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Flashcards in Cardiovascular Deck (71):
1

What is the ability of a cell to respond to an external electrical stimulus, usually in the form of an action potential?

Excitability

2

What is the ability for a cell or a group of cells to initiate an action potential?

Automaticity

3

What is the ability of a cell or region of cells to receive and transmit an action potential?

Conductivity

4

What is the **inability** of a cell to receive and transmit an action potential?

Refractoriness

5

What is the ability of cells to alter the rate of electrical conduction?

Dromotropism

6

Why is it that the SA node is the pacemaker part of the heart, and not the AV node?

SA node is faster

7

Why is it that potassium channel blockers prolong the QRS complex?

Prevent the K channels from releasing K to balance out Ca that has rushed into the cell

8

True or false: the electrical activity always precedes the mechanical activity

True

9

What does the P wave represent?

Depolarization of the AV node

10

What does the Q wave represent?

***

11

What does the R wave represent?

***

12

What does the S wave represent?

***

13

What does the T wave represent?

Repolarization of the ventricles

14

Where is the EKG line of repolarization of the atria?

Hidden in the QRS complex

15

What allows for the spontaneous depolarization of phase 4 in the SA and AV nodes?

Funny channel If (Leaky Na channels)

16

What causes the initial depolarization of the AV node? (phase 0)

Opening of Na channels (influx)

17

What causes the prolonged phase 2 in the AV node?

influx of Ca and efflux of K

18

Draw the phases of the AV node AP.

Draw

19

What is responsible for the phase 3 repolarization of the AV node?

Ca channels close, K continues to leak out

20

What are the two types of Ca channels? When do they open?

L type (long)
T type (transient)

Both open at beginning of phase 1

21

What is the ion exchange that is occurring in phase 2?

Ca goes in, K goes out

22

What happens with the ion exchange in phase 3 of the AP?

Ca stops

K continues to efflux to balance out charges

23

What is the channel that is responsible for the upward depolarization in phase 4?

Funny Na Channel

24

What are the three phases of the Na channels?

1. Activation gate closed
2. Gates opened
3. Inactivation gate closed (repeat)

25

What happens in phase 3 of the cardiac myocytes?

Ca channels close
K continues to leak out

26

What is responsible for the phase 4 current in the AV/SA node?

If (funny Na channel)

27

True or false: the Na channels have two gates, which respond in the same way to depolarization

False--respond in opposite ways

28

What is the resting state of the Na channels? What happens when depolarization occurs?

Activation gate closed, inactivation gate open


Rapid opening of the activation gate

29

What happens when the activation gate on Na channels open in response to depolarization?

Inactivation gate closes

30

What happens to Na channels when repolarization occurs?

First, activation gate closes, then inactivation gate opens

31

What happens when you block the opening of the activation gate? Relate this to the phases of depolarization.

Prolong Na intake, prolong phase 0

32

What happens when you block the inactivation state of Na channels?

Shorten AP

33

What happens when there is an enhanced late I(Na)? Relate this to Ca levels.

prolonged depolarization of Na, causes more Na to enter. NCX transporter also causes increased intracellular Ca, leading to cellular instability/mechanical dysfunction

34

What are the 4 cardiovascular conditions that are caused by increased late I(Na) channel closing?

1. Ischemic heart disease (angina)
2. Heart failure
3. Arrhythmias
4. PAD/claudication

35

What are the two neurological disorders that are caused by increased late I(Na) channel closing?

Szs
Neuropathic pain/muscle paralysis

36

Draw out the SA/AV node depolarization curve vs the ventricular muscle fiber depolarization curve.

Draw

37

What is responsible for phase 0 depolarization of the SA node?

Ca influx

38

What is responsible for phase 0 depolarization in ventricular muscle fibers?

Na influx

39

What is the main ion change that is occurring in phase 3 of the nodal depolarization curve?

K efflux

40

What is the main ion change that is occurring in phase 4 of the nodal depolarization curve?

Na influx

41

What is the main ion change that is occurring in phase 1 of the ventricular muscle depolarization curve?

K efflux

42

What is the main ion change that is occurring in phase 2 of the ventricular muscle depolarization curve?

Ca influx
K efflux

43

What is the main ion change that is occurring in phase 3 of the ventricular muscle depolarization curve?

K efflux

44

What is the effect of blocking Ca influx on the nodal cell?

Decrease in automaticity

45

What is the effect of blocking Na on ventricular muscle fibers?

Decrease in phase 0 depolarization

46

What is the effective refractory period?

the period in which the tissue will not respond to any additional stimulus

47

What does the ERP/APD ratio determine?

the ability of abnormal impulses to depolarize the tissues

48

What is the relative refractory period?

time after the effective refractory period in which it is difficult, but not impossible, to generate an action potential

49

A lower ERP/APR ratio means what?

easier to depolarize

50

What does the SANS affect on cardiac function?

SA node
AV node
ventricular myocardium
Atria
His-Purkinje system

51

What does the PANS affect on the cardiac function?

vagal nerve
SA/AV nodes
atrial/ventricular myocardium

52

What happens in sinus node tachycardia?

Increase in the depolarization of the sinus node and increased conduction velocity

53

What does SA node tachycardia look like on an EKG?

Increased rate

54

What is the pathophysiology of atrial tachycardia?

Ectopic foci in the atria cause depolarization,

55

How does atrial tachycardia present on an EKG?

P waves without QRS complex

56

What are early afterdepolarizations?

Depolarizations that occur before the total repolarization of the ventricular muscle.

57

What are "triggered activities"?

Abnormal upstrokes that occur after a normal upstroke

58

What metabolic disturbance can result in early after depolarizations?

Hypokalemia

59

EADs are induced more readily in what part of the heart?

Purkinje cells

60

What is torsades de pointes?

QRS complex occurs when a P wave is supposed to happen, triggering a ventricular fibrillation

61

What does a U wave represent?

Depolarization of papillary muscle

62

What are delayed after depolarizations?

Ca overload (secondary to some condition) causes a depolarization after the normal depolarization, which can generate aberrant beats if it reaches threshold

63

What is the EKG of a first degree block?

Increased PR

64

What is the EKG of a second degree AV block?

Not all P waves pass (followed by a QRS complex)

65

What is the EKG of a third degree block?

no P/QRS relationship

66

What is the cause of reentry?

Existence of conduction routes with different conduction velocities

67

What is AV node reentrant tachycardia?

Two different conduction pathways in the AV node with different conduction speeds. A premature beat causes circus motion between the loops

68

P waves that come after the QRS complex = ?

Accessory pathway mediated SVT

69

Atrial flutter is caused by what?

Reentry circuit

70

What does the EKG of a ventricular reentry look like?

Huge QRS complexes

71

What is the difference between sinus tachy/bradycardia and atrial flutter/fibrillation?

Sinus atrial and ventricular rate =

A-fib/flutter has different ventricular and atrial rates