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[OS 205] Thorax > Electrophysiology of the Heart > Flashcards

Electrophysiology of the Heart Flashcards

1
Q

3 Muscles of the Heart

A
  1. Atrial Muscles2. Ventricular Muscles3. Conductive Muscle Fibers
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2
Q

Intercalated Discs

A

Connection of heart muscle cells

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3
Q

Desmosomes

A

Structural element that combines them

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4
Q

Gap Junctions

A

Ion channels that allow ions to move freely between cells, allowing electrical impulse

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5
Q

Contractile Cells

A
  1. Compose most of the heart2. Contract when stimulated
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6
Q

Auto-rhythmic Cells

A
  1. Comprise the conducting system2. Self-stimulating and can contract/depolarize without external stimulus
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7
Q

Fast Response Cells

A
  1. Atrial and Ventricular Myocytes2. Purkinje Fibers
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8
Q

Examples of Slow Response Cells

A
  1. SA Node2. AV Node
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9
Q

Resting Membrane Potential

A

-80-90mV Interior Negative

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10
Q

Phase 0

A
  • Higher K insid ethe cell- Sudden opening of fast and slow Na+ channels- Rise in Na+ permeability- Drop in K+ permeability
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11
Q

Tetrodotoxin

A

Blocks Na+ Channels

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12
Q

Phase 1 (Also called?)Blocked by?

A

Repolarization- K+ channels open- Primarily caused by closing of Na+ ion channels and opening of K+ ion channelsBlocked by 4-aminopyridine

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13
Q

Phase 2 Activators and Blockers

A

A: Catecholamines: Increase ECF-Ca2+ ConcentrationB: Ca2+ Antagonists and Mn2+

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14
Q

Phase 2 (Or?)1. What changes to voltage?2. What channels are open?3. What’s happening?

A

Plateau Phase1. Voltage is constant2. Ca2+ channels are open (Some K+ leaking out, causing balance)3. Prolongs duration of contraction, prevent overstimulation

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15
Q

Phase 3 (Or?)What channels are open?

A

Genesis/Final RepolarizationOnly K

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16
Q

Phase 4 (Or?)1. What is working in this stage?2. What happens to Ca2+?

A

Rest Phase

  1. Na-K ATPase pump works to remove Na+ and returns K+
  2. Ca2+ exchanged for Na+
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17
Q

Major Differences of Skeletal and Cardiac Muscles?

A
  1. Presence of both fast Na+ and slow Ca2+ channels in Cardiac Muscles2. Decreased K+ channel permeability after action potential: Prevents premature return to resting levels
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18
Q

Absolute Refractory Period

A

Cannot be stimulated no matter what

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19
Q

Effective Refractory Period

A

Can only be stimulated by a larger than normal stimulus

Only a local response can be produced

No action potential generated

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20
Q

Relative Refractory Period

A

Action Potential can only be stimulated by a larger than normal stimulus

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21
Q

Supernormal Period

A

More excitable than normal; ala a weaker stimulus can cause depolarization

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22
Q

Full Recovery Time in Fast Response and Slow Response cell is dependent on?

A

Fast-Response: Voltage-DependentSlow-Response: Time-Dependent

23
Q

Effects of VMAX

A

More VMAX :: More Conduction

24
Q

Diameter

A

Fatter Cell : Faster

25
Q

Changing Resting Membrane Potential

A

More Negative :: More Quicker

26
Q

Conducting System Pathway

A

SA Node -> Atrium -> AV Node -> Bundles of His -> Purkinje Fibers -> Ventricular Muscles

27
Q

SA Node Resting Potential

A

-55 to -60mV

28
Q

Why is the SA Node Membrane Naturally Leaky to Sodium Ions?

A
  • Enter through slow sodium channels- More permeable to Na due to higher extracellular concentration- Faster heart rate : More Sodium
29
Q

Fast, Slow, or both Na+ channels for SA Nodes?

A

Only slow, fast channels are blocked due to less negativity

30
Q

Threshold Voltage of SA Node

A

-40 mV

31
Q

Bachmann’s Bundle

A

Conducts impulse from SA node -> Left Atrium

32
Q

AV Node Function

A

Delays the impulse from the atria to the ventricle to allow for more contraction time

33
Q

Purkinje System Transmission Rate

A

1.5-4m/s (Fastest)

34
Q

Hierarchy of Pacemakers

A
  1. SA Node: 70-80 bpm2. AV Node: 40-60 bpm3. Purkinje Fibers: 15-40 bpm
35
Q

Which pacemaker is most dominant and why?

A

The SA Node, because it has the fastest rate of depolarization preventing others from self-exciting

36
Q

Stokes-Adam Syncope

A

Occurs when SA node fails and takes time for the AV node to take over; causes you to faint

37
Q

Parasympathetic Nerves:1. Innervates2. Secretes

A
  1. Mainly sinus and AV node, some parts of the two atria and little to the ventricular muscles2. Acetylcholine
38
Q

Acetylcholine Effects

A
  1. Decreases rate of rhythm of sinus node2. Decreases excitability of the AV junctional fibers between atrial musculature and AV node3. Slows down heart rate
39
Q

Mechanism of Parasympathetic Nerves

A

Increases permeability of K+ ions out of cell, causing hyperpolarization

40
Q

Sympathetic Nerves1. Innervates2. Secretion

A
  1. All parts of the heart2. Norepinephrine
41
Q

Norepinephrine Effects

A
  1. Increases rate of sinus node discharge2. Increases rate of conduction and excitability3. Increases force of contraction
42
Q

P Wave

A

Atrial Depolarization

43
Q

QRS Complex

A

Ventricular Depolarization

44
Q

T Wave

A

Ventricular Repolarization

45
Q

ECG X and Y Axis

A

X: TimeY: Voltage

46
Q

ECG Small Box, Big Box

A

Small Box: 0.04sBig Box: 0.2s (equal to 5 small boxes)

47
Q

Normal QRS Axis

A

Between -30 and +90 degrees

48
Q

Increased Voltage in ECG

A
  • Normal 0.5 to 2.0mV- Commonly caused by ventricular hypertrophy
49
Q

Decreased Voltage in ECG

A
  • Decreased Muscle Mass- Pericardial Effusion: Fluid shorts the currents- Pulmonary Emphysema: Excessive air in lungs act as insulators
50
Q

Prolonged QRS Complex

A
  • Cardiac Hypertrophy or Dilation: Increased distance for current to travel to depolarize- Purkinje System Blocks
51
Q

T Wave Abnormality

A

Caused by conduction blocks, premature contractions or prolonged depolarizatoin

52
Q

Tachycardia

A

> 100 BPM- Increased temperature- Sympathetic Stimulation

53
Q

Bradycardia

A

< 60 BPM

[OS 205] Thorax (10 decks)

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