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Cardio > Cardiac Electrophysiology > Flashcards

Cardiac Electrophysiology Flashcards

1
Q

Slowly and automatically depolarize to the threshold potential at which they fire an all or none action potential

A

Pacemaker cells

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2
Q

Cells involved in developing force during each contraction of the heart— they fire action potential when stimulated

A

Non-pacemaker

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3
Q

Pacemaker cells are specialized myocardial cells that are located in the

A

SA and AV nodes

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4
Q

Pacemakers cells are authorhythmic?

A

Yep, the spontaneously generate action potential

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5
Q

Pacemaker potential- phase 4

A

Depolarization- membrane potential slowly rises to threshold in SA and AV nodes

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6
Q

Step 2 is when

A

Action potential begins to fire once threshold is reached

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7
Q

Step 3 is when

A

There is a repolarization to resting potential

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8
Q

_____ response action potential

A

Slow

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9
Q

Funny current

A

Inward slow flux of Na+ through non-specific ion channels

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10
Q

Phase 4 depolarization involves 3 voltage gated membrane currents

A
  1. Decrease in outward flux of K+
  2. Funny current
  3. Gradual inlfux of Ca2+ as threshold is approached
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11
Q

Depolarization results from opening of voltage gated

A

L-type Ca2+ channels

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12
Q

Repolarization results from opening of voltage gated

A

K+ channels

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13
Q

The primary pacemaker in the intact heart with an intrinsic rhythm at rest of 60-100 depolarizations per minute

A

SA node

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14
Q

Depolarizers at a slower intrinsic rhythm and typically receives its signal from the SA node. It acts as a secondary pacemaker that can take over regulation of the heart if the SA node is damaged

A

AV node

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15
Q

Conducting network in the ventricles has an even slower intrinsic rhythm and could act as pacemakers only of the SA and AV nodes fail

A

His-purkinje fibers

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16
Q

All pacemakers share the same ionic mechanism of autorhythmicity

A

Yep

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17
Q

What happens when there is a parasympathetic action?

A
  1. Voltage gated K+ channels close more slowly- hyper polarizes resting potential
  2. Decreased funny current- reduces slope of phase 4 depolarizations
  3. Decrease in Ca2+ channels in late phase

This all leads to a slow heart rate

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18
Q

Parasympathetic innervation and mediator

A

Vagus n. And releases acetyl choline to SA node

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19
Q

Action of sympathetic intervention on heart

A
  1. Increased funny current in nodes and Ca2+ channels in all myocardial cells
  2. Alters threshold toward more negative voltage
  • this increases heart rate and increases force of contraction owing to increasing intracellular Ca2+ leading to a +/- inotropic effect
20
Q

Sympathetic innervation and mediator

A

Innervation is the cardiac plexus and releases Norepinephrine to SA and AV nodes and myocardium

21
Q

Non pacemaker cells true resting potential of

A

-90 mV

22
Q

Non pacemaker cells are excited by

A

APs from adjacent cells

23
Q

Phase 0

A

Rapid influx of Na+ through voltage gated channels leading to a depolarization towards ENa+

24
Q

Phase 1

A

Inactivation of Na+ channels plus opening of a transiently outward K+ channel

25
Q

Phase 2

A

Plateau phase involve an inward flux of Ca2+ through L-type. (Long lasting) voltage gated channels, balanced by a slow outward K+ current and Iks - voltage stays close to 0

26
Q

Phase 4

A

Small fluxes of Na+ and K+ maintain the resting potential

27
Q

Phase 3

A

Repolarization when Ca2+ channels close and potassium effluent, returns the membrane to resting potnetial

28
Q

Non pacemakers cells have a rapid depolarization thus they are referred to as

A

Fast response

29
Q

Period comprising phases0,1,2, and part of 3, during which a new action potential cannot be elicited

A

Effective or absolute refractory period

30
Q

Are Na+ channels inactivated during refractory period?

A

Yep

31
Q

Duration of ERP (effective refractory period) can be 100-250 msec; _____ times for atrial muscle and _____ for ventricular

A

Shorter times for atrial muscle and longer for ventricular

32
Q

Significance of ERP

A

Limits the frequency AP and prevents the heart from summing twitches or tetanizing thus allowing time for ventricular filling between beats

33
Q

In atrial and ventricular myocardium conduction of AP is primarily by cell-cell contact through

A

Gap junctions

34
Q

Gap junctions contain ______ resistance ion channels that allow depolarizing currents to spread from one cell to adjacent cells

A

Low

35
Q

Explain to me the sequence of the activation of the heart

A
  1. SA node fires AP
  2. Signal is conducted through the atrial muscle cell to cell
  3. Signal reaches the AV node which is the only conducting pathway from the atria into the ventricles
  4. Small diameter fibers within the AV node delay conduction of the impulse into the ventricular muscles
    5/ fibers leaving the AV node expand and enter the ventricles at the base of the septum= bundle of His
  5. Bundle of His divides into right and left brindle branches that ratify down the Endo cardinal surfaces of the septum spreading laterally
  6. Bundle branch fibers divide into purkinhe fibers that spread the impulse into the ventricular myocardium to individual myocytes which then conduct via gap junction
36
Q

Junctions fibers are slow or fast acting fibers?

A

Slow that is why we see a delay in conduction into the ventricular muscle

37
Q

Spread of impulse

A

Septum—> apex—> base and endo—> epicardium

38
Q

Duration of APs is longer in _____ and ________ myocytes than in _______ myocytes

A

In bundle branches and subendocardial are longer than in subepicardial

39
Q

Who are the last to depolarize but are the first to repolarize

A

Subepicardial myocytes

40
Q

Ventricular depolarizations spreads _______ over the pathway of depolarization

A

Backwards

41
Q

Dipoles measure and record electrical changes on the

A

Outside fo the muscle strip

42
Q

Dipoles exist when there is a

A

Separation of charge along the muscle strip

43
Q

If the tissue is uniformly charge— isoelectric— how are the dipoles?

A

No dipoles exist

44
Q

When a dipole vector indicating depolarization it points toward the positive electrode the signal is

A

positive

45
Q

When a dipole vector indicating repolarization points toward the positive electrode, the signal is

A

Negative

46
Q

Electrodes placed perpendicularly to a dipole vector it shows

A

No deflection

Cardio (26 decks)

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