EKG basics Flashcards
what is true of myocytes
polarized at rest inside is negatively charged compared to out membrane pumps (control ion distribution) necessary to keep inside electronegative
what is needed to keep cell polarized (in this state)
ATP
Na K pump moves how many ions?
3 Na out
2 K in
how do cardiac cells lose their internal negativity?
depolarization
how many types of cells in the heart?
- pacemaker cells - power
- electrical conducting cells - wiring
- myocardial cells - contraction
what is true of pacemaker cells
innate electrical characteristics
input from nerual and hormonal
serve as a source of a wave of depolarization
what are the phases of action potential
phase 0 - rapid Na influx phase 1 - K & Cl efflux phase 2 - Ca influx K efflux phase 3 - K efflux phase 4 - K influx
what is automaticity?
all heart cells possess ability to behave as a pacemaker. Suppressed unless SA node fails
What is rate of of sites?
sa - 60-100 / min
av - 40 - 60
bundle 30 - 40
perk. 30 - 40
what is excitation- contraction coupling?
Actin and Myosin and when a wave of depolarization reaches a myocardial cell, calcium is released within the cell, causing the cell to contract.
True or false: Myocardial cells CAN transmit electrical current like conducting cells
true
what is time and length of small squares?
1 mm
0.04 s
what is time and length of big squares?
5 mm
0.2 s
verticle axis = voltage
small square - 0.1 mV
big square - 0.5 mV
what does PR interval represent?
start of atrial depolarization to start of ventricular depolarization.
What does ST segment represent?
Measures time from the end of ventricular depolarization to the start of ventricular repolarization
What does QT segment represent?
Measures time from beginning of ventricular depolarization to the end of ventricular repolarization.
how does a biphasic wave come about?
depolarizing wave moving perpendicular to a positve electrode
12 lead ECG consists of what types of leads?
6 limb (3 standard 3 augmented) 6 precordial
what are the signs on lead 1
right arm ( – ) left arm( +)
what are the signs on lead 2
right arm ( –) legs( +)
what are the signs on lead 3
left arm (–) legs( +)
what is true of precordial leads?
illustrate horizontal plane
all electrodes are (+) with (-) central terminal
what are positions for precordial electrodes?
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
