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2023 Systems Phys > Cardiac Electrophysiology > Flashcards

Cardiac Electrophysiology Flashcards

1
Q

When is the cardiac membrane most permeable to potassium?

A

At rest

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2
Q

What happens in a cardiac cell when the Sodium Potassium Pump is inhibited?

A

RMP becomes less negative
Cell hyperpolarizes
Cell becomes more excitable

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3
Q

What are the four phases of a normal cardiac action potential?

A

Phase 4 - RMP
Phase 0 - Rapid Upstroke
Phase 1 - Partial Repolarization
Phase 2 - Plateau
Phase 3 - Repolarization
Phase 4 - RMP

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4
Q

What happens to fast sodium channels during phase 1 of the cardiac musclr action potential?

A

They inactivate

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5
Q

When is the cardiac muscle membrane most permeable to Sodium?

A

Phase 0

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6
Q

When is the cardiac muscle membrane most permeable to Calcium?

A

Phase 0

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7
Q

What is the pathway of a Fast Na+ Channel?

A

Voltage of the membrane increases
Activation gate is activated and opens Fast Na+ channel
Na+ Enters channel
High membrane voltage triggers inactivation gate
Channel closes

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8
Q

What happens to the action potential of a cardiac muscle given tetrodotoxin?

A

Phase 0 is eventually lost and the Fast Na+ channel is blocked

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9
Q

How does Diltiazem affect cardiac muscle?

A

It blocks L=Type Ca2+ channels and shortens phase 2
Lacl of Ca2+ causes contraction to weaken

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10
Q

What is important for contraction during phase 2?

A

influx of Ca2+ ions

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11
Q

What is the purpose of the ARP?

A

Long ARP protects the cardiac muscle from tetanus because it prevents another AP from firing

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12
Q

In cardiac muscle, what occurs first, Mechanical activity or Electrical activity?

A

Electrical activity proceeds mechanical activity

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13
Q

Which parts of the cardiovascular system experience fast response?

A

Atrium
Ventricle
Purkinje FIbers

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14
Q

Which parts of the cardiovascular system experience slow response?

A

SA Node
AV Node

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15
Q

Why is the atrium AP different fron the ventricle and purkinje AP?

A

Atrium generates less force and ha a shorter phase 2

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16
Q

Which node is the typical pacemaker?

A

SA Node

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17
Q

What happens if the SA Node cannot function properly as the pacemaker?

A

The AV Node will take over

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18
Q

Where is the SA Node located?

A

Between the Super Vena Cave and Atrium

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19
Q

Where is the AV Node located?

A

Between the Atrium and Ventricle

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20
Q

What is the difference between fast response and slow response tissues?

A

Fast Response Tissues have Fast Na+ Channels
Slow responsse do not

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21
Q

Why is the SA Node the dominate pacemaker?

A

The SA Node has the highest rate of depolarization

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22
Q

What causes Phase 0 in SA Nodal cells?

A

Increase in Ca2+ permeability

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23
Q

What do If channels do in SA Nodal Cells?

A

Conduct Na+ at rest
Na+ leaks in
Ca2+ leaks out

24
Q

What causes the action potential in SA Nodal Cells?

A

SA Nodal Cells spontaneously move toward threshold and fire AP

25
Q

How does Sympathetic Stimulation from the SNS affect Cardiac Muscle?

A

SNS releases NE
NE binds B1 receptors
K+ permeability decreases
Na+/Ca2+ permeability increase
Heart Rate increases

26
Q

How does Parasympathetic Stimulation from the PSNS affect Cardiac Muscle?

A

PSNS releases ACh
ACh binds M1 receptors
K+ permeability increases
Na+/Ca2+ permeability decrease
Heart Rate decreases

27
Q

Which branch of the ANS causes cardiac muscle to reach threshold more quickly?

A

SNS

28
Q

Which ANS system dominates at rest?

A

PSNS

29
Q

What happens if you cut all ANS innervation from the heart?

A

Heart Rate increases

30
Q

What happens to heart rate when the PSNS is stimuated?

A

Heart Rate Decreases

31
Q

What happens to Heart Rate when the SNS is stimulated?

A

Heart Rate Increases

32
Q

What happens when sympathetic innervation to the heart is cut?

A

Heart rate decreases

33
Q

Whatr happens when parasympathetic innervation to the heart is cut?

A

Heart Rate Increases

34
Q

What is the normal sequence of activation for cardiac muscle electrical activity?

A

SA Node -> Atrial Myocardium -> AV Node -> AV Bundle -> Bundle Branches -> Purkinje Network -> Ventricular Myocardium

35
Q

Which node has the slowest conduction velocity?

A

AV Node

36
Q

What are the requirements for reentry?

A

Unidirectional Block
The absolute refractory period of the reentered tissue must be shorter tan the propagation time around the reentry loop

37
Q

Why is Ca2+ important in the heart?

A

The heart is highly dependent on extracellular Ca2+ for contractile function

38
Q

Why would tetanus be bad in the heart?

A

No blood could be pumped during tetanus

39
Q

Which refractory period prevents any stimulus, no matter how strong, from generating an action potential?

A

ARP

40
Q

How does the RRP affect the action potential?

A

It would have a lower amplitude than normal and a reduced rate of rise due to the fast Na+ channels not being completely reset and the gradients fully reestablished

41
Q

What in is responsible for the pacemaker activity in SA Nodal cells?

A

The unstable resting membrane potential of the cells

42
Q

What causes the prepotential in SA Nodal Cells?

A

The cells are more permeable to Na+ at rest (RMP) and they exhbit a gradual decline in the K+ conductance through their cell memrbanes

43
Q

What factors produce the SA Nodal prepotential?

A

Increased Na+ conductance at rest
Gradually decreasing K+ conductanc
Slow Ca2+ influx

44
Q

How do you slow the pacemaker discharge?

A

Decrease rate of depolarization
Hyperpolarize the cell
Change threshold potential

45
Q

What are the components of the conduction system?

A

SA Node
Atrial internodal pathways
AV Node
Bundle of His or AV Bundle
Bundle Branches
Purkinje System
Ventricualr Muscle

46
Q

How does the SA Node spread impulses?

A

Impulses move out of the SA node through the internodal pathways to the AV Node

47
Q

Where does the main delay of SA Node impulses occur?

A

In the AN Zone of the AV Node

48
Q

How does the sympathetic nervous system affect the AV node?

A

Increases conduction velocity

49
Q

How does the parasympathetic system affect the AV Node?

A

Decreases conduction velocityin AV Node

50
Q

Why is the AV Node a critical region for heart block development?

A

Under normal conditions, it is the only region where impulses from the atria can get to the ventricles

51
Q

Sumarizes the process of Excitation-contraction coupling and uncoupling…

A
  1. Voltage-depedent calcium influx
  2. Calcium release from SR
  3. Removal of calcium from cytosol
  4. b-receptor activation (catecholamines)
  5. Action of cardiac glycosides (digitalis)
  6. Excitation-contraction uncoupling
52
Q

What are the mechanisms of calcium release in cardiac cells?

A

Ca induced Ca release
Charge movement coupled Ca release
IP3 induced Ca release

53
Q

Which of the following statements regarding the autonomic nervous system is correct:
A. Parasympathetic activity increases the membrane permeability to K+
B. Sympathetic innervation decreases the slope of the pacemaker potential
C. Sympathetic innervation decreases the membrane permeability to Na+ and Ca2+
D. The heart will stop beating if it is denervated
E. The heart rate will decrease significantly if the heart is denervated

A

A. Parasympathetic activity increases the membrane permeability to K+

54
Q

Which of the following is MOST responsible for phase 0 of the SA Nodal Phase:
A. Pacemaker Channels
B. Voltage-gated Ca2+ channels
C. Tetrodotoxin-sensitive Na+ channels
D. K+ leak Channels
Cl- Channels

A

B. Voltage-gated Ca2+ channels

55
Q

Which one of the following would increase the rate of phase 4 depolarization in an SA nodal cell?
A. An increase in SA Nodal K+ conductance
B. Stimulation of cardiac muscarinic receptors
C. Stimulation of the vagus nerve
D. Increasing levels of circulating epinephrine

A

D. Increasing levels of circulating epinephrine

56
Q

In the normal heart, premature re-excitation of myocytes is prevented by:
A. Gating properties of the gap junctions within the intercalated disks
B. Offsetting multiple reentry mechanisms
C. The ARP of the myocardial cells
D. Rapid re-setting (h-gates open; m-gates close) of the voltage-gated, fast sodium channels
E. Overdrive Suppression of secondary pacemakers

A

C. The ARP of the myocardial cells

57
Q

During Atrial Fibrillation, the rate of ventricular depolarization depends on …
A. The firing ate of the SA node
B. The refractory period of cells in the AV node
C. The conduction velocity in the atrial internosal tracts
D. The conduction velocity of the Purkinje Gibers
E. None of the above

A

B. The refractory period of cells in the AV node

2023 Systems Phys (41 decks)

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