Cardiac Physiology

Question 1

resting membrane potential of cardiac muscle?

Answer 1

-85 to -95 mV

Question 2

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

Answer 2

longer

Question 3

what occurs during ventricular muscle action potential phase 0?

Answer 3

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

Question 4

what occurs during ventricular muscle action potential phase 1?

Answer 4

transient opening of K+ channels

Question 5

what occurs during ventricular muscle action potential phase 3?

Answer 5

K+ channels open up more, causing repolarization

Question 6

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

Answer 6

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

Question 7

what kickstarts the ventricular muscle action potential?

Answer 7

pacemaker cells

Question 8

what electrical activity must occur before ventricular contraction can occur?

Answer 8

ventricular depolarization

Question 9

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

Answer 9

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

Question 10

SV= ____________ - ________________

Answer 10

SV= EDV-ESV

Question 11

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

Answer 11

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

Question 12

what is a normal ejection fraction?

Answer 12

60%

Question 13

aortic and mitral normal valve area?

Answer 13

2.5-3.5 cm2

Question 14

pulmonic normal valve area?

Answer 14

4-6 cm2

Question 15

tricuspid normal valve area

Answer 15

8-10 cm2

Question 16

normal pressure of right atrium

Answer 16

0-6 mmHg

Question 17

normal pressure of right ventricle during diastole and systole

Answer 17

0-6/15-30 mmHg

Question 18

normal pressure of pulmonary artery during diastole and systole

Answer 18

6-12/15-30 mmHg

Question 19

normal pressure of left atrium

Answer 19

6-12 mmHg

Question 20

normal pressure of left ventricle during diastole and systole

Answer 20

6-12/100-140 mmHg

Question 21

normal pressure of aorta during diastole and systole

Answer 21

60-80/100-140 mmHg

Question 22

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

Answer 22

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

Question 23

increased preload effects on EDV and SV?

Answer 23

it will increase EDV, which in turn increases SV

Question 24

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

Answer 24

allows atria to contract before ventricles

Question 24

vagal fibers primarily go to what area of the heart?

Answer 24

atria

Question 25

what is overdrive suppression?

Answer 25

When faster pacemakers suppress the activity of slower pacemakers

Question 25

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

Answer 25

positive

Question 26

what is an ectopic pacemaker?

Answer 26

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

Question 26

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

Answer 26

300 bpm

Question 27

common causes of conduction block?

Answer 27

cardiac hypertrophy purkinje system block

Question 27

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

Answer 27

negative

Question 27

classical "rabbit ear" pattern is seen with what arythmia?

Answer 27

RBBB>LBBB

Question 28

hyperkalemia can lead to right or left axis deviation?

Answer 28

left

Question 28

cessation of P waves is seen in what block?

Answer 28

sinoatrial block

Question 29

digoxin works by?

Answer 29

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

Question 30

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

Answer 30

0.2 seconds

Question 30

normal P-R interval

Answer 30

0.16 seconds

Question 31

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

Answer 31

atria beat faster than the ventricles

Question 31

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

Answer 31

0.25 to 0.45 seconds

Question 31

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

Answer 31

Second degree: Mobitz Type I (Wenckebach)

Question 31

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

Answer 31

second degree: Mobitz Type II

Question 32

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

Answer 32

no relationship. each have their own rate setting pacemaker

Question 32

relationship to third degree AV block and overdrive suppression?

Answer 32

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

Question 33

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?

Answer 33

Stokes-Adams syndrome overdrive suppression

Question 34

the cause of premature contractions?

Answer 34

ectopic foci in the heart

Question 34

3 causes of ectopic foci?

Answer 34

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

Question 35

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

Answer 35

phase 3 blocks K+ channels, delaying repolarization

Question 36

key characteristic of impulse during premature contractions?

Answer 36

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

Question 37

conduction abnormality in PVC's

Answer 37

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

Question 38

Long QT syndrome is related to what electrolyte deficiencies?

Answer 38

hypomagnesium and hypokalemia

Question 39

most frequent cause of a-fib?

Answer 39

atrial enlargement due to A-V valve dysfunction

Question 39

what can cause circus movements?

Answer 39

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

Question 39

atrial rate compared to ventricular rate in A-flutter?

Answer 39

atria beat 2-3x faster

Question 40

AV node rate

Answer 40

40-60 bpm

Question 40

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

Answer 40

decrease in SV

Question 40

and increase in SVR will have what effect on ESV?

Answer 40

increase in ESV

Question 41

purkinje fibers rate

Answer 41

15-40 bpm

Question 42

conduction time at AV node

Answer 42

0.03 seconds

Question 43

conduction time at purkinje fibers

Answer 43

0.12 seconds

Question 44

p wave represents what?

Answer 44

atrial depolarization in response to SA node triggering

Question 45

PR interval represents what?

Answer 45

AV nodal delay to allow ventricular filling

Question 46

ST segment represents what?

Answer 46

beginning of ventricular repolarization

Question 46

QRS complex represents what?

Answer 46

ventricular depolarization

Question 47

T-wave represents what?

Answer 47

ventricular repolarization

Question 48

HR seen in carotid syndrome

Answer 48

bradycardia

Question 49

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

Answer 49

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

Question 50

A-fib effects on ventricular efficiency?

Answer 50

decreased by 20-30%