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Physiology > Electrophysiology > Flashcards

Electrophysiology Flashcards

1
Q

cardiac muscle features

A

intercalated disks
gap junctions
striated
involuntary

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2
Q

most superfical layer of the heart, it’s the visceral layer of the serous pericardium

A

epicardium

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3
Q

this is the middle layer of the heart, it’s composed of cardiac muscle and is the layer that contracts. It contains gap junctions.

A

myocardium

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4
Q

this is the inner layer of the heart which is continuous with the lining of the blood vessels

A

endocardium

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5
Q

true or false- every heart cell contracts with every beat of the heart

A

true

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6
Q

can the heart replace its muscle cells?

A

yes, but it is very limited
only about 1% per year

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7
Q

this is a small group of cells that depolarize spontaneously and the AP spreads through gap junctions in intercalated discs

A

conducting/ pacemaker cells

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8
Q

list the order of the pacemaker activation sequence

A

SA node
AV node
Bundle of His
Left and right branches
Purkinje fibers

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9
Q

SA node firing rate

A

70-80

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10
Q

AV node firing rate

A

40-60

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11
Q

Bundle of His firing rate

A

30-40

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12
Q

Purkinje fiber firing rate

A

15-20

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13
Q

are cardiac AP shorter or longer than skeletal or neuronal?

A

longer

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14
Q

nodal cells have _____ which means they spontaneously generate APs

A

Automaticity

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15
Q

explain 3 nodal depolarization events

A

1- slow Na+ through funny channels
2- T-type Ca2+ channels open
3- L-type Ca2+ channels open–> rapid depolarization

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16
Q

explain nodal repolarization

A

Ca2+ channels close
K+ channels open and K+ rushes out leading to repolarization

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17
Q

what is Bachmann’s bundle?

A

atrial projections for intratrial communication

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18
Q

what is the only path to the ventricles from the SA node?

A

internodal tracts to the AV node

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19
Q

which node has a pause?

A

AV node

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20
Q

Why does the AV node pause?

A

to allow the atria to empty

21
Q

what is the purpose of a long refractory period in the heart?

A

allows all activated muscle fibers to stay contracted for a set period of time

22
Q

this type of refractory period is more excitable than normal which makes it easier to fire another AP

A

supranormal refractory period

23
Q

explain the events that occur in heart muscle contraction phase 0- upstroke

A

Na+ rushing IN

24
Q

explain the events that occur in heart muscle contraction phase 1- initial repolarization

A

Na+ channels close and K+ channels open
K+ rushes out

25
Q

explain the events that occur in heart muscle contraction phase 2- plateau

A

L-type Ca2+ channels open
Ca2+ in= K+ out

26
Q

explain the events that occur in heart muscle contraction phase 3- repolarization

A

Ca2+ channels close
K+ channels remain open and K+ rushes out
hyperpolarization occurs
K+ channels close

27
Q

explain the events that occur in heart muscle contraction phase 4- resting membrane potentials

A

inward and outward currents are equal
Na+ and Ca2+ IN= K+ OUT

28
Q

what type of Ca+ channels do Ca2+ channel blockers inhibit?

A

L-type
leads to a lengthened refractory period

29
Q

how is Ca2+ removed from cardiac muscle?

A

NCX- Na/Ca2+ exchanger
SERCA- sarcoplasmic/endoplasmic Ca2+ ATPase

30
Q

is sympathetic or PS innervation a positive chronotrope

A

sympathetic

31
Q

is sympathetic or PS innervation a negative chronotrope?

A

PS

32
Q

is sympathetic or PS innervation a positive ionotrope?

A

sympathetic

33
Q

is sympathetic or PS a negative ionotrope?

A

PS

34
Q

this term refers to conduction velocity through the heart (how fast the signal moves through the heart)

A

dromotropic effects

35
Q

what does the sympathetic NS release on the heart and to what receptor type?

A

NE–> beta adrenergic on nodes, atria, and ventricles

36
Q

what does the PS NS release on the heart and to what receptor type?

A

ACh–> muscarinic receptors on nodes and atria

37
Q

how does ACh act as a negative chromotrope at SA and AV nodes?

A

decreases rate of depolarization by:
opens K+ channels–> K+ leaves
slows Ca2+ entry through T- channels

38
Q

how does ACh have negative ionotropic effects in atrial myocytes?

A

decreases available Ca2+ in plateau phase
increases K+ out- shortens plateau phase

39
Q

how does NE have positive chronotropic effects at the SA and AV nodes?

A

increases speed of depolarization
increases rate the Na+ and Ca2+ flow in
increases conductance of funny and T-type channels

40
Q

how does epinephrine have positive ionotropic effects at beta1 receptors on atrial and ventricular myocardial cells?

A

increases Ca2+ channel permeability
faster uptake of Ca2+ by Ca2+ ATPase–> faster relaxation and more Ca2+ for next contraction (phospholambin)

41
Q

how do beta blockers block ionotropic effects of the sympathetic NS?

A

blocks release of epinephrine from adrenal gland

42
Q

increased HR can also increase ______ by increasing overall Ca2+ influx

A

contractility

43
Q

what is an ECG?

A

composite of electrical activity
*not a single AP
*note node depolarization

44
Q

what is the p wave?

A

atrial depolarization

45
Q

what is the QRS complex?

A

ventricular depolarization

46
Q

what is the T wave?

A

ventricular repolarization

47
Q

when does atrial repolarization occur on an ECG?

A

QRS complex

48
Q

this is a group of positive ionotropic agents used to treat heart failure and includes digoxin

A

glycosides

49
Q

how does digoxin work?

A

inhibits Na/K ATPase
- less Na+ outside the cell means less to be used to pump Ca2+ out via NCX pumps and more Ca2+ stays in the cell
more intracellular Ca2+= stronger contraction

Physiology (18 decks)

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