Cardiac Muscle - Quiz 1 Flashcards

1
Q

other names for cardiac muscle cell

A
  • cardiac myocyte

- cardiac muscle fiber

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2
Q

cardiac muscle cells contain

A
  • actin
  • myosin
  • troponin
  • tropomyosin
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3
Q

cardiac muscle cells are connected to one another by

A
  • intercalated discs
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4
Q

intercalated discs contain

A
  • desmosomes
  • gap junctions
  • fasciae adherentes (in transverse portion)
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5
Q

intercalated discs contain desmosomes for

A
  • strength
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6
Q

intercalated discs contain gap junctions for

A
  • low resistance pathways for action potential spread through atria and ventricles
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7
Q

Gap junctions connect

A
  • atrial myocytes with other atrial myocytes

- ventricular myocytes with other ventricular myocytes

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8
Q

are atrial myocytes connected to ventricular myocytes

  • why?
A
  • no

- allows time for ventricles to fill

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9
Q

role of nodal and conducting cardiac cells

A
  • set electrical rhythm

- make sure electrical spread happens in orderly and regulated fashion

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10
Q

which cardiac myocyte has the fastest spontaneous firing

A
  • SA node
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11
Q

electrical coupling between cardiac cells occurs through

A
  • intercalated discs

- gap junctions

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12
Q

electrical coupling between cardiac cells allows for

A
  • synchronized spread of depolarization
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13
Q

what initiates the action potential

A
  • SA node
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14
Q

what is the SA node also known as

A
  • normal pacemaker
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15
Q

control of SA node

A
  • autonomous
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16
Q

external stimulus of SA node

A
  • no external stimulus needed
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17
Q

spread of action potential pathway

A
  • SA node
  • internodal tracts
  • AV node
  • common bundle of His
  • left and right bundle branches
  • purkinje fibers
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18
Q

internodal tracts help spread action potential to

A
  • atria
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19
Q

atrial depolarization results in

A
  • atrial contraction
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20
Q

contraction of atria occurs

A
  • nearly simultaneously
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21
Q

atria connection to ventricles

A
  • electrically insulated from ventricles

- except at AV node

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22
Q

what is the path for excitation from the atria to the ventricles

A
  • AV node
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23
Q

speed of AV nodal cells conducting action potential

A
  • slow
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24
Q

slow conduction of action potentials by AV node allows for

A
  • a delay between atrial and ventricular contraction

- allows more time for ventricle to fill with blood

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25
Q

what occurs after ventricular depolarization

A
  • ventricular contraction
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26
Q

where does contraction start in the ventricles

A
  • starts in the apex then spreads to ventricle walls
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27
Q

coordination of contraction of two ventricles

A
  • contract almost simultaneously
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28
Q

action potential between heartbeats

A
  • no action potentials

- pacemaker cells are depolarizing

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29
Q

action potentials of myocytes from different regions of the heart

A
  • have different action potentials
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30
Q

phase 4 ventricular myocytes action potential

A
  • resting membrane potential
31
Q

phase 0 ventricular myocytes action potential

A
  • rapid depolarization
32
Q

phase 1 ventricular myocyte action potential

A
  • partial repolarization
33
Q

phase 2 ventricular myocytes action potential

A
  • plateau
34
Q

plase 3 ventricular myocyte action potenial

A
  • rapid repolarization
35
Q

channels in phase 4 of ventricular myocyte action potenial

A
  • very leaky IR K channels open
36
Q

channels in phase 0 of ventricular myocyte action potenial

A
  • voltage gated NA+ channels open

- IR K channels blocked

37
Q

channels in phase 1 of ventricular myocyte action potenial

A
  • transient outward K channels open
  • voltage gated L-type Ca channels (DHP receptors) begin to open
  • voltage gated Na channels inactivating
38
Q

channels in phase 2 of ventricular myocyte action potenial

A
  • voltage gated L-type Ca channels (DHP receptors) open
  • DR K channels opening
  • transient outward K channels inactivating
  • voltage gated Na+ channels inactivated
39
Q

channels in phase 3 of ventricular myocyte action potenial

A
  • voltage gated L-type Ca channels (DHP receptors) inactivating
  • DR K+ open
  • transient outward K+ channels inactivated
40
Q

atrial, purkinje, and ventricular cells action potential phase 0 - threshold

A
  • around -75 mv
41
Q

atrial, purkinje, and ventricular cells action potential phase 0 - current

A
  • Na+ current
42
Q

atrial, purkinje, and ventricular cells action potential phase 0 - channels

A
  • voltage-gated Na+ channels
43
Q

atrial, purkinje, and ventricular cells action potential - conduction rates

A
  • high conduction rates
44
Q

atrial, purkinje, and ventricular cells action potential phase 0 called

A
  • upstroke
45
Q

atrial, purkinje, and ventricular cells action potential phases 1 and 2 called

A
  • depolarization
46
Q

atrial, purkinje, and ventricular cells action potential phases 1 and 2 - channels

A
  • Na+ channels inactivate

- Ca and K channels activate

47
Q

atrial, purkinje, and ventricular cells action potential phase 3 called

A
  • repolarization
48
Q

atrial, purkinje, and ventricular cells action potential phase 3 - channels

A
  • Ca2+ channels inactivate

- K+ channels continue to open

49
Q

excitation contraction coupling begins with

A
  • membrane depolarized by Na+ entry as action potential begins
50
Q

excitation contraction coupling - depolarization causes

A
  • opening of L-type Ca2+ channels in T-tubules
51
Q

excitation contraction coupling - opening of Ca2+ channels causes

A
  • trigger Ca2+ enters cytosol contributing to cell depolarization
  • trigger Ca2+ binds to and open ryanodine receptor calcium channels in the SR
52
Q

excitation contraction coupling - after Ca2+ has been released from the SR

A
  • Ca2+ flows into the cytosol

- raises Ca2+ concentration

53
Q

excitation contraction coupling - what does Ca2+ bind to

A
  • binds to troponin

- exposes cross-bridge binding sites on thin filaments

54
Q

excitation contraction coupling - bindings of calcium to troponin causes

A
  • cross bridge cycling
  • force generation
  • sliding of thick and thin filaments
55
Q

excitation contraction coupling - how does Ca2+ get out of the cell

A
  • Ca2+-ATPase pumps return Ca2+ to SR

- Na+/Ca2+ exchangers remove Ca2+ from cell

56
Q

excitation contraction coupling - when is the membrane repolarized

A
  • when K+ exits to end the action potential
57
Q

channels in SA node action potentials

A
  • K+ channels
  • L-type Ca2+ channels
  • HCN channels
  • T-type Ca2+ channels
58
Q

K+ channels in SA node action potentials

A
  • IR K channels

- DR K channels

59
Q

HCN channels in SA node action potentials permeable to

A
  • both Na+ and K+
60
Q

HCN channels in SA node action potentials open at

A
  • negative membrane potentials
61
Q

HCN channels in SA node action potentials close when

A
  • as membrane depolarizes
62
Q

HCN channels in SA node action potentials - current called

A
  • I_f
63
Q

HCN channels in SA node action potentials - sensitive to

A
  • NE

- EPI

64
Q

T-Type Ca+ channels length of opening

  • open when
A
  • transient

- open only briefly at negative voltages -50 then close

65
Q

cardiac action potentials of SA and AV node - resting membrane potential

A
  • no resting membrane potential
66
Q

cardiac action potentials of SA and AV node phase 0

A
  • upstroke
67
Q

cardiac action potentials of SA and AV node phase 0 upstroke due to

A
  • Ca2+ current
  • T-type Ca2+ channels first
  • then L-type Ca2+ channels
68
Q

cardiac action potentials of SA and AV node phase 0 - threshold

A
  • higher threshold

- slower

69
Q

cardiac action potentials of SA and AV node phases 1 and 2

A
  • no phases 1 or 2
70
Q

cardiac action potentials of SA and AV node phase 3 - current

A
  • DR K-current begins quickly then decreases
71
Q

cardiac action potentials of SA and AV node phase 4

A
  • slow depolarization
72
Q

cardiac action potentials of SA and AV node phase 4 - currents

A
  • IR K+ currents open then decrease

- Ca2+ and I_f currents increase

73
Q

which has the slowest spontaneous firing rate

A
  • ventricular myocyte