Test 1: lecture 3 +4 ekg intro Flashcards
change from — to — happens inside cell during action potential
negative to positive
— is the ability of certain cardiac cells to initiate an electrical signal
automaticity
why is HR controlled by SA node
automaticity of those cardiac cells produce a signal at a faster rate then any other cell types in the heart, blocks out other signals
if SA node disfunctional heart will beat according to AV node
— is the ability of cardiac cells to respond to an electrical signal
excitability
resting cell at -70
Na/K pump pushed 3 Na out and 2 K in. results in net negative
K will diffuse into or out of the cell
out of cell
will keep inside of cell negative
what happens during depolarization
rush of Na and Ca into a cell makes it positive inside
what happens during repolarization
cell returns to resting negative
potasium(K) diffuses out of cell
explain fast response action potential
cell negative at rest at -90 mV
stimulus causes rapid depolarization as Na floods into cell
Ca slowly comes into cell- 2 steady state-then stops
K leaks out of cell- causing repolarization
Na/K pump returns cell to normal resting
explain slow response AP
pacemaker cells
can cause impulse on its own
resting at -60mV
DOES NOT need outside actional potential
steady influx of Calcium causes AP
repolarization caused by K leaking back out
slow or fast response AP causes automaticity
slow
think SA or AV node
can trigger itself by slow influx of Ca into the cell
what part of the heart has a slow conduction velocity
SA and AV node
controlled by slow response AP- slow influx of Ca into the cell
allows for the atria to empty into the ventricles before the ventricles contract
what part of the heart has a fast conduction velocity
purkinje fibers
atrial muscle
ventricular muscle
controlled by fast response AP- rapid influx of Na into the cell
explain cardiac excitation-contraction coupling
when cardiac cell is depolarized (becomes more +)
calcium comes into cell, increased intracellular calicum leads to increased sarcomere activation= contraction of the muscle cell
fast EKG paper speed
50 mm/s
1 small square= 0.02 seconds
BIC: # R-R intervals x 20 for bpm
instantaneous: 3000/RR interval= bpm
slow EKG paper speed
25 mm/s
1 small square = 0.04 seconds
BIC: # R-R intervals x 10 for bpm
instantaneous: 1500/RR interval= bpm
a voltage change of 2 mV would be how many squares
20 mm (20 small squares)
20 squares tall
what color electrodes on what limb
black- left arm
red- left leg
white- right arm
green- right leg
lead 1 has + and - where
R arm negative
left arm positive
lead 2 has + and - where
positive left leg
negative right arm
lead 3 has + and - where
positive left leg
negative left arm
how to form augmented leads
aVR= will have positive on right arm and average negatives of L arm and L leg
aVR, aVL, aVF will look at heart from different prospectives on frontal plane (cranial to caudal and left to right)
where are the leads in a hexaxial mapping system
depolarizing current will cause an internal change from — to — and if moving toward the positive electrode will be seen at —
negative to positive
toward positive = positive deflection
away form electrode = negative deflection
