Clin Lab - Cardiac Phys + Electrical fields & vectors Flashcards
What helps maintain a membrane potential at rest?
Na+/K+ pumps
Describe Na+ & K+ in relation to inside vs outside the cell
more Na+ outside the cell
more K+ inside the cell
Describe how the Na+/K+ pump pumps ions?
3 Na+ outside the cell
2 K+ inside the cell
What causes depolarization of cardiac muscle?
opening of Na+ channels
What allows for sustained contraction (the plateau)?
opening of K+ channels
Where is the refractory period?
this is where we reset everything. Na+/K+ pump works to move N+ back out and K+ back in
nothing can be done during this time.
What is the primary pacemaker of the heart? & why?
SA node, b/c it spontaneously depolarizes the fastest
EKG machine only picks up activity that is occurring….
outside of the cell
If the overall vector points towards a (+) electrode, there is ____ deflection of the EKG lead tracing
upward
If the overall vector points away from a (+) electrode, there is ____ deflection of the EKG lead tracing
downward
If the overall vector is perpendicular to the (+) electrode, there is ____ deflection of the EKG lead tracing
biphasic
Overall placement of the 10 electrodes
- one on each limb
- six on the chest wall
What does the R leg lead do?
serves a a ground - detects background signal that is subtracted out from other leads
List all the different standards EKG leads
I-III
aVR
aVL
aVF
V1-V6
Limb leads I-III are also known as…
bipolar leads
Describe Lead I
left arm (+), right arm (-)
views top of heart
Describe Lead II
left leg (+), right arm (-)
physiologic way the heart sits in the chest)
Describe Lead III
left leg (+), left arm negative
List the augmented leads
aVR - right arm (+)
aVL - left arm (+)
aVF - left food (+)
What leads give us the electrical activity in the frontal plane of heart?
Leads I, II, III, aVR, AVL, aVF
Where does the vector for Lead I point?
horizontally across the top of the heart
Where does the vector for Lead II point?
upwards at the heart from the left hip
Where does the vector for Lead III point?
upwards at the heart from the right hip
Where does the vector for Lead I point?
looking down at the heart from the left shoulder
Where does the vector for aVF point?
straight up at the heart from the feet
Where does the vector for aVR point?
looking down at the heart from the right shoulder
What are the precordial (chest) leads?
V1-V6
What do the chest leads show us?
horizontal plane of the heart
Placement of V1/V2
overlays the RV
V1 - right side of the sternum
V2 - left side of the sternum
Placement of V3/V4
overlays the septum
V4 - midclavicular line (5th intercostal space)
Placement of V5/V6
overlays the LV
angle around was we get to the left armpit area.
V1 & V2 are looking at…
RV
V3 & V4 are looking at the
septum
V5 & V6 are looking at the….
LV
