95 mV

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2
Q

the plateau of cardiac muscle action potential is longer or shorter than skeletal muscle?

A

longer

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3
Q

what occurs during ventricular muscle action potential phase 0?

A

fast Na+ channels open first, then slow Ca2+ open before peak

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4
Q

what occurs during ventricular muscle action potential phase 1?

A

transient opening of K+ channels

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5
Q

what occurs during ventricular muscle action potential phase 3?

A

K+ channels open up more, causing repolarization

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6
Q

What occurs during ventricular muscle action potential phase 2? what is unique about this phase?

A

Ca2+ open more, in balance with K+
this causes the unique plateau seen in ventricular muscle action potential

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7
Q

what kickstarts the ventricular muscle action potential?

A

pacemaker cells

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8
Q

what electrical activity must occur before ventricular contraction can occur?

A

ventricular depolarization

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9
Q

how does blood still leave the ventricles if pressure is higher in the aorta at the later part of the ejection phase?

A

the blood leaving the ventricles has greater kinetic energy than that in the aorta

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10
Q

SV= ____________ - ________________

A

SV= EDV-ESV

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11
Q

what causes the notch (incisura) seen on an aortic pressure curve?

A

sudden cessation of back flow from aorta into the ventricles due to the aortic valve closure

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12
Q

what is a normal ejection fraction?

A

60%

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13
Q

aortic and mitral normal valve area?

A

2.5-3.5 cm2

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14
Q

pulmonic normal valve area?

A

4-6 cm2

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15
Q

tricuspid normal valve area

A

8-10 cm2

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16
Q

normal pressure of right atrium

A

0-6 mmHg

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17
Q

normal pressure of right ventricle during diastole and systole

A

0-6/15-30 mmHg

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18
Q

normal pressure of pulmonary artery during diastole and systole

A

6-12/15-30 mmHg

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19
Q

normal pressure of left atrium

A

6-12 mmHg

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20
Q

normal pressure of left ventricle during diastole and systole

A

6-12/100-140 mmHg

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21
Q

normal pressure of aorta during diastole and systole

A

60-80/100-140 mmHg

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22
Q

isovolumetric contraction of the left ventricle begins and ends at what two valvular actions?

A

begins when the mitral valve closes
ends with the opening of the aortic valve

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23
Q

increased preload effects on EDV and SV?

A

it will increase EDV, which in turn increases SV

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24
Q

importance of the delay in impulse between the AV node and bundle of His?

A

allows atria to contract before ventricles

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24
Q

vagal fibers primarily go to what area of the heart?

A

atria

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25
Q

what is overdrive suppression?

A

When faster pacemakers suppress the activity of slower pacemakers

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25
Q

a wave of depolarization toward the recording electrode would result in a ____________ deflection

A

positive

26
Q

what is an ectopic pacemaker?

A

Is an excitable group of cells that causes a premature heart beat outside the normally functioning SA node of the human heart. also occurs during an A-V block

26
Q

if R waves are seperated by one large box, then what would the rate be?

A

300 bpm

27
Q

common causes of conduction block?

A

cardiac hypertrophy
purkinje system block

27
Q

a wave of depolarization away from the recording electrode would result in a _____________ deflection

A

negative

27
Q

classical “rabbit ear” pattern is seen with what arythmia?

A

RBBB>LBBB

28
Q

hyperkalemia can lead to right or left axis deviation?

A

left

28
Q

cessation of P waves is seen in what block?

A

sinoatrial block

29
Q

digoxin works by?

A

Inhibiting Na k ATPase, leading to prolonged depolarization of the atria and slowing conduction through A-V node

30
Q

a P-R interval > than _____________ seconds indicates a first degree block

A

0.2 seconds

30
Q

normal P-R interval

A

0.16 seconds

31
Q

relationship between the atria and ventricles in second degree incomplete block?

A

atria beat faster than the ventricles

31
Q

a P-R interval from ____________ to __________ indicates a second degree block

A

0.25 to 0.45 seconds

31
Q

gradually lengthening PR interval until reaching a conduction block occurs in what type of AV block?

A

Second degree: Mobitz Type I (Wenckebach)

31
Q

which type of AV block has a fixed PR interval of either 3:2 or 2:1

A

second degree: Mobitz Type II

32
Q

relationship between the ventricles and atria in third degree AV block?

A

no relationship. each have their own rate setting pacemaker

32
Q

relationship to third degree AV block and overdrive suppression?

A

there is not conduction through AV node, causing the ventricles to rely on overdrive suppression of a pacemaker further down the conduction pathway

33
Q

syndrome in which a complete AV block comes and goes, leading to fainting d/t cessation of ventricles for 5-30 seconds? what causes the cessation of the ventricles?

A

Stokes-Adams syndrome
overdrive suppression

34
Q

the cause of premature contractions?

A

ectopic foci in the heart

34
Q

3 causes of ectopic foci?

A

-local areas of ishcemia
-calcified plaque
-toxic irritation of AV node, purkinje fibers, or myocardium by drugs, nicotine, or caffeine

35
Q

what phase of ventricular action potential does amiodarone work on? what is the mechanism?

A

phase 3
blocks K+ channels, delaying repolarization

36
Q

key characteristic of impulse during premature contractions?

A

the impulse travels backwards into the atria from AV node/bundle to the SA node

37
Q

conduction abnormality in PVC’s

A

area that depolarizes first also repolarizes first (opposite of normal)

38
Q

Long QT syndrome is related to what electrolyte deficiencies?

A

hypomagnesium and hypokalemia

39
Q

most frequent cause of a-fib?

A

atrial enlargement due to A-V valve dysfunction

39
Q

what can cause circus movements?

A

-long pathway (dilated heart)
-decreased conduction velocity (Purkinje block, ischemia, high K+)
-shortened refractory period (epinephrine)

39
Q

atrial rate compared to ventricular rate in A-flutter?

A

atria beat 2-3x faster

40
Q

AV node rate

A

40-60 bpm

40
Q

an increase in end systolic volume will have what effect on SV?

A

decrease in SV

40
Q

and increase in SVR will have what effect on ESV?

A

increase in ESV

41
Q

purkinje fibers rate

A

15-40 bpm

42
Q

conduction time at AV node

A

0.03 seconds

43
Q

conduction time at purkinje fibers

A

0.12 seconds

44
Q

p wave represents what?

A

atrial depolarization in response to SA node triggering

45
Q

PR interval represents what?

A

AV nodal delay to allow ventricular filling

46
Q

ST segment represents what?

A

beginning of ventricular repolarization

46
Q

QRS complex represents what?

A

ventricular depolarization

47
Q

T-wave represents what?

A

ventricular repolarization

48
Q

HR seen in carotid syndrome

A

bradycardia

49
Q

Incomplete Intraventricular Block (Electrical Alternans) is related to an issue with what part of the conduction pathway?

A

peripheral portions of the purkinje fibers work some of the time, resulting in abnormal QRS waves

50
Q

A-fib effects on ventricular efficiency?

A

decreased by 20-30%

pathophysiology II (3 decks)

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