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CVS > 03a: Electrophysiology > Flashcards

03a: Electrophysiology Flashcards

1
Q

Mechanical contraction of cardiac muscle is initiated by a(n) (X), a rapid (re/de/hyper)-polarization of the membrane.

A

X = action potential

Depolarization

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2
Q

Coordinated contraction of heart depends on initiation and spread of (X) over muscle in controlled, sequential manner.

A

X = action potential

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3
Q

T/F: Excitation of heart is neurogenic.

A

False - myogenic

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4
Q

List the three chief physiological properties of cardiac muscle function.

A
  1. Autorhythmicity/excitation
  2. Conduction
  3. Contraction
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5
Q

Pacemaker cells have (well/poorly)-developed contractile capability. Impulses originating there are conducted (quickly/slowly).

A

Poorly; slowly

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6
Q

Certain parts of the heart, such as (X) are specialized for rapid conduction of the impulse. They have (well/poorly)-developed contractile capability.

A

X = purkinje fibers;

Poorly

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7
Q

Which cardiac tissue has the highest degree of contractile power?

A

Atrial and ventricular muscle

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8
Q

List the heart regions in order of normal excitation.

A
  1. SA node
  2. AV node
  3. Common bundle of His
  4. Bundle branches
  5. Purkinje fibers
  6. Ventricular muscle
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9
Q

Non-pacemaker cells feature (small/large) negative value for resting membrane potential: (X) mV. This is due to high/low resting permeability to:

A

Large;
X = -90

High K+ and low Na+ permeabilities

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10
Q

T/F: Non-pacemaker cells of heart have qualitatively same action potential.

A

True

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11
Q

T/F: Non-pacemaker cells of heart have action potentials that are identical in total duration.

A

False

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12
Q

Course of electrical activity of heart is divided into how many phases?

A

5; phases 0-4

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13
Q

Phase 0 of heart AP.

A

Rapid depolarization (to peak)

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14
Q

Phase 1 of heart AP.

A

Initial repolarization (to plateau)

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15
Q

Phase 2 of heart AP.

A

Plateau

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16
Q

Phase 3 of heart AP.

A

Rapid repolarization (after plateau)

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17
Q

Phase 4 of heart AP.

A

Diastolic interval between successive AP

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18
Q

AP of heart lasts (shorter/longer) than nerve fiber AP. And (shorter/longer) than skeletal muscle AP.

A

Longer than both

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19
Q

Why is the duration of cardiac muscle AP almost as long as the contraction?

A

Acts more than trigger;

  1. Controls duration and magnitude of contraction
  2. Prevents cells fro becoming excitable before AP is over
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20
Q

(Short/long) refractory period in cardiac muscle serves to (allow/prevent) (X).

A

Long;
prevent;
X = muscle from being re-excited until previous contraction is essentially over

21
Q

T/F: In some cases, Purkinje cells can display spontaneous rhythmic activity.

A

True

22
Q

Chief distinguishing feature of pacemaker cell electrical activity is:

A

“Pacemaker potential”; slow depolarization in diastole (that leads to AP)

23
Q

T/F: Membrane of cardiac pacemaker cells is only at rest in diastole.

A

False - never at rest (slow depolarization in diastole)

24
Q

The “pacemaker potential” is:

A

slow depolarization occurring in pacemaker cells between discharges (during diastole)

25
Q

Pacemaker cells feature (small/large) negative value for resting membrane potential and AP whose overall time course is (faster/slower) than that of atrial muscle.

A

Small (closer to zero);

Slower

26
Q

What accounts for the (greater/lesser) negative resting potential in pacemaker cells?

A

Lesser (closer to zero);

Relatively high resting permeability to Na

27
Q

T/F: Rate of depolarization during pacemaker potential is identical in all pacemaker cells.

A

False

28
Q

Pacemaker cells having the (highest/lowest) (X) will control the rate of firing of other cell.s

A 
Highest;
Intrinsic frequency (reach threshold more rapidly)
29
Q

True pacemaker of the heart is (X). Reserve pacemaker is (Y).

A 
X = SA node
Y = AV node
30
Q

It can be seen that sympathetic effect of (increase/decrease) HR is due to (increase/decrease) in (X).

A

Increase;
Increase;
X = rate of rise in pacemaker depolarization

31
Q

Sympathetic innervation of heart (increases/decreases) maximum diastolic potential and (increases/decreases) rate of rise of (X).

A

No change;
Increases;
X = pacemaker potential

32
Q

Vagal innervation of heart (increases/decreases) maximum diastolic potential and (increases/decreases) rate of rise of (X).

A

Increases;
Decreases;
X = pacemaker potential

33
Q

Major (specific) effect of Ach, released by (X), is to (increase/decrease) (Y). This leads to (de/re/hyper)-polarization.

A

X = vagus
Increase;
Y = membrane permeability to K;
Hyperpolarization

34
Q

Which phase of cardiac cycle is the plateau phase, primarily due to (X) ion (influx/efflux)?

A

Phase 2;
X = Ca
Influx (counteracts K efflux)

35
Q

Plateau of cardiac cycle is typically around (X) mV.

A

X = 0

36
Q

Cardiac cycle: Compared to Na channels, Ca channels require (smaller/larger) (de/re/hyper)-polarization to trigger their opening. And they open (quicker/slower). And they are inactivated (quicker/slower).

A

Larger depolarization;
Slower;
slower

37
Q

During pacemaker potential, which ion(s) are responsible for (inward/outward) current that will result in depolarization of the membrane?

A

Inward;

First Na, then later Ca

38
Q

During diastole, conductance of (X) is turned off slowly, to allow slow (re/de/hyper)-polarization of the membrane.

A

X = K

Depolarization

39
Q

The “funny current” occurs during (X) period of cardiac cycle and is (inward/outward) current carried by (Y). What’s so funny about it?

A

X = diastolic
Inward;
Y = Na

It’s carried through Na channel that opens by repolarization (negative voltages)

40
Q

How (specifically) does NE cause (increase/decrease) rate of (X) depolarization?

A

Increase;
X = pacemaker

  1. Increase rate of turning off gK (during diastole)
  2. Increase gf (funny) and gCa
41
Q

On its way to (X), the electrical activity of heart pauses briefly to permit (Y).

A 
X = bundle of His (and ventricles);
Y = completion of atrial contraction
42
Q

T/F: Normally, conduction of AV node is bidirectional.

A

False - unidirectional (atrium to ventricles)

43
Q

The AV node will only transmit impulses up to a certain (X), after which various degrees of (Y) will occur.

A 
X = frequencies;
Y = heart block
44
Q

Sympathetic and vagal stimulation affect (X) speed through (Y) node.

A 
X = conduction
Y = AV
45
Q

Cardiac excitation: Once conduction reaches (X), the speed picks up and impulse spreads rapidly into (Y) network.

A 
X = bundle of His
Y = purkinje
46
Q

Role of Ca in initiating contraction: (influx/efflux) of (intra/extra)-cellular Ca triggers release of (X) from (Y).

A

Influx;
Extracellular;
X = Ca
Y = SR

47
Q

T/F: During plateau, uptake of Ca by SR is occurring.

A

True

48
Q

Sympathetic stimulation causes AP with (higher/lower) plateau amplitude due to (greater/smaller) (X).

A

Higher;
Greater;
X = gCa

49
Q

Sympathetic stimulation causes AP with (longer/shorter) duration in part from (faster/slower) (X).

A 
Shorter
Faster 
X = 
1. Inactivation of inward Ca current
2. Activation of repolarizing K current

CVS (11 decks)

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