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76 notecards = 19 pages (4 cards per page)

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18.5 Pacemaker Cells

front 1

pacemaker cells contract

back 1

false

front 2

the sponteneously produced action is called

back 2

autorhythmic

front 3

where are pacemaker cells located?

back 3

throughout heart along special conduction pathways

front 4

what spreads the depolarizing current to cardiac muscle cells

back 4

gap junctions

front 5

pacemaker cells have an unstable resting membrane potential

back 5

true

front 6

the resting membrane potential of pacemaker cells is what?

back 6

-60 mV

front 7

pacemaker cells close K+ channels and open Na+ slowly to let sodium in

back 7

true

front 8

the cell become slowly depolarized by the Na+ voltage channels opening

back 8

true

front 9

the threshold of pacemaker cells is what?

back 9

-40mV

front 10

at the threshold what voltage gated channel opens?

back 10

Ca2+

front 11

for pacemakers to repolarize what is opened?

back 11

K+ voltage gated channels

front 12

conduction pathways run throughout the myocardium

back 12

true

front 13

what initiates the heart beat

back 13

the SA node

front 14

SA node

back 14

sinoatrial node

front 15

where are the SA nodes?

back 15

small mass of pacemaker cells in right atrial wall; inferior to the superior vena cava

front 16

how many impulses does the SA node generate a minute

back 16

75

front 17

The SA node generates a faster impulse than any other heart cell

back 17

true

front 18

the SA node is the true pacemaker of the heart

back 18

true

front 19

what does the Bachmann's bundle connect?

back 19

the right and left atria

front 20

the bachmann's bundle keeps both atria at synch

back 20

true

front 21

depolarization of the SA node causes what to happen?

back 21

atria to contract at the same time

front 22

there are gap junctions between atrial and ventricular myocardium

back 22

false

front 23

what does the internodal pathways connect?

back 23

SA node to AV node

front 24

where is the AV node located

back 24

in the interatrial septum, near tricuspid

front 25

What does the AV node do?

back 25

delays depolarization

front 26

AV node

back 26

atrioventricular node

front 27

how many impulses does the AV node generate per minute?

back 27

50

front 28

the AV node cannot run the heart if the SA is damages

back 28

false

front 29

the atrioventricular bundle connects what

back 29

AV node to ventricles

front 30

bundle of His

back 30

atrioventricular bundle

front 31

what is the only electrical connection between the atria and the ventricles?

back 31

atrioventricular bundle

front 32

atrioventricular bundle splits into right and left bundle branches

back 32

true

front 33

atrioventricular bundle does not continue on to form Purkinje fibers

back 33

false

front 34

purkinje fibers

back 34

depolarize the contractile cells of ventricles

front 35

subendocardial conducting network

back 35

purkinje fibers

front 36

purkinje fibers innervate papillary muscles

back 36

true

front 37

depolarization of pacemaker cells cause depolarilzation of cardiac muscles cells

back 37

true

front 38

what is the resting membrane potential in contractile cells

back 38

-90 mV

front 39

in resting membrane potential in contractile cells what channel is always open?

back 39

K+

front 40

what is the resting membrane potential for skeletal muscle?

back 40

-90 mV

front 41

during depolarization of contractile cells what is opened?

back 41

voltage gates fast Na+ channels, Na rapidly flow into cell

front 42

sarcolemma depolarizes to +30mV

back 42

true

front 43

at +30mV what opens in contractile cells?

back 43

voltaged gates slow Ca2+ channels

front 44

during repolarization of contractile cells what is opened?

back 44

voltage gated K+ channels and K+ leaves the cell

front 45

absolute refractory period

back 45

time when cell cannot depolarize again

front 46

the absolute refractory period is longer in cardiac muscle than skeletal muscle

back 46

true

front 47

the absolute refractory period prevents tetanic contractions such as cramps, spasms, and tremors

back 47

true

front 48

hypercalcemia

back 48

too much calcium

front 49

what does hypercalcemia cause?

back 49

prolonged and spastic heart contractions

front 50

hypocalcemia

back 50

low calcium levels

front 51

hypocalcemia reduces what?

back 51

the force of each heartbeat

front 52

hyperkalemia

back 52

high potassium levels

front 53

what does hyperkalemia do?

back 53

speeds up membrane repolarization disrupting heart rhythm

front 54

hypernatremia

back 54

blood Na+ levels are too high

front 55

what does hypernatremia prevent

back 55

the entry of calcium into myocardium

front 56

arrhythmia is a heart defect

back 56

true

front 57

arrhythmia

back 57

uncoordinated atrial and ventricular contraction

front 58

two types of arrhythmia

back 58

PAT and V-tac

front 59

PAT

back 59

paroxysmal atrial tachycardia; burst of atrial contractions

front 60

V-tac

back 60

ventricular tachycardia; rapid uncoordinated ventricular contractions

front 61

fibrillation

back 61

rapid and irregular contractions of cardiac muscles

front 62

what can treat fibrillation

back 62

defibrillator

front 63

what can lead to fibrillation

back 63

tachycardia

front 64

defibrillation does what?

back 64

restart entire electrical systems

front 65

ectopic focus

back 65

inappropriate region of heart controls rhythm

front 66

where can ectopic focuses appear

back 66

atria or ventricles

front 67

what are ectopic focuses caused by

back 67

  • ischemic damage to conduction pathways
  • stimulants
  • fever

front 68

what can ectopic focuses lead to

back 68

arrhythmia and fibrillation

front 69

a heart block is damage to what structure in the heart ?

back 69

AV node or AV bundle

front 70

first degree heart block

back 70

depolarization is delayed for too long

front 71

second degree heart block

back 71

only some of the impulses are transmitted

front 72

third degree heart block

back 72

no action potential pass to the ventricles

front 73

third degree heart block aka

back 73

complete heart block

front 74

asystole

back 74

period when heart fails to contract

front 75

asystole is when there are electrical signals from cardiac muscles

back 75

false

front 76

flatline

back 76

asystole