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Physiology > Cardiac Electrophysiology > Flashcards

Cardiac Electrophysiology Flashcards

1
Q

what is the muscle cell of the heart?

A

the cardiac myocyte

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2
Q

how is the cardiac muscle similar to skeletal muscle?

A

it is striated and multinucleated

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3
Q

how is the cardiac muscle similar to smooth muscle?

A

the nuclei are centrally located and many cells are needed to span the length of the muscle

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4
Q

how is cardiac muscle different from both smooth and skeletal muscle?

A

the cells branch out and are joined by intercalated disks

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5
Q

what cells allow the heart muscle to contract without nervous input?

A

pacemaker cells

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6
Q

describe the intercalated discs in cardiac muscle

A

they are irregular transverse thickening of the sarcolemma between attached muscle cells

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7
Q

what are the two major sub-components of an intercalated disc?

A

desmosomes and gap junctions

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8
Q

function of desmosome is to…

A

hold adjacent cells together, they act as “spot welds”

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9
Q

the function of gap junctions are to…

A

allow ions to pass between cells (via their charge), also helps the cardiac muscle to act as one via a functional syncytium

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10
Q

the thick filaments are largely composed of what?

A

myosin

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11
Q

the thick filaments span the length of the __ band

A

A-band

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12
Q

the thing filaments are made most of what?

A

actin, tropomyosin, and troponin

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13
Q

the thin filaments span the length of what?

A

the I band

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14
Q

how many phases are there to a ventricular action potential?

A

5

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15
Q

which phase is the “upstroke”?

A

phase 0

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16
Q

which phase is the “early repolarization”?

A

phase 1

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17
Q

which phase is the “plateau/ERP(effective refractory period)”?

A

phase 2

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18
Q

what phase if the “repolarization”?

A

phase 3

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19
Q

in what phase is the action potential returned to the resting membrane potential?

A

phase 4

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20
Q

the resting membrane potential is largely determined by what ion and why?

A

K+, because this is when an equilibrium between the force driving potassium out the the cell is equal to the electrical force driving it into the cell

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21
Q

the upstroke in phase 0 is caused by the opening of what gates?

A

voltage gated sodium gates, sodium comes into the cell in phase 0

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22
Q

in phase zero is the opening of sodium gates complete or partial?

A

it depends on the stimulus, rapid stimulus causing complete opening and partial stimulus causes only partial opening

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23
Q

what causes the early repolarization in phase 1

A

the brief outward movement of potassium ions and the simultaneous inward movement of Cl-

24
Q

what is the most important aspect of phase 2, the plateau?

A

it creates a prolonged refractory period in which the muscle cannot be re-excited

25
Q

the plateau in phase 2 is maintained mainly by the slow inward movement of ___ ions

A

Ca+

26
Q

the repolarization in phase 3 is caused by the net outward movement of __ ions

A

K+

27
Q

phase 4, the returned resting potential is characterized by the slow leak of __ into the cell

A

Na+

28
Q

the voltage gated sodium channels responsible for phase 0 are very similar to voltage-gated channels where else in the body?

A

in the neurons

29
Q

what are the two types of voltage gated sodium channels?

A

m-activation (phase 0) and inactivation (phase 3)

30
Q

which potassium channel is responsible for phase 1, but remains active until after phase 2?

A

i(to)

31
Q

which potassium channel is slow acting in phase 2 and responsible for phase 3?

A

i(kr)

32
Q

which potassium channel is responsible for maintaining flux in phases 3 and 4?

A

i(k1)

33
Q

which potassium channel is activated by acetylcholine and Gi-coupled?

A

i(k ACh1)

34
Q

which calcium channels are the most predominant in the heart?

A

the L-type (long lasting) = i(ca)

35
Q

describe the L-type calcium channels = i(ca)

A

they are long lasting, but slow activation

36
Q

what is the less abundant type of calcium channels in the heart?

A

T-type (transient)

37
Q

which type of calcium channels do calcium channel blockers target?

A

L-type = i(ca)

38
Q

what two things are flowing in phase 2 and in what direction?

A

calcium in, potassium out

39
Q

why are the T tubules in cardiac muscle larger than that in skeletal muscle?

A

because cardiac muscle is sensitive to extracellular Ca and skeletal is not, the T tubules help them to be more sensitive to the external conc of Ca

40
Q

the purpose of cardiac glycosidases, such as _____, is to ____ cardiac contractility

A

digitalis/digoxin, increase (cardiac contractility)

41
Q

how to cardiac glycosidases work?

A

they inhibit membrane sodium pumps (that move Na out of the cell) an increase in intracellular Na, means inhibition of the Na-Ca exchange, thus more intracellular Ca = more cross-bridging = stronger contration

42
Q

excess K+ causes the heart to become ____

A

weak

43
Q

what does excess K+ do to the heart?

A

the lack of a K+ gradient induces depolarization the causes a weak cardiac action potential (b/c cardiac AP and contraction are related)

44
Q

the magnitude of cardiac AP is related to….

A

the strength of the contraction

45
Q

the spontaneous depolarization of the SA node is due to the leakage of what ion?

A

Na+

46
Q

If the SA node has an intrinsic firing rate of 100x per minutes then why isn’t that our resting HR

A

because the PNS is constantly putting a break on the SA and AV node

47
Q

the PNS innervates the AV and SA node with what nerve?

A

the vagus nerve

48
Q

the PNS innervation causes the release of ___ which opens __ channels

A

AcH, K+ channels

49
Q

opening K+ channels causes what to happen?

A

hyperpolarization, thus increasing the time for the AP to reach threshold

50
Q

why is it important that both the SA and Av nodes are in the atria?

A

it allows time for the atria to top of the ventricles before it contracts

51
Q

the SNS innervates what?

A

the SA node and the ventricles

52
Q

SNS innervation causes the release of ___ which opens __ channels

A

NE, Ca+

53
Q

the opening of Ca+ channels causes what to happen?

A

depolarization, thus decreasing the time for the AP to reach threshold

54
Q

the SNS release of Ca+ in the ventricles increase what two things?

A

increase CO because of more contractions but also increase in the strength of the contraction itself

55
Q

chronotropism

A

heart rate

56
Q

+ chronotropism

A

tachycardia

57
Q
  • chronotropism
A

bradycardia

Physiology (4 decks)

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