Lecture 4 Test 4

Question 1

Anatomy of the heart layers

Answer 1

*Fibrous pericardium (leathery)
*Serous pericardium (parietal layer attached to fibrous pericardium)
*Serous pericardium (visceral layer/stretchy)
*Epicardium

Question 2

T/F: Purkinjie system has tons of fast sodium channels. The more fast sodium channels there are, the straight up the APs are.

Answer 2

True

Question 3

What kind of ions work best with gap junctions of the heart?

Answer 3

• Fast NA+ will cause a faster AP
• Ca++ is too big and will most likely cause a slower AP

Question 4

Downside of using gap junctions

Answer 4

Since it’s not a chemical synapse, it’s a bi directional synapse. Ectopic signals can cause unwanted APs to the heart cells that are not fully reset for another AP leading to problems.

Question 5

What can prevent unwanted APs or premature APs in our heart cells?

Answer 5

Our heart has guards in place such as Refractory period. (ex. If we’re in absolute refractory period, it won’t fire another AP).

Question 6

What happens if we have an AP while in relative refractory period?

Answer 6

Odd AP, it won’t look right and force generation won’t look right either.

Question 7

What is a frontal “coronal” plane EKG system

Answer 7

3-lead EKG setup ( + L arm. - R arm, + L foot)

Question 8

What does th aVR lead mean?

Answer 8

Augmented right lead

Question 9

What is the Mean electrical axis of the heart?

Answer 9

59 degrees towards the left foot

Question 10

What is the “eyeball” sensor?

Answer 10

The (+) electrode

Question 11

If the current is going towards the “eyeball”, what will you see?

Answer 11

a positive deflection

Question 12

If the current is going away from the “eyeball” you will see

big current moving away?

small current moving away from?

Answer 12

Negative deflection

Big negative deflection

Small negative deflection

Question 13

Which lead will show the best picture for the depolarization wave?

Answer 13

Lead II because the wave is heading directly towards it

Question 14

(3 lead EKG) Lead II

Answer 14

Eyeball (+) electrodes on the Left foot is looking at (-) electrode on right arm

Question 15

(3 led EKG) Lead III

Answer 15

Eyeball (+) electrode left foot is looking at (-) electrodes on left arm

Question 16

(3 lead EKG) Lead I
If the current is moving towards it? If it’s moving away?

Answer 16

Eyeball of left arm (+) lead is looking at the right arm (-) lead

Positive deflection, Negative deflection

Question 17

What is the name for 3 lead EKG?

Answer 17

Einthoven’s triangle

Question 18

What is the main depolarization wave?

Answer 18

towards left foot

Question 19

What is the purpose of the orientation of the 3 lead EKG?

Answer 19

To look at 60 degree angles of a unilateral triangle

Question 20

Who is Einthoven?

Answer 20

Deutsch scientist

Question 21

What is left axis deviation?

Answer 21

< 0 degrees, Depolarization is heading towards the left arm.
Lead I is in horizontal position
(heart rotated counter clockwise)

Question 22

What is right axis deviation?

Answer 22

> 90 degrees, Depolarization is heading towards the right side of the body
(heart rotated clockwise)

Question 23

Reasons that may cause heart deviations

Answer 23

Bundle branch block (may cause L or R deviations), COPD d/t big lungs full of air may cause the heart to be straight up and down. Breathing in and out may change the orientation of the heart. Pathophysiology of the heart may deviate d/t unilateral size.

Question 24

For our class, what is considered Left or Right axis deviation?

Answer 24

Anything off of 59 degrees, L (anything less than 59 degrees), Right (anything more than 59 degrees).

Question 25

Are the walls of the heart the same size?

Answer 25

No, the left wall is thicker due to pumping pressures more than the right.

Question 26

How is depolarization spread throughout the heart?

Answer 26

Endocardium to epicardium

Question 27

How does the repolarization of the atrium look in the EKG?

Answer 27

Since it's going the opposite direction, it would be a neg deflection but since the walls are thin compared to the left ventricle, you don't see it behind the QRS complex.

Question 28

Einthoven's law: deflection magnitude.

Answer 28

Lead I + Lead III = Lead II First remove the negative from the positive.

Question 29

How can you check how much smaller is the positive deflection of Lead I is compared to Lead II?

Answer 29

You'd have to figure out how much current is moving from the Pts right to the left by putting a perpendicular line from the lead II arrow and up to the lead I horizontal line. Side A < side H (voltage is 1.5mV) = Ex. 0.6mV

Question 30

The amount of right to left current we have dictates ....

Answer 30

how much current we have in Lead I

Question 31

What happens if our Mean Axis is 90 degrees (straight up and down), what is the current for Lead I? Lead II?

Answer 31

It would be 0, no current running. Large positive net deflection

Question 32

What if we have a Mean axis pointed towards the right side of the body/foot?

Answer 32

We would have a net negative on Lead I

Question 33

What can you diagnose with a 3 lead EKG?

Answer 33

Any electrical problem, depending on the angle of deflection and may need more chest leads (eyeballs)

Question 34

What happens when there's 50% depolarized and 50% repolarized?

Answer 34

Larger magnitude of deflection for Lead I, II, III d/t more current flowing

Question 35

What happens when 75% of ventricle is depolarized?

Answer 35

Slightly smaller magnitude of deflection in leads I, II, III compared to 50% depolarized

Question 36

What happens when about 90% of ventricles are depolarized?

Answer 36

Negative deflection in Leads II and III. Positive deflection in Lead I (R>L movement).

Question 37

What happens when 100% of ventricles are depolarized?

Answer 37

No current = Zero deflection in all leads