EKG basics

Question 1

what is true of myocytes

Answer 1

polarized at rest
inside is negatively charged compared to out
membrane pumps (control ion distribution) necessary to keep inside electronegative

Question 2

what is needed to keep cell polarized (in this state)

Answer 2

ATP

Question 3

Na K pump moves how many ions?

Answer 3

3 Na out

2 K in

Question 4

how do cardiac cells lose their internal negativity?

Answer 4

depolarization

Question 5

how many types of cells in the heart?

Answer 5

1. pacemaker cells - power
2. electrical conducting cells - wiring
3. myocardial cells - contraction

Question 6

what is true of pacemaker cells

Answer 6

innate electrical characteristics
input from nerual and hormonal
serve as a source of a wave of depolarization

Question 7

what are the phases of action potential

Answer 7

phase 0 - rapid Na influx 
phase 1 - K & Cl efflux
phase 2 - Ca influx K efflux
phase 3 - K efflux
phase 4 - K influx

Question 8

what is automaticity?

Answer 8

all heart cells possess ability to behave as a pacemaker. Suppressed unless SA node fails

Question 9

What is rate of of sites?

Answer 9

sa - 60-100 / min
av - 40 - 60
bundle 30 - 40
perk. 30 - 40

Question 10

what is excitation- contraction coupling?

Answer 10

Actin and Myosin and when a wave of depolarization reaches a myocardial cell, calcium is released within the cell, causing the cell to contract.

Question 11

True or false: Myocardial cells CAN transmit electrical current like conducting cells

Answer 11

true

Question 12

what is time and length of small squares?

Answer 12

1 mm

0.04 s

Question 13

what is time and length of big squares?

Answer 13

5 mm

0.2 s

Question 14

verticle axis = voltage

Answer 14

small square - 0.1 mV

big square - 0.5 mV

Question 15

what does PR interval represent?

Answer 15

start of atrial depolarization to start of ventricular depolarization.

Question 16

What does ST segment represent?

Answer 16

Measures time from the end of ventricular depolarization to the start of ventricular repolarization

Question 17

What does QT segment represent?

Answer 17

Measures time from beginning of ventricular depolarization to the end of ventricular repolarization.

Question 18

how does a biphasic wave come about?

Answer 18

depolarizing wave moving perpendicular to a positve electrode

Question 19

12 lead ECG consists of what types of leads?

Answer 19

6 limb (3 standard 3 augmented)
6 precordial

Question 20

what are the signs on lead 1

Answer 20

right arm ( – ) left arm( +)

Question 21

what are the signs on lead 2

Answer 21

right arm ( –) legs( +)

Question 22

what are the signs on lead 3

Answer 22

left arm (–) legs( +)

Question 23

what is true of precordial leads?

Answer 23

illustrate horizontal plane

all electrodes are (+) with (-) central terminal

Question 24

what are positions for precordial electrodes?

Answer 24

V1 – 4th intercostal space to right of sternum
V2 – 4th intercostal space to left of sternum
V3 – between V2 and V4
V4 – 5th intercostal space in midclavicular line
V5 – 5th intercostal space at anterior axillary line
V6 – 5th intercostal space in midaxillary line

Question 25

Which leads allow you to see anterior view

Answer 25

V1, V2, V3, V4

Question 26

Which leads allow you to see left lateral view

Answer 26

I, AVL, V5, V6

Question 27

Which leads allow you to see inferior view

Answer 27

II, III, AVF

Question 28

Which lead is not used ?

Answer 28

AVR