Karius: Cardiac Cycle and Normal ECG ibook notes

Question 1

Fast action potentials are found where

Answer 1

atrial and ventricular

Question 2

Slow action potentials are found

Answer 2

in the SA and AV nodes

Question 3

Fast action potential phase 0:

Answer 3

rapid upsweep (depolarization)

voltage gated Na channels open and the cell is rapidly depolarizing

same as skeletal muscle

Question 4

Fast action potential phase 1:

Answer 4

occurs around +20 mV

Initial repolarization

sodium channels inactivate so no more sodium enters; voltage gated potassium channels open

Question 5

Fast action potential phase 2:

Answer 5

plateau

“slow voltage gated calcium channels opening” AND “special voltage gated K channels closing”

Question 6

Fast action potential phase 3:

Answer 6

Repolarization, Slow Ca channels closing and special K channels opening

Question 7

Fast action potential phase 4:

Answer 7

resting potential sustained by high potassium conductance

around -85 mV

Question 8

SA node and AV node AP: phase 4

Answer 8

resting membrane potential is NOT isotonic, gradually increases (depolarizes) until threshold value achieved and SA first; this is due to the funny Na voltage gated channels. (Na channels open during repolarization)

this is an intrinsic spontaneous event

AV node has same thing but phase 4 is much slower, normally doesnt reach threshhold value before being stimulated by an action potential originating in the SA node

Question 9

SA node and AV node AP: phase 0

Answer 9

due to opening of slow Ca gates and closing of special K gates

same for AV node

Question 10

SA node and AV node AP: phase 3

Answer 10

remember: no 1 or 2 phase, goes from 0 to 3

Question 11

Normal EKG: P wave

Answer 11

atrial contraction

Question 12

Normal EKG: QRS wave

Answer 12

ventricular contraction

Question 13

Normal EKG: T wave

Answer 13

ventricular repolarization

Question 14

PR interval

Answer 14

starts at beginning of P wave and ends at beginning of QRS complex

AV nodal delay time.

represents time it takes to pass from atria to the ventricles via the AV node: this is incorrect I believe

Question 15

ST wave

Answer 15

begins at end of QRS, ends at beginning of T

Question 16

QR interval:

Answer 16

begins with beginning of the QRS complex and ends at the end of the T wave, so it includes two waves

QRS and T wave

represents total time any ventricular myocite is depolarized

Question 17

beginning of P wave and the cardiac cycle

Answer 17

both atria and ventricles are in diastole
all voltage gated channels are closed except for leaky K and Na/K ATPase

SA and AV nodes in P4, with funny Na channels operating (pre-potential)

AV has fewer funny channels so its pre-potential is slower to develop

Tricuspid and Bicuspid are open

Aortic and pulmonic are closed

Question 18

pressure of left and right atrium during diastole

Answer 18

diastolic mmHG is usually 4 mmHg

Question 19

pressure in left and right ventricles during diastole

Answer 19

0 mmHg

pressure in ventricle must be less than in atria for blood to flow

Question 20

Pulmonary artery pressure diastole

Answer 20

15 mmHg

Question 21

Aorta pressure diastole

Answer 21

80 mmHg

Question 22

how will diastole pressure be effected if resistance in the arteries is high?

Answer 22

diastolic pressure will be higher

Question 23

how will diastole pressure be effected if resistance in the arteries is low?

Answer 23

diastolic pressure will be lower

Question 24

Jugular Vein: why is this sensitive to blood flow changes?

Answer 24

there are no valves between the atria and the veins

changes in atria; pressure will effect venous return

Question 25

Atrial contraction: wave, pressure direction, direction of blood, and ventricular pressure

Answer 25

P wave from atria into ventricles ventricular pressure increases as well

Question 26

Why doesnt the ventricle contract before the atria?

Answer 26

the AV has a slow ventricular depolarization to allow for blood to fill

Question 27

What is the normal pressure of the ventricles at their height of contraction?

Answer 27

around 120 mmHg, on the left side

Question 28

During the ___ wave the left ventricular pressure begins to increase.

Answer 28

P wave

Question 29

During the QR phase, the left ventricle pressure

Answer 29

decreases for a moment and then increases,

Question 30

the mitral valves open at _____ wave

Answer 30

the pinnacle of the R wave

Question 31

Left ventricular pressure goes _______ during RS phase

Answer 31

WAY up, very steep increase: the aortic valve is closed during this period, hence the pressure build up

Question 32

the ST line corresponds roughly with the ventricular pressure diagram. What is the character of the pressure?

Answer 32

pressure increases in the left ventricle from the pinnacle of the R wave to the very beginning of the T wave. it increases just a bit more and then decreases mostly during the T wave

Question 33

the aortic valves close near the ____ point on the EKG

Answer 33

right after the T wave (repolarization)

Question 34

the mitral valve opens during what part of the EKG?

Answer 34

inbetween the T and P waves (during the isoelectrical period)

Question 35

The first heart sound (S1) occurs immediately

Answer 35

after the AV valves close: blood suddenly hits the closed valve/cardiac structure (now closed) making the first "lub" sound S1 is the loudest sound

Question 36

What waves are you going to count to determine the net deflection in the limb leads?

Answer 36

QRS

Question 37

What waves are you going to count to determine the net deflection in the limb leads?

Answer 37

QRS

Question 38

What waves are you going to count to determine the net deflection in the limb leads?

Answer 38

QRS

Question 39

Inferior leads =

Answer 39

II, III, AVF

Question 40

What waves are you going to count to determine the net deflection in the limb leads?

Answer 40

QRS

Question 41

Inferior leads =

Answer 41

II, III, AVF

Question 42

What waves are you going to count to determine the net deflection in the limb leads?

Answer 42

QRS

Question 43

Inferior leads =

Answer 43

II, III, AVF

Question 44

What waves are you going to count to determine the net deflection in the limb leads?

Answer 44

QRS

Question 45

Inferior leads =

Answer 45

II, III, AVF

Question 46

What waves are you going to count to determine the net deflection in the limb leads?

Answer 46

QRS

Question 47

Inferior leads =

Answer 47

II, III, AVF

Question 48

what does the PR interval indicate?

Answer 48

no voltage difference between the atria

Question 49

what direction does the SA node depolarize the atria?

Answer 49

Right to Left

Question 50

segment refers to

Answer 50

a single event on an ECG

Question 51

interval refers to

Answer 51

several events on an ECG

Question 52

In what phase of an atrial or ventricular action potential do you find the voltage gated potassium channels, and what kind of voltage opens them?

Answer 52

phase 1: they open during depolarization

Question 53

In what phase of an atrial or ventricular action potential do you find the timed gated potassium channels, and what kind of voltage opens them?

Answer 53

phase 3 stays closed during phase 2 and then helps open during phase 3. the T wave represents depolarization of ventricular myocytes the timed gated potassium channels are found during the 2nd phase and they are voltage gated, but they close during depolarization, and stay closed for a finite amount of time

Question 54

what phase on the ECG is represented by phase 0?

Answer 54

P wave and QRS respectively

Question 55

PR segment vs PR interval

Answer 55

PR interval represents the beginning of P wave until beginning of QRS: how long does the signal take to geth through the AV node PR segment represents the end of atrial depolarization until beginning of QRS-

Question 56

QT interval is largely controlled by what gates?

Answer 56

timed potassium gates

Question 57

what is responsible for controllign plateau phase?

Answer 57

closing of potassium gates and opening of calcium gates

Question 58

Inferior leads =

Answer 58

II, III, AVF, R. coronary artery

Question 59

septal regions =

Answer 59

V2 and V3

Question 60

anterior region of the heart region =

Answer 60

V2, V3, V4

Question 61

Lateral heart

Answer 61

I, AVL, V4,V5, V6