Chapter 1: Basic Principles Flashcards
Which scientist and in what year made a dead frog’s legs dance by electrical stimulation for the first time?
Luigi Galvani, 1790 (p. 1)
Which scientists and in what year discovered that the beating of the heart is due to a rhythmic discharge of electrical stimuli?
Kollicker and Mueller, 1855 (p. 2)
How did Kollicker and Mueller make this discovery?
They laid a motor nerve to a frog’s leg over its isolated beating heart, and saw that the leg kicked with each heartbeat. (p. 2)
Who invented the ECG as we know it?
Dr. Willem Einthoven
p. 4
What did Dr. Einthoven call his invention?
the ElectroKardioGram (EKG) which is the German spelling (p. 5)
The EKG records the…
…electrical activity of contraction of the myocardium.
p. 7
The interiors of ________ are ________ (“_________”) at rest, but when “depolarized” their interiors become ________ and the myocytes ________.
myocytes
negative ("polarized")
positive
contract
(p. 8)Depolarization may be considered an advancing ____ of ________ charges within the heart’s myocytes.
wave
positive
(p. 9)
The cell-to-cell conduction of depolarization through the myocardium in initiated by fast moving ______ ions.
sodium
p. 9
The myocyte interiors regain their _______ ________ ______ during the ______________ phase.
resting negative charge
repolarization
(p. 10)
In reality, repolarization begins ___________ _____ depolarization, but the “initial” repolarization does not ______ __ ___.
immediately after
record on EKG
(p. 10)
Sensors called __________ are placed on the skin to detect the heart’s electrical activity.
electrodes
p. 11
As the ________ wave of depolarization within the myocytes flows toward a positive electrode, there is a ________ (______) deflection recorded on EKG.
positive
positive (upward)
(p. 12)
The generation of pacemaking stimuli is known as…
…automaticity.
p. 13
Other focal areas of the heart that have automaticity are called “____________ ____”.
“automaticity foci”
p. 13
Atrial depolarization (and ___________) is a spreading ____ of ________ charges within the atrial myocardial cells.
contraction
wave
positive
Each depolarization wave emitted by the SA node spreads through ____ _____, producing a _ ____ on EKG.
both atria
P wave
(p. 14)
In reality, the contraction of the atria _____ ______ than the duration of the _ ____.
lasts longer
P wave.
(p. 15)
The atrioventricular valves do two major things:
- prevent backflow to the atria
- electrically insulate the ventricles from the atria
(p. 16)
The __ ____ is the ____ conducting path between the atria and the ventricles.
AV node
only
(p. 16)
Why does the wave of depolarization slow down when it enters the AV node?
To allow time for the blood in the atria to enter the ventricles.
(p. 19)
What portion of the EKG represents the pause as depolarization slows at the AV node?
The isoelectric line following the P wave.
p. 19
What ions are responsible for slowing conduction at the AV node?
calcium ions
p. 19
After conducting slowly through the AV node, depolarization _______ ______ through the ______ of ___ and the ____ and _____ ______ ________.
rapidly shoots
Bundle of His
left and right Bundle branches
(p. 20)
The ventricular conduction originates at the ______ __ ___, which penetrates the AV valves, then immediately __________ (in the ________________ ______) into the left and right bundle branches.
Bundle of His
bifurcates
interventricular septum
(p. 20)
The bundle of His, and bundle branches are “bundles” of…
…rapidly conducting Purkinje fibers.
p. 20
Purkinje fibers use ____-______ ______ ions for the conduction of depolarization.
fast-moving sodium
p. 20
The terminal filaments of the Purkinje fibers rapidly distribute depolarization to the…
…ventricular myocytes.
p. 21
The rapid passage of depolarization down the ventricular conducting system is too ____ to record on EKG; however, depolarization of the ventricular myocardium records as a ___ ______.
weak
QRS complex
(p. 21)
The terminal filaments of the Purkinje fibers spread out just beneath the ___________ that _____ both ventricular cavities, therefore ventricular depolarization begins at the ______ and proceeds toward the outside surface (__________).
endocardium, lines
lining, epicardium
(p. 21)
The Purkinje fibers ______ and _________ just beneath the endocardial lining, but they barely _________ into the myocardium.
branch, subdivide, penetrate
p. 21
The entire ventricular conduction system, i. e. the…
… is composed of…
…bundle of His through the terminal filaments…
…Purkinje fibers that use fast-moving Na+ ions for conduction.
p. 22
The Q wave, which is not always _______, is the first ________ deflection of the complex.
present
downward
(p. 23)
By convention, if there is any UPWARD deflection in a QRS complex that appears before a Q wave…
…it is not a Q wave, because the Q wave is always the first wave in the complex.
(p. 23)
The upward _ ____ is followed by a downward _ ____.
R wave
S wave
(p. 24)
An upward wave is ALWAYS called…
…an R wave.
p. 24
What do we call a complex with a downward wave and no upward waves?
A QS wave; when there is no upward wave, we cannot determine whether it is a Q wave or an S wave, so it is called a QS wave. BUT, it is considered to be a Q wave when we look for Q’s.
(p. 25)
The T wave represents the…
…rapid phase of ventricular repolarization.
p. 27
Repolarization is accomplished by…
…potassium (K+) ions leaving the myocytes.
p. 27
Why is the QT interval a good indicator of repolarization?
Because repolarization comprises most of the QT interval.
p. 28
As a simple rule of thumb, the QT interval is considered normal when it is…
…less than half of the R-to-R interval at normal rates.
p. 28
Following depolarization, repolarization is due to the controlled _______ of __ ions from the myocytes.
outflow
K+
(p. 30)
Cell-to-cell conduction (of depolarization) through the __________ is carried by ___ ____, however, __ ____ conduction is due to the ____ movement of ___ ions.
myocardium, Na+ ions,
AV node, slow, Ca++
(p. 30)
Lead I is created by placing a positive electrode on…
…and the negative electrode on the…
…the left arm
…right arm.
(YouTube https://www.youtube.com/watch?v=URBREKIUALk)
Lead II is created by placing a positive electrode on…
…and the negative electrode on the…
…the left foot
…right arm.
Lead III is created by placing a positive electrode on…
…and the negative electrode on the…
…the left foot.
…left arm.
Phase 0 of the cardiac cycle of contraction begins with rapid depolarization due to…
…opening of voltage-gated fast sodium channels.
Powerpoint by Dr. Miller; “Basic EKG, Fall 2016”
Phase 1 is reached when the membrane potential is at its most ________ state.
positive
Powerpoint by Dr. Miller; “Basic EKG, Fall 2016”
The phase 2 plateau is due to opening of…
…voltage-gated slow calcium channels and closing of some of the potassium channels.
(Powerpoint by Dr. Miller; “Basic EKG, Fall 2016”)
Phase 3 is repolarization, which is due to…
…opening of voltage-gated K channels and closing of calcium channels.
(Powerpoint by Dr. Miller; “Basic EKG, Fall 2016”)
Events in the Cardiac Cycle: Phase 1: Phase 2: Phase 3: Phase 4: Phase 5: Phase 6: Phase 7:
1 - atrial systole, then mitral/tricuspid valves close producing S1
2 - isovolumetric contraction, then aortic/pulmonic valves open
3 - rapid ejection
4 - reduced ejection, then aortic/pulmonic valves close
5 - isovolumetric relaxation, then mitral/tricuspid valves open
6 - rapid filling
7 - reduced filling
