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Physiology > Cardio Electrophysiology 2 > Flashcards

Cardio Electrophysiology 2 Flashcards

1
Q

Where is the SA node located?

A

The Endocardial surface of the RA, in the junction of the Superior Vena Cava and RA appendage.

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2
Q

What are the dimensions of the SA node?

A

15 mm x 5 mm x 2 mm thick

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3
Q

What are the terms for UNSTABLE resting membrane potential?

A

Prepotential
Pacemaker potential
Diastolic depolarization

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4
Q

What is the resting membrane potential of a SA node?

A

-70 mV

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5
Q

What is the maximum membrane potential of a Ventricular Muscle cell?

A

+20 mV, (at which point where Fast Na+ channels close)

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6
Q

What is the maximum membrane potential of the SA node?

A

0 mV

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7
Q

Sinoatrial (SA node) -

A

The pacemaker cell; it gives the greatest rhythmicity.

Has UNSTABLE resting membrane potentials, which makes it the “pacemaker”

IT DOES NOT HAVE Fast Na+ Channels

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8
Q

What are the 3 factors that act together to produce SA nodal Prepotential (pacemaker potential)?

A

1) Increased Na+ conductance/permeability at REST
2) Decreasing K+ conductance/permeability
3) Slow Ca2+ influx

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9
Q

Verapamil -

A

It inhibits Prepotential of the SA node by blocking Ca2+ channels, and inhibiting spontaneous pacemaker activity

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10
Q

Do AV nodes have Fast Na+ channels?

A

No, neither does the SA node

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11
Q

What are the 3 natural pacemakers of the human heart?

A

SA node
AV node
Purkinje Fiber (idioventricular pacemaker)

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12
Q

What are the firing rates of:
SA node
AV node
Purkinje Fiber

A

SA node: 60-100 times/ min
AV node: 40-55 times/min
Purkinje Fiber: 25-40 times/min

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13
Q

What are the major difference btw the 3 pacemakers of the human heart?

A

The rate of decay of K+ conductance during PHASE 4

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14
Q

What are the 3 ways you can change the firing rate of pacemaker cells?

A

1) change rate of Diastolic depolarization
2) change resting membrane potential
3) change threshold potential

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15
Q

What are the 3 ways to SLOW down the rate of firing of a Pacemaker cell?

A

1) lower the rate of depolarization
2) Hyperpolarize the cell
3) Change the threshold potential

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16
Q

How does the Sympathetic Nervous system change the slope of Pacemaker cells action potential?

A

It INCREASES the slope of the Prepotential, increasing HR

17
Q

How does the Parasympathetic Nervous system change the slope of Pacemaker cell action potential?

A

It DECREASES the slope, decreasing the HR

18
Q

Which system is used more, the Sympathetic nervous system or the Parasympathetic nervous system?

A

The Parasympathetic System.

The SA node is usually 100 beats/min, but the Parasympathetic system is always active, decreasing the SA node to 60-100 beats/min.

19
Q

List the order of the Conduction System of the Heart.

A
  1. Start at SA node
  2. Atrial Internodal Pathways
  3. AV node
  4. Bundle of His or AV bundle
  5. Bundle Branches
  6. Purkinje System
  7. Ventricular (heart) muscle
20
Q

What is the Conduction Velocity of the Atrial Internodal Pathway?

A

1 meter/sec

21
Q

What is the Conduction Velocity of the AV node?

A

0.02 meter/sec

22
Q

What is the Conduction Velocity of the Bundle of His/ AV bundle?

A

1-2 meter/sec

23
Q

What is the Conduction Velocity of the R/L Bundle Branches?

A

2-4 meter/sec

24
Q

What is the Conduction Velocity of the Purkinje System?

A

2-4 meter/sec

25
Q

What is the Conduction Velocity of the Ventricular (heart) Muscle?

A

0.3 meter/sec

26
Q

What controls the Conduction Velocity?

A

Fast Na+ Channels

27
Q

AN zone -

A

It is the transitional zone; cell types in this region are a mixture of Atrial and Nodal fibers interspersed w/ connective tissue

28
Q

N zone -

A

It is the Middle Portion of the AV node

29
Q

N-H zone -

A

It is the transitional zone; nodal fibers gradually merge w/ fibers from the Bundle of His.

30
Q

What controls the opening and closing of the Connexion gap channels?

A

pH and Ca2+ Concentration

31
Q

In order for Re-entry to occur, what 2 things must happen?

A

1) There must be a unidirectional block

2) The Refractory Period must be slower than propagation time around the loop

32
Q

An ECG/EKG is based off of what 3 suppositions?

A

1) The body is a conduction medium w/ the heart at the center
2) Heart depolarization generates a flow of ions throughout the extra cellular space of the body
3) Electrodes put on the body can detect ion flow

33
Q

What is the QRS complex?

A

It is when the Ventricular muscle depolarized, causing systolic contraction

34
Q

What is the T wave?

A

When the ventricle repolarizes and relaxes

35
Q

What is the P wave?

A

Atrial Depolarization, when the Atria undergoes systolic contraction

Physiology (9 decks)

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