EKG- Chapter 1 Flashcards
While in the resting state, myocyets are polarized, the interior of every cell being _____ charged
negatively
The interiors of resting myocytes are negative, but when these cells are depolarized, their interiors become _________ and the cells contract.
positive
Depolarization may be considered an advancing wave of _____ charges within the heart’s myocytes.
positive
What initiates contraction of the resting myocytes as the charge within each cell changes to positive?
depolarization
What carries the cell to cell conduction of depolarizations through the myocardium?
fast moving Na+ions
During what phase do the myocyte interiors regain their resting negative charge?
repolarization
When does repolarization begin?
Immediately after depolarization
What causes myocardial contraction?
depolarization
What is the name of the recovery phase that follows depolarization?
repolarization
What two things of the myocardium are electrical phenomena caused by the movement of ions?
depolarization and repolarization
What are the skin sensors called that allow the EKG to record the electrical activity of the heart?
electrodes
When a positive wave of depolarization within the myocytes flows toward a positive electrode, what type of deflection occurs on the EKG?
upward deflection
What is the heart’s dominant pacemaker?
SA Node
What does the SA Node do?
It initiates a wave of depolarization that spreads outward, stimulating the atria to contract as the circular wave advances.
What is the pacing activity of the SA Node known as?
Sinus Rhythm
What is the generation of pace-making stimuli called?
automaticity
What are the focal areas of the heart called that have automaticity called?
automaticity foci
Where is the SA Node located?
upper posterior wall of the Right Atrium
Each depolarization wave of + charges proceeds outward from the SA Node and stimulate both atria to _______.
contract
Each depolarization wave emitted by the SA Node spreads through both atria and produce what on the EKG?
a P wave
What does the P wave on the EKG represent?
depolarization of both atria and the simultaneous contraction of the atria
What do the AV valves prevent?
They prevent ventricle to atrium blood backflow
What is another function of the AV valves?
They electrically insulate the ventricles from the atria
What part of the ventricles is not insulted from the atria by the AV valves?
The AV Node
What is the function of the AV Node?
It is the sole pathway to conduct the depolarization stimulus through the fibrous AV valves to the ventricles
What does conduction slow through the AV Node?
To allow time for the blood in the atria to enter the ventricles
What carries the slow conduction through the AV node?
Ca++ ions
Where does depolarization continue through after the AV Node?
Bundle of His
Where does depolarization continue after the Bundle of His?
Left and Right Bundle branches
Is conduction through the Bundle of His fast or slow?
fast
What types of fibers make up the Bundle of His and the Bundle Branches?
Purkinje fibers
Where do the terminal filaments of the Purkinje fibers rapidly distribute depolarization?
the ventricular myocytes
What does the depolarization of the ventricular myocardium record as on an EKG?
QRS
What is the entire ventricular conduction system composed of?
Purkinje fibers
What type of ions do the Purkinje fibers use for conduction?
Na+ ions
The Q wave always occurs at the beginning of the ________.
QRS complex
What type of deflection is the Q wave?
downward
What follows the Q wave?
R wave
Which way is the R wave deflected?
upward
Any downward wave preceded by an upward wave is an _____.
S wave
What does the QRS complex represent?
ventricular depolarization
What is the horizontal segment of the baseline that follows the QRS complex called?
ST segment
After the QRS, there is a segment of horizontal baseline followed by a broad hump called the __________.
T wave
What does the ST segment normally look like?
horizontal and flat, and level with other areas of the baseline
If the ST segment is elevated, what is this a sign of?
serious pathology ex: MI
What does the ST segment represent?
the “plateau” (initial) phase of ventricular repolarization
Why does repolarization occur?
So that the ventricular myocytes can recover their interior, resting negative charge, so they can be depolarized again
What does the T wave represent?
The rapid phase of ventricular repolarization
When does repolarization of the ventricular myocytes begin?
Immediately after the QRS and persists until the end of the T wave
Both phases of repolarization is accomplished by ____ ions leaving the myocytes
K+
When does ventricular systole begin?
with the QRS
Ventricular systole persists until the end of _________
the T wave.
What does ventricular contraction (systole) span?
depolarization and repolarization of the ventricles
What is the QT interval a representation of?
the duration of ventricular systole
How is the QT interval measured?
from the beginning of the QRS until the end of the T wave
What is the QT interval a good indicator of?
repolarization
What are patients with long QT intervals prone to?
rapid ventricular rhythms
When is the QT interval considered normal?
when it is less that half of the R to R interval at normal rates
What represents the cardiac cycle?
P wave, the QRS complex, the T wave and the baseline that follows until another P wave appears
