ICU EXAM 3 (ALL THINGS CARDIAC) 136
QUESTIONS WITH COMPLETE SOLUTIONS!!
what is the purpose of the SA node? Answer - initiates the electrical activity of
the heart, sets the HR (rate: 60-100 bpm)
what do the internodal fibers do in the heart? Answer - transmit the impulse
from the SA node to the AV node via right atrium muscle
what does the AV node do? Answer - delays the ventricular impulse until the
ventricles fill, rate 40-60 bpm
what does the Bundle of His do? Answer - transmits the impulse to the Bundle
Branch system
what to the Purkinje fibers do? Answer - conducts impulses into
subendocardial layers, depolarizes from endocardium to epicardium
what 6 things does an ECG/EKG tell you? Answer - size of the heart
orientation of the heart (NOT on a rhythm strip!)
rhythm disturbances
ischemia, injury, or infarct (if present)
electrolyte abnormalities
drug toxicity
P wave represents what? Answer - atrial depolarization
,QRS complex represents what? Answer - ventricular depolarization
Q wave reflects what? Answer - the initial negative deflection from baseline
(there's only a Q wave if the first deflection is negative)
R wave is what? Answer - the first positive deflection from baseline
S wave refers to what? Answer - the subsequent negative deflection after the R
wave
T wave represents what? Answer - repolarization of the ventricle
U wave represents what? Answer - repolarization of the Purkinje fibers (not
often present on an EKG)
when does atrial repolarization occur? Answer - during QRS (which is
ventricular depolarization
PR interval represents what? Answer - the time it takes for the electrical
impulse to move from the SA to AV node
how long is the PR interval? Answer - 0.12 to 0.20 seconds (3-5 boxes)
QRS width is usually how many seconds? Answer - = or < 0.10 sec (2.5 boxes)
what does a wide QRS complex reflect? Answer - poor conduction in the
Bundle of His (takes longer to conduct the impulse)
, what is the QTc interval? Answer - measured from the beginning of the QRS
complex to the end of the T wave
can show drug issues
is also corrected for HR
T/F: the EKG strip does not imply contraction, only electrical activity Answer -
True, you have to check for a pulse because the heart may not be beating even
if the electrical activity is sending impulses to beat
what is membrane potential in heart cells? Answer - a difference in electrical
charge across a semi-permeable membrane
what is automaticity? Answer - the ability to spontaneously depolarize
what is rhythmicity? Answer - the ability to depolarize regularly
what is refractoriness? Answer - the state of a cell during repolarization when
cells either:
cannot depolarize regardless of stimulus intensity
require a much greater stimulus than normal
during resting membrane potential, where is Na+ concentration greater, inside
or outside the cell? Answer - Na+ concentration is greater outside the cell
during resting membrane potential, where is K+ concentration greater, inside
or outside the cell? Answer - K+ concentration is greater inside the cell
QUESTIONS WITH COMPLETE SOLUTIONS!!
what is the purpose of the SA node? Answer - initiates the electrical activity of
the heart, sets the HR (rate: 60-100 bpm)
what do the internodal fibers do in the heart? Answer - transmit the impulse
from the SA node to the AV node via right atrium muscle
what does the AV node do? Answer - delays the ventricular impulse until the
ventricles fill, rate 40-60 bpm
what does the Bundle of His do? Answer - transmits the impulse to the Bundle
Branch system
what to the Purkinje fibers do? Answer - conducts impulses into
subendocardial layers, depolarizes from endocardium to epicardium
what 6 things does an ECG/EKG tell you? Answer - size of the heart
orientation of the heart (NOT on a rhythm strip!)
rhythm disturbances
ischemia, injury, or infarct (if present)
electrolyte abnormalities
drug toxicity
P wave represents what? Answer - atrial depolarization
,QRS complex represents what? Answer - ventricular depolarization
Q wave reflects what? Answer - the initial negative deflection from baseline
(there's only a Q wave if the first deflection is negative)
R wave is what? Answer - the first positive deflection from baseline
S wave refers to what? Answer - the subsequent negative deflection after the R
wave
T wave represents what? Answer - repolarization of the ventricle
U wave represents what? Answer - repolarization of the Purkinje fibers (not
often present on an EKG)
when does atrial repolarization occur? Answer - during QRS (which is
ventricular depolarization
PR interval represents what? Answer - the time it takes for the electrical
impulse to move from the SA to AV node
how long is the PR interval? Answer - 0.12 to 0.20 seconds (3-5 boxes)
QRS width is usually how many seconds? Answer - = or < 0.10 sec (2.5 boxes)
what does a wide QRS complex reflect? Answer - poor conduction in the
Bundle of His (takes longer to conduct the impulse)
, what is the QTc interval? Answer - measured from the beginning of the QRS
complex to the end of the T wave
can show drug issues
is also corrected for HR
T/F: the EKG strip does not imply contraction, only electrical activity Answer -
True, you have to check for a pulse because the heart may not be beating even
if the electrical activity is sending impulses to beat
what is membrane potential in heart cells? Answer - a difference in electrical
charge across a semi-permeable membrane
what is automaticity? Answer - the ability to spontaneously depolarize
what is rhythmicity? Answer - the ability to depolarize regularly
what is refractoriness? Answer - the state of a cell during repolarization when
cells either:
cannot depolarize regardless of stimulus intensity
require a much greater stimulus than normal
during resting membrane potential, where is Na+ concentration greater, inside
or outside the cell? Answer - Na+ concentration is greater outside the cell
during resting membrane potential, where is K+ concentration greater, inside
or outside the cell? Answer - K+ concentration is greater inside the cell
