Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

HOS Unit 2 > 16 Cardiac electrophysiology > Flashcards

16 Cardiac electrophysiology Flashcards

0
Q

In which part of the heart do perkinji fibers lie?

A

In the endocardium

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
1
Q

What does phospholamban do?

A

-Phosphorylating phospholamban (PLB) relieves its inhibition on the SR Ca++ pump in cardiac muscle, thus resulting in weaker contraction due to less Ca++ in the cytoplasm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which part of the heart is the last area to depolarize during systole?

A

The epicardium at the base. (this would be in the ventricle)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

The route of electrical impulse through the heart?

A

SA node, through atria, AV node (delay), bundle of His, left and right bundle branches, perkinji fibers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

which area of the heart is the pacemaker?

A

the SA node

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is the internodal pathway?

A

They use it to explain the route through the atria form SA to AV node.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the only electrical conduction pathway between the atria and the ventricles?

A

The AV node.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

Which heart cells have the fastest conduction rate?

A

Purkinji fibers at 4 M/S

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What makes the perkinji fibers the fastest conducting cells in the heart?

A

Large diameter

Large number of Na+ channels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

T/F the electrical impulse of the heart spreads from epicardium to endocardium?

A

False, Because the perkinji fibers are in the endocardium, it spreads from inside out; or endocardium to epicardium.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does digitalis do? What is another name for digitalis?

A

Inhibits the Na/K+ pump, and its also known as digoxin.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which ion in the cell sets the resting membrane potential? How does it do it?

A

K+

It is because it is the leakiest.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

The outward directed K+ leak current is primarily due to what?

A

The inward rectifier Ik (Ikir) chanel

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

About how much K+ needs to leak out of the cell to establish the resting membrane potential?

A

Very little. (0.004% of intracellular K+)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the concentration of sodium on the inside of a cell? on the ouside?

A

inside= 10 mm (mm is milimolar)

outside=145 mm

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is the concentration of K+ on the inside of a cell? on the outside?

A 
inside= 120 mm
outside= 4.5 mm
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Review the Na+ channel.

A

Impulse, quick activation gate (initially closed) but also slow inactivation gate started at threshold, open then becomes closed, absolute refractory period, relative refractory period.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the isoelectric/gradient point in a cell for Na+?

A

+60 This means that if it gets to +60, sodium would no longer want to have a net influx.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

In cardiomyocytes, what causes phase 0?

A

Influx of Na+ and Ca+ which causes depolarization.

recall that cardiomyocytes have fast action potentials

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What causes phase 1 in cardiomyocytes?

A

The closure of fast Na+ channels. This causes a slight repolarization drop.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what causes phase 2 in the cardiomyocyte?

A

2 Parts;

a) T- type Ca+ channels inactivate rapidly lowering the peak.
b) L- Type Ca+ channels inactivate slowly causing the plateau of phase 2

21
Q

What causes phase 3 in the cardiomyocyte?

A

influx of K+. (The K+ channels are slow but is causes repolarization through the delayed rectifier K+ channels)

22
Q

What causes phase 4 in the cardiomyocyte? what does phase 4 look like?

A

Phase 4 is maintained by the K+ leak channels at a constant resting membrane potential of about -80mv.
The line on the graph is the horizontal line.

23
Q

So, what causes the plateau in the cardiomyocyte action potential?

A

the slow closing L-type Ca+ channels

24
Q

The SA node and AV node have fast of slow action potentials?

A

Slow.

25
Q

What causes phase 0 in the SA node?

A

Ca+ influx only! These cells do not have Na+ channels.

26
Q

what causes phase 1 and 2 in SA nodal cells?

A

Trick question because these phases do not exist in slow type action potentials.

27
Q

what causes phase 3 in the SA node?

A

opening of the K+ channels and closing of the Ca+ channels

28
Q

what causes phase 4 in the SA node?

A

If (funny channels)
ICa+ (calcium flows into cells more)
IK+ (slowly becomes less leaky)

29
Q

What effect does Cl- have on the action potential of the SA node?

A

Very little for our purposes so just ignore it. (it would move into the cell slowly though)

30
Q

What does phase 4 of a SA node look like on the graph?

A

A positive slope. This is because funny channels allow cations to move in, Ca+ becomes more permeable, and the K+ leak channels become less leaky.

31
Q

what do funny channels do?

A

they have a slow inward cation current that starts once the cell reaches hyperpolarization. Causes the cell to become a little bit more + and closer to threshold.

32
Q

what is the threshold potential for slow action potentials? fast action potentials?

A

slow=-35mv

fast=-65 mv

33
Q

what is the conduction velocity of slow action potentials? fast action potentials?

A

slow velocity= .1 m/s

fast velocity= 3 m/s

34
Q

what phase of slow action potential do you see the opening of the Na+ channels?

A

None! these do not have Na+ channels. Just a reminder.

35
Q

what will be the result of decreasing the slope of phase 4 in the slow action potential?

A

a slower heart rate.

36
Q

what would be the result of increasing (more +) the threshold of a slow action potential in the SA node?

A

slow heart rate. this is because it would take a little bit longer to reach the value.

37
Q

what would be the effect of hyperpolarizing the slow action potential in the SA node?

A

slower heart rate. This is because it takes more time to reach the regular -35 mv if your more negative.

38
Q

Normal rate of depolarization for SA node? AV node? cardiomyocytes?

A

1) 60-100 bpm
2) 40-50 bpm
3) 40 bpm

39
Q

What does an EKG pick up?

A

current that is moving on the outside of the cell. This will be opposite of the inside movement.

40
Q

How do you calculate conduction velocity? (the equation)

A

(conduction velocity)=change in voltage/resistance (also said as V=IR)

41
Q

what 2 things cause a change in voltage in the V=IR equation?

A

amplitude (resting to action potential height)

slope (of the action potential such as in phase 4)

42
Q

what effect would increasing K+ concentrations outside to cell do?

A

slow action potentials. If too much was outside, an action potential would not fire.

43
Q

T/F If you have enough gap junctions, you have nearly zero resistance?

A

true

44
Q

T/F larger muscle fibers have less resistance?

A

true

45
Q

What does the action potential look like during phase 0 of a cardiomyocyte if it contracts during the relative refractory period?

A

The normal straight up line now has a slight slope. This is because there are many Na+ channels that are still closed.

46
Q

which cells have the largest diameter in the heart?

A

1) purkinji cells and HIS bundle cells (50 micro m.)
2) atrial and ventricular myocytes (12 micro m.)
3) SA and AV nodal cells (7 micoro m.)

47
Q

which heart cells conduct the fastest?

A

Purkinji and His bundle cells followed by cardiomyocytes, followed by SA and AV nodal cells.

48
Q

what are the shapes of nodal cells? ventricular myocytes? purkinji cells?

A

nodal cells= round, ovoid
myocytes= cylindrical
purkinji cells= cylindrical

49
Q

which cells in the heart conduct the fastest? slowest?

A 
fastest= purkinji cells
slowest= nodal cells.
50
Q

What activates the funny channels during phase 4?

A

Hyper polarization

51
Q

what is the concentration of Ca+ on the side of a cell? on the outside?

A

inside=.0001 mm

outside= 1.0 mm

HOS Unit 2 (21 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions