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CVS > CVS Physiology 2: Cardiac Electrophysiology And Excitation-contraction Coupling. > Flashcards

CVS Physiology 2: Cardiac Electrophysiology And Excitation-contraction Coupling. Flashcards

1
Q

List the 4 basic properties essential for the heart to function as the central pump?

A

1- autorhythmicity.
2- conductivity.
3- excitability.
4- contractility.

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2
Q

Definition: generating its own electrical impulse rhythmically.

A

Autorhythmicity.

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3
Q

Definition: ability to conduct electric impulse.

A

Conductivity.

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4
Q

Definition: ability to respond to stimuli by producing electrical action potentials.

A

Excitability.

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5
Q

Definition: a capacity for shortening in response to suitable stimulus.

A

Contractility.

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6
Q

Electrical impulses are generated and conducted in the _______.

A

Heart.

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7
Q

Excitation wave starts from _________ _______ (__ m/s), then to __________ ______ (__m/s), the to the ________ _______ (__ m/s), finally to ______ ____ ____ and ____ ____ _____ (__m/s).

A

Excitation wave starts from sinoatrial node (SAN) = (1m/s).
Then to atrioventricular node (AVN) = (0.05m/s).
Then to the atrioventricular bundle (AVB) = (1m/s).
Finally to:
Right bundle branch (RBB).
Left bundle branch (LBB).
(4m/s).

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8
Q

Which node is the dominant node?

A

SA node “pacemaker”.

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9
Q

Why does the AV node have a 100-msec delay?

A

Allows time for ventricular filling.

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10
Q

List the order of pacemaker rates?

A

SA > AV > bundle of His/purkinje/ ventricles.

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11
Q

List the order of the speed of conduction?

A

Purkinje > atria > ventricle > AV node.

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12
Q

List the 3 ions in the resting ventricular muscle cell?

A

1- K+.
2- Na+.
3- Ca2+.

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13
Q

What is the intracellular concentration of K+ in the resting ventricular muscle cell?

A

135 mEq/L.

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14
Q

What is the intracellular concentration of Na+ in the resting ventricular muscle cell?

A

10 mEq/L.

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15
Q

What is the intracellular concentration of Ca2+ in the resting ventricular muscle cell?

A

.0001 mEq/L.

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16
Q

What is the extracellular concentration of K+ in the resting ventricular muscle cell?

A

4
(Meaning it moves from intracellularly to extracellularly).

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17
Q

What is the extracellular concentration of Na+ in the resting ventricular muscle cell?

A

145
(Meaning it moves from extracellularly to intracellularly).

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18
Q

What is the extracellular concentration of Na+ in the resting ventricular muscle cell?

A

2
(Meaning it moves from extracellularly to intracellularly).

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19
Q

What is the equilibrium potential of K+ in the resting ventricular muscle cell?

A

-94 mV.

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20
Q

What is the equilibrium potential of Na+ in the resting ventricular muscle cell?

A

+70 mV.

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21
Q

What is the equilibrium potential of Ca2+ in the resting ventricular muscle cell?

A

+132 mV.

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22
Q

What is the permeability of K+ in the resting ventricular muscle cell?

A

High.

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23
Q

What is the permeability of Na+ in the resting ventricular muscle cell?

A

Low.

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24
Q

What is the permeability of Ca2+ in the resting ventricular muscle cell?

A

Low.

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25
Q

List the 3 main groups of membrane channels?

A

1- ungated channels.
2- voltage - gated channels.
3- ligand - gated channels.

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26
Q

Which membrane channel is concentration based?
And give an example?

A

Ungated channels.
E.g: K+ channel.

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27
Q

Which membrane channel is voltage dependent?
And give an example?

A

Voltage - gated channel.
E.g: Na+ channels, Ca2++ channels, K+ channel.

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28
Q

Which membrane channel is ligand (protein) dependent?
And give an example?

A

Ligand - gated channel.
E.g: acetylcholine gated.

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29
Q

What is the way of diffusion of ungated channels?

A

Passive diffusion.

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30
Q

List the 2 types of cardiac muscle fibers?

A

1- contractile fibers.
2- excitatory and conductive fibers (auto rhythmic cells).

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31
Q

What is the major cardiac muscle fiber?

A

Contractile fibers.

32
Q

Which cardiac muscle fiber is responsible for the generation and conduction of the excitation wave of all parts of the cardiac muscle?

A

Excitatory and conductive fibers (auto rhythmic cells).

33
Q

Which cardiac muscle fibers constitute the atrial and ventricular walls?

A

Contractile fibers.

34
Q

Which cardiac muscle fibers is responsible for the pumping action of the heart?

A

Contractile fibers.

35
Q

What do the excitatory and conductive fibers (auto rhythmic cells) include? (5)

A

1- SAN fibers.
2- AVN fibers.
3- bundle of His = A-V bundle.
4- Rt and Lt bundle branches.
5- purkinje fibers.

36
Q

Definition: the intracellular potential of the resting cell?

A

Resting membrane potential (RMP).

37
Q

What is the resting membrane potential (RMP) of a resting myocyte?

A

-90 mV.

38
Q

In atria and ventricular cells, the resting membrane potential is _____, until ______ _____ is applied.

A

Stable until external excitation is applied.

39
Q

In the SA node cells, membrane potential is ___ _____ and called as the ______ _______, always moving towards the ____ ____ with time.

A

Not stable and called as the pacemaker potential, always moving towards zero millivolts (mV) with time.

40
Q

Definition: negative intracellular potential moves towards zero and then becomes positive.

A

Depolarization.

41
Q

Give an example of depolarization?

A

Na+ or Ca2+ influx depolarizes cell.

42
Q

Definition: negative intracellular potential is re-established after depolarization.

A

Repolarization.

43
Q

Give an example of repolarization?

A

K+ efflux repolarizes cells.

44
Q

What effect would increasing the extracellular K+ ion has? What is the net result?

A

Reduce the efflux of K+ ions or even create an influx of K+ ions, the net result will be depolarization.

45
Q

What effect would decreasing the extracellular K+ ion has? What is the net result?

A

Accelerate the efflux of K+ ions, the net result of which will be hyperpolarization.

46
Q

A cell’s resting membrane potential is very sensitive to change in what?

A

A change in extracellular K+ ions.

47
Q

What is the response of cardiac action potential in ordinary myocytes?

A

Fast response.

48
Q

What is the response of cardiac action potential in nodal muscle fibers?

A

Slow response.

49
Q

Where does the fast response of cardiac action potential occur?

A

Occurs in atrial, ventricular muscles and purkinje fibers.

50
Q

Where does the slow response of cardiac action potential occur?

A

Occurs in the SA and AV.

51
Q

What is membrane potential of SAN?

A

SA has unstable membrane potential,
(-55:-60).

52
Q

Which channels open and close with Low K and high Na? (Extracellularly)

A

Closure of K+ channels.
Opening of “funny” channels (Na+ channels).

53
Q

Which channels open and close with high Ca?

A

Opening of voltage-gated Ca++ channels (transient, T-type channels).
Closure of funny channels.

54
Q

Which channels open and close with high high Ca?

A

Opening of voltage-gated Ca++ channels (long, L-type channels).
Closure of T-type Ca++ channels.

55
Q

Which channels open and close with high K and low Ca?

A

Opening of voltage-gated K+ channels.
Closure of voltage-dependent Ca++ channels (L-type).

56
Q

List the 2 effects of parasympathetic stimulation?

A

1- hyperpolarize&raquo_space; increasing conductance out of cell and decrease “funny current” (sodium) and calcium conductance.
2- decrease in the slope if pre potential&raquo_space; takes longer to reach the threshold&raquo_space; intrinsic firing decreases.

57
Q

List the 2 effects of sympathetic stimulation?

A

1- activation of beta receptors&raquo_space; increased “funny current” (sodium) and increased calcium influx.
2- increase in the slope of prepotential&raquo_space; threshold is reached sooner&raquo_space; intrinsic firing increases.

58
Q

Increased Ca2+ premeability in cardiac myocytes has which effects?

A

Increased contractility and increased SV.

59
Q

What happens in phase 0 of electrical activity?

A

Depolarization of the membrane to -65 mv leads to opening of fast Na+ channels, this causes rapid influx of Na+ ions.

60
Q

What happens in phase 1 of electrical activity?

A

Brief repolarization caused by K+ efflux.

61
Q

What happens in phase 2 (plateau) of electrical activity?

A

Balance between inward Ca++ and outward K+.

62
Q

What is the importance of the plateau phase?

A

Important to maintain contraction for adequate time to empty the heart chambers.

63
Q

What happens in phase 3 of electrical activity?

A

Rapid repolarization,
Causes:
1- inactivation of Ca++.
2- activation of outward K+ channels (delayed rectifier).

64
Q

What happens in phase 4 of electrical activity?

A

Causes: continuous activation of outward K+ channels.

65
Q

How long does the absolute refractory period lasts?

A

Lasts almost the entire time of one cardiac muscle twitch (one contraction).

66
Q

What happens by the time the action potential and muscle contractions are fully over?

A

No tetany of cardiac muscle possible.

67
Q

What happens when Ca++ ions enter the cardiac muscles?

A

Induces Ca++ release from sarcoplasmic reticulum.

68
Q

The heart is a syncytium of many cells electrically connected at intercalated discs by _______ _______?

A

Gap junctions.

69
Q

Cardiac muscle is _______ type and contain __ _____ and highly developed _______ ___ _______.

A

Striated type and contain T-tubules and highly developed intracellular SR networks.

70
Q

_____ _____ provide the excitation stimulus used to activate plasma membrane Ca2+ channels causing a substantial ____ ______.

A

Action potentials.
Ca2+.

71
Q

Ca2+ induces Ca2+ release (CICR) through which channel?

A

Ryanodine receptor channels (RyR).

72
Q

What does local release of Ca2+ cause?

A

Causes calcium sparks.

73
Q

Calcium ion binds to what to initiate contraction?

A

Troponin.

74
Q

What occurs when calcium unbinds from troponin?

A

Relaxation.

75
Q

Ca2+ is pumped back into SR for what?

A

Storage.

76
Q

Ca2+ is exchanged with what?

A

Na+.

77
Q

Na+ gradient is maintained by what?

A

Na-K-ATPase pump.

CVS (11 decks)

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