Lecture 3 Test 4

Question 1

When looking at the electrode meter, if you’re moving away from the + electrode (repolarize), you will see

Answer 1

A negative deflection on the meter

Question 2

When looking at the electrode meter, if you’re towards the + electrode (depolarization), you will see

Answer 2

A positive deflection on the meter

Question 3

Compare Action potentials in the ventricles depolarization vs repolarization

Answer 3

-Depolarization (current flow is neg>pos) shows as a positive deflection.

-Repolarization (current flow is pos>neg) shows as a positive deflection.

aka double negative.

Question 4

Why is T wave a positive deflection?

Answer 4

Because the repolarization current flow is going from pos>neg = positive deflection.

Question 5

What causes a negative deflection on the t wave?

Answer 5

If the current flow is neg>pos = negative deflection

Question 6

What phase is resting membrane potential?

Answer 6

Phase 4

Question 7

Fast action potential to phase 4 looks like……

Answer 7

a little slope because not much HCN, leak Na+, or Ca++ at the moment.

Question 8

Will there be a spontaneous AP that can occur in your heart?

Answer 8

It could if you give it enough time.

Question 9

What’s another name for phase 4 (nodal area)?

Answer 9

-Diastolic depolarization
-Phase 4 depolarization

Question 10

The faster the rate of diastolic depolarization leads to a….

Answer 10

faster AP to increase hr.

Question 11

Phase 0 in the nodal area

Answer 11

Upstroke of AP. compared to other AP that go straight up (fast Na+ ch), in a heart AP (nodal area), its more of a slope

Uses L type Ca++ ch (slow to open and close) = extended time

Question 12

What happens if there’s a really fast AP that occurs in the heart leading to a fast and high slope?

Answer 12

The AP get propagated to the next cell and entails Na current in the ventricle. Depolarization occurs in the area where Na channels came in and move through gap junctions to their neighbor.

Question 13

What determines how fast of the AP moves around the heart?

Answer 13

The slope of phase 0

Question 14

Phase 0 is affected by which specific ion?

Answer 14

Ca++; big and clunky and slow influx maybe r/t slow AP.

Question 15

What phase is repolarization in the heart?

Answer 15

Phase 3

Question 16

L-type channel closing, VG K+ channels open in what phase?

Answer 16

Phase 3

Question 17

Is there a phase 2 in the nodal area?

Answer 17

Most often not. but if there is, it’s the plateau phase d/t slow L type ca++

Question 18

SA node Vrm

Threshold mV

Answer 18

-55 mV

-40 mV

Question 19

Is aV node the same as SA node AP?

Answer 19

No, it is not as leaky to Na+, Ca++ in phase 4

Question 20

AV node phase 4 and Vrm

Answer 20

more negative, longer to generate an AP

Question 21

Where in the heart can you find HCN channels?

Answer 21

More in the SA node and some in AV node and the rest of the ventricles.

Question 22

Why does the inside of the heart AP longer than the outside of the heart?

Answer 22

It causes the endocardium and epicardium to have an AP at the same time > endocardium is depolarizing while epicardium is depolarizing > simultaneous contraction > stronger heartbeat to pump blood

Question 23

Does the atria have long/extended APs?

Answer 23

No, it doesn’t need it because its muscle walls are thin and works with less pressures.

Question 24

Where are the PNS attachments in the heart?

Answer 24

Vagus attachments are more concentrated at the nodal areas

Question 25

Where are the SNS attachments in the heart?

Answer 25

The attachments are widespread throughout the heart (ventricles, atria, nodal tissues)

Question 26

Resting hr (healthy heart/patient)

Answer 26

72bpm

Question 27

60 secs / (0.83 secs) RR int = HR

Answer 27

= 72bpm

Question 28

- If the SA node (PNS) had no inputs anywhere else, it would generate APs at a rate of? - SNS can add how many more bpm?

Answer 28

110 bpm SNS ( adds 10 bpm) = 120 bpm

Question 29

which has more input on the conduction system? PNS or SNS?

Answer 29

PNS

Question 30

SNS can add how many more bpm?

Answer 30

10 bpm

Question 31

PNS can generate how many bpm?

Answer 31

110 bpm

Question 32

If you just have Vagal tone, you have approx. how many bpm?

Answer 32

60-62 bpm

Question 33

Generates how many bpm? -SA node -AV node -Purkinjie system

Answer 33

72 bpm 40-60 bpm 15-30 bpm

Question 34

What are the 3 internodal pathways for the right atria? (between the SA and AV nodes)

Answer 34

Anterior Middle Posterior

Question 35

What does the anterior internodal pathway control? What's another name for this?

Answer 35

Electrical system of the Left atrium aka Interatrial bundle "Bachman's bundle"

Question 36

How long does the AP take to get from SA node to AV node?

Answer 36

0.03 (3 hundredths) of a seconds

Question 37

How long does it take for the right atria to depolarize?

Answer 37

0.07 (7 hundredths) of a second

Question 38

How long does it take for the left atria to depolarize? What does this depict on the cardiac rhythm strip?

Answer 38

0.09 (9 hundredths) of a second -P wave duration

Question 39

What does Dr. Schmidt mean by top half?

Answer 39

bilateral atrias and SA/AV nodes

Question 40

How long does it take for the AP to reach from the SA node all the way to the tip of the purkinjie fibers? Basically the whole heart.

Answer 40

Ideally 0.22 secs (22 hundredths) Maybe longer for older, sick patients

Question 41

Why is there a 0.2 secs delay at the AV node?

Answer 41

Gives the atria time to contract and fill the ventricles

Question 42

Other functions of the AV nodes

Answer 42

Filters extraneous AP from the SA node that may lead to fast ventricular conductions

Question 43

Does the AV nodes have gap junctions within its cells?

Answer 43

Very little, that's why APs take longer to pass through; hence, the delay

Question 44

How long is the delay in the AV node? Delay in the bundle of his? Total AP time from SA node down to the Left/right bundle branch?

Answer 44

0.12 secs 0.01 secs Total 0.13 secs (AV delay) + 0.03 secs (SA to AV) Total 0.16 secs (PR interval)

Question 45

Other ways the AV node acts as a filter

Answer 45

ex. Abnormally fast APs from the atria that may hit the AV node while in refractory period. Protects us from causing ventricular tachyarrhythmias

Question 46

What is the general pattern of the electrical signals

Answer 46

Going towards the left foot

Question 47

If we put a (+) electrode on the left foot and (-) electrode to the right arm what would we see on a meter?

Answer 47

A big positive deflection during depolarization. The magnitude depends on how much tissue still remaining to depolarize

Question 48

When do you have the biggest current in the magnitude of deflection?

Answer 48

Its when you have half depolarized and half depolarized.

Question 49

How many degrees is the angle of electrical signals from right arm to left foot?

Answer 49

59 degrees is the average electrical movement (59 degrees lower than horizontal)

Question 50

What do we measure in the EKG

Answer 50

All of the APs in the heart

Question 51

EKG magnitude of depolarization is approx.

Answer 51

100mV

Question 52

QRS magnitude of deflection when leads are on the limbs when its closer to the heart (ex. chest leads) magnitude of deflection are around...

Answer 52

+1.5mV + 3 - 4mV

Question 53

What causes the lower readings of magnitude of deflection through the electrodes?

Answer 53

Things in the way such as air in the lungs since electricity doesn't travel through air

Question 54

QT interval is the...

Answer 54

length of time for ventricle depolarization

Question 55

Normal P wave size on egg strip

Answer 55

2.5 boxes height x 2.5 boxes width (positive deflection - > +)

Question 56

What does it mean if the P wave is high?

Answer 56

Right Atrial hypertrophy

Question 57

What does it mean if the P wave is too long?

Answer 57

Long conduction maybe due to a left atrium being stretched out

Question 58

What does it mean if there's a double hump on the P wave?

Answer 58

Possible electrical block

Question 59

What is a Q wave

Answer 59

negative deflection before the R wave

Question 60

What is the R wave?

Answer 60

Positive deflection

Question 61

T/F: Not everyone has a Q wave that's why it's called PR interval not QR int

Answer 61

True

Question 62

Normal PR interval

Answer 62

0.16 secs

Question 63

Total heart depolarization 0.22 minus total depolarization from SA node to the tip of bundle branch 0.16 is

Answer 63

QRS complex of 0.06 secs (ideally) Normally longer

Question 64

Normal height deflection of QRS complex (total electrical activity)

Answer 64

Typically +1.5 mV (5 large boxes)

Question 65

Reasons why a QRS complex can be super large

Answer 65

Electrodes are really close to the heart, Heart tissue is massive, enlarged ventricular tissue.

Question 66

Cardiomyopathy

Answer 66

Prolonged QRS and longer depolarization

Question 67

Can you see the atrial repolarization on a EKG?

Answer 67

No, it's usually hidden behind the QRS wave

Question 68

When do you know if all of the ventricular process has been depolarized?

Answer 68

at the end of the QRS aka" J-point" or "Isoelectric point"

Question 69

Area between the end of T wave and beginning of P wave should be?

Answer 69

Flat; meaning the healthy heart tissue should be at rest. If there's movement = unhealthy heart tissues

Question 70

Where in the EKG can you find if there are unhealthy ventricle tissues and why?

Answer 70

Between the end of S wave and T wave (should be flat), low in nutrients unable to repolarize causing abnormal tracings of depolarization. (elevated/depressed ST segments)

Question 71

What is the QT interval? Normal time for QT interval?

Answer 71

start of ventricle depolarization and end of repolarization. 0.25 - 0.35 secs (duration of endocardium fast APs)

Question 72

Repolarization of the ventricle is labeled as

Answer 72

T wave (positive deflection)

Question 73

If we need to make our hr faster d/t activity the heart will

Answer 73

shorten the QT interval to make an AP happen quicker

Question 74

What is Lusitropy?

Answer 74

Depolarizes/resetting the ventricle faster than it normally does.

Question 75

What can you give to make the heart repolarize quicker and eventually increase HR?

Answer 75

a positive Lusitropic agent.

Question 76

Define: Inotropy Chronotropy Dromotropy Lusitropy

Answer 76

- Stronger heart contraction/beat (more Ca++ influx) - Increase heart rate - Speed of conduction (electrical impulse d/t NA+ current) - Resetting of the heart during an AP

Question 77

Calculate hr with RR int: normal hr = 60 secs / 0.83 secs (RR interval)

Answer 77

72 bpm

Question 78

Each big box is about how many mV?

Answer 78

0.5 mV

Question 79

Each big box is divided by?

Answer 79

5 small boxes = 0.04secs/small box

Question 80

Cardiac rhythm strips are fed through the machine at a rate of?

Answer 80

25 mm/sec

Question 81

How many big boxes in a 1 sec strip? How many secs per big box? How many secs per small box?

Answer 81

5 big boxes 0.2 secs 0.04 secs

Question 82

What is a refractory period?

Answer 82

resetting of the heart after an AP

Question 83

What is a relative refractory period?

Answer 83

It's when the cell is not fully reset before another AP or else result with a weaker conduction (early premature contraction)

Question 84

What happens in the absolute refractory period?

Answer 84

The heart will not be able to fully reset and unable to elicit an AP.

Question 85

What is the most important for the hearts potential?

Answer 85

Coordination and timing!