Cardio Intro Flashcards
the fundamental electrical event of the heart
depolarization
cardiac cells restoring their resting polarity
repolarization
every wave on the ECG is the manifestation of _____ and _____
depolarization
repolarization
what is the electrical power source of the wave of depolarization?
pacemaker cells
the hard wiring of the heart that carries currents rapidly and efficiently to distant regions of the heart
electrical conducting cells
the largest part of the heart tissue that is responsible for the heavy labor of relaxing, contracting and pumping blood
myocardial cells
the pacemaker currents of which node bring cells to threshold more rapidly?
SA node
what is the inherent rate of the SA node?
100 depolarizations per minute
why do we want the SA node to reach threshold first?
we want it to drive the heartbeat forward
cardiac muscle wants to fire in an ordered and rhythmic fashion. what is this called?
myogenic
what is the condition in which cardiac muscle cells fire without a functioning SA node pacemaker and is chaotic and ineffective?
fibrillation
why can the heart still beat properly even if its connections to the CNS are completely severed?
because the SA node has automaticity
SA node is the first to _____ but the slowest to _____
depolarize
repolarize
during sympathetic, what ions are increased?
K+ and Ca+
what do norepi and epi during sympathetic affect?
atria and ventricles
during parasympathetic, what ion leaks out of the SA node?
K+
what does acetylcholie during parasympathetic affect?
atria
what deflection does a positive charge moving towards a positive electrode give?
upward/positive deflection
what deflection does a positive charge moving perpendicular to a positive electrode give?
no deflection
what deflection does a positive charge moving away a positive electrode give?
downward/negative deflection
electricity flows from _____ to _____
negative
positive
lead V1 should be mostly _____
negative
lead V6 should be mostly _____
positive
what will be seen on the ECG if the heartbeat is initiated in the SA node and the atria contract?
P wave
what is it called when the impulse slows as it passes through the AV node from the atria to the ventricles?
atrial kick
why is the atrial kick important?
allows atria time to finish filling the ventricles
what will be seen on the ECG during the rapid impulse through the His-Purkinje system?
PR interval
what generates the QRS complex on the ECG?
depolarization of septum and ventricular walls
what represents repolarization of the ventricles on the ECG?
ST segment and T wave
what does the horizontal axis of the ECG measure?
time
on the horizontal axis, how many seconds is one small box?
0.04 seconds
on the vertical axis, how many millivolts is 1 large box?
0.5 mv
what is the normal size of the P wave?
0.5 - 2.5 small boxes tall and wide
how long in seconds is a normal PR interval?
0.12 - 0.20 seconds
the first negative deflection following the PR segment is always known as what?
Q wave
the first positive deflection following Q wave or PR segment is always known as what?
R wave
the negative deflection that extends below baseline after the R wave is known as what?
S wave
how long is a narrow QRS complex?
less than 3 small boxes
what does a narrow QRS complex indicate?
signal came from above the AV node
what does a wide QRS complex indicate?
previous AMI
what does the ST segment represent?
refractory period
what does the T wave represent?
repolarization of the ventricles
what is the max amplitude of the T wave in the limb leads?
5mm (1 big box)
what is the max amplitude of the T wave in the chest leads?
10mm (2 big boxes)
what measure the time of ventricular depolarization and repolarization?
QT interval
what is the normal duration of the QT interval?
9-11 small boxes
what does the U wave represent?
repolarization of the purkinje fibers
what is the max amplitude of the U wave?
1 mm (1 small box)
