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cardiovascular system > Electrical Activity of the Heart > Flashcards

Electrical Activity of the Heart Flashcards

1
Q

what is contraction of heart muscle stimulated by?

A

excitation contracting coupling

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2
Q

what is A?

A

T-tubule

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3
Q

what is B?

A

Actin

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4
Q

what is C?

A

myosin

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5
Q

what is D?

A

z-line

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6
Q

what is the process of a normal muscle contraction?

A
  1. action potential reaches cell and causes Na voltage channels to open
  2. cell depolarises and causes calcium to be released from sarcoplasmic reticulum
  3. calcium binds to troponin and starts the muscle contraction
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7
Q

where is actin anchored?

A

z line

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8
Q

what are T-tubules?

A

deep invaginations in the muscle membrane that interact with the organelles in the cell, such as the sarcoplasmic reticulum

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9
Q

what allows cardiac cells to act as one big cell?

A

intercalated disks

  • gap junctions (electrical connection): allow cells to communicate to each other by using signalling molecules
  • desmosomes (physical connection): prevent cells from separating during contraction
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10
Q

what are intercalated discs?

A

connect cardiac cells to allow them to work as a single functional organ

  • gap junctions
  • desmosomes
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11
Q

what are the differences between the action potentials of skeletal muscle and cardiac muscle?

A

action potential lasts for way longer in cardiac muscle

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12
Q

how long does the action potential last for in skeletal muscle and cardiac muscle?

A

2ms in skeletal muscle

250ms in cardiac muscle

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13
Q

what does the action potential lasting for ages in a cardiac cell allow?

A

calcium to enter from outside the cell as well as sodium, allowing regulation of contraction

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14
Q

what does the longer action potential allowing calcium and sodium to enter from outside the cell allow?

A

heart contraction to be stronger or weaker

refractory period is longer

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15
Q

which is cardiac and skeletal muscle has the longer refractory period?

A

cardiac muscle

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16
Q

what differences are there between cardiac and skeletal muscle due to cardiac muscle having a longer refractory period?

A

skeletal muscle contractions can add together and accumulate (tetanus) due to many action potentials being added to one another

cardiac muscle has to fully contract before it can be stimulated again and so they do not add onto each other

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17
Q

why is it important that the long refractory period of cardiac muscle mean tetanus cannot occur?

A

heart needs to fully contract and then relax to pump blood

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18
Q

what is tetanus?

A

sustained muscle contraction evoked when the motor nerve that innervates a skeletal muscle emits action potentials at a high rate

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19
Q

what do cardiac cells that have unstable resting membrane potentials act as?

A

pacemakers

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20
Q

what does having pacemakers allow a cell to do?

A

depolarise again quicker

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21
Q

is there a greater K+ concentration inside or outside the cell

A

inside

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22
Q

is there a greater Na+ concentration inside or outside the cell?

A

outside

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23
Q

is there a greater Ca2+ concentration inside or outside the cell?

A

Outside

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24
Q

what causes the resting membrane potential of a cell?

A

at rest K+ gated channels are open (leaky) which makes the cell more negative until equilbrium is rached at -90mV

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25
Q

what is the resting membrane potential (RMP) of cardiac muscle?

A

-90mV

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26
Q

what is the process of non-pacemaker action potential?

A
  1. resting membrane potential (high resting permeability to K+
  2. initial depolarisation (increase in permeability to Na+)
  3. plateau (increase in permeability to Ca2+, L-type, and decrease in permeability to K+)
  4. repolarisation (decrease in permeability to Ca2+ and increase in permeability to K+)
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27
Q

what causes the resting membrane potential in non-pacemaker cells?

A

high resting permeability to K+

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28
Q

what causes the initial depolarisation in non-pacemaker cells?

A

increase in permeability to Na+

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29
Q

what causes the plateau in non-pacemaker action potentials?

A

increase in permeability to Ca2+ (L-type)

decrease in permeability to K+

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30
Q

what causes the repolarisation of non-pacemaker action potential?

A

decrease in permeability to Ca2+

increase the permeability to K+

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31
Q

what are the 2 different kinds of calcium channels?

A

L-type

T-type

32
Q

do L-type or T-type calcium channels let lots of calcium in?

33
Q

what cause the pacemaker potential (pre-potential) in a pacemaker action potential?

A

gradual decrease in permeability to K+

early increase in permeability to Na+

late increase in permeability to Ca2+ (T-type)

34
Q

what causes the action potential in the pacemaker action potential?

A

increase in permeability to Ca2+ (L-type)

35
Q

what does the pacemaker action potential of the heart explain?

A

autorhythmicity

36
Q

what brings heart cells to action potential in the first place?

A

pacemaker action potential

37
Q

how would you describe the difference between pacemaker and non-pacemaker cells?

A

not black and white, it is a spectrum

38
Q

what is the pacemaker cell of the heart?

A

the one with the fastest rhythm, all cells around it take up this rhythm

39
Q

what can electrical activity be modulated by?

A
  • sympathetic and parasympathetic systems
  • drugs
  • temperature
  • hyperkalemia
  • hypokalemia
  • fibrillation and heart block
  • hypercalcemia
  • hypocalcemia
40
Q

what are examples of drugs that alter the electrical activity?

A
  • Ca2+ channel blocker (decrease force of contraction)
  • Cardiac glycocides (increases force of contraction)
41
Q

what effect does Ca2+ channel blockers have on electrical activity?

A

decreases force of contraction

42
Q

what effect does cardiac glycocides have on electrical activity?

A

increases force of contraction

43
Q

what effect does temperature have on electrical activity?

A

increases about 10bpm per 1oC

44
Q

what effect does hyperkalemia have on electrical activity?

A

fibrillation and heart block

45
Q

what is hyperkalemia?

A

high plasma K+

46
Q

what is hypokalemia?

A

low plasma K+

47
Q

what effect does hypercalcemia have on electrical activity?

A

increased heart rate and force of contraction

48
Q

what effect does hypocalcemia have on electrical activity?

A

decreased heart rate and force of contraction

49
Q

what is hypercalcemia?

A

high plasma Ca2+

50
Q

what is hypocalcemia?

A

low plasma Ca2+

51
Q

what is fibrillation?

A

irregular heartbeat

52
Q

what is heart block?

A

blocking action potentials getting from the atrium to the ventricles

53
Q

what does the special conducting system ensure?

A

both atriums and ventricles contract at the same time

54
Q

what is A?

A

superior vena cava

55
Q

what is B?

A

sinoatrial node

56
Q

what is C?

A

right atrium

57
Q

what is D?

A

right bundle branch

58
Q

what is E?

A

right ventricle

59
Q

what is F?

A

purkinje fibres

60
Q

what is G?

A

inferior vena cava

61
Q

what is H?

A

left bundle branch

62
Q

what is I?

A

left ventricle

63
Q

what is J?

A

left atrium

64
Q

what is K?

A

bundle of His

65
Q

what is L?

A

atrioventricular node

66
Q

what is the process of the activation of the special conducting system?

A
  1. sinoatrial node (about 0.5m/s)
  2. atrioventricular node (about 0.05m/s, acts as a delay)
  3. bundle of His
  4. purkinje fibres (about 5ms, acts as a rapid conducting system)
67
Q

what do the left and right bundles of His break down into

A

purkinje fibres

68
Q

what do purkinje fibres ensure?

A

all of the ventricle contracts at the same time

69
Q

why is the delay of the atrioventricular node required?

A

so the atrium can get as much blood as possible into the ventricles

70
Q

what is the wave seen on an electrocardiogram?

A

summation of little action potentials in individual myocytes

71
Q

what is an electrocardiogram?

A

test used to check hearts rhythm and electrical activity

72
Q

what is A?

73
Q

what is BCD complex?

A

QRS complex

74
Q

what is E?

75
Q

what does the P wave correspond to?

A

atrial depolarisation

76
Q

what does the QRS complex correspond to?

A

ventricular depolarisation

77
Q

what does the T wave correspond to?

A

ventricular repolarisation

cardiovascular system (41 decks)

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