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Heart and ECG.

441 Exam 1

Cardiac excitation normally begins with ... the SA node
what does the SA node do? repeatedly depolarize to threshold spontaneously- pacemaker potential
By conducting along the atrial muscle fibers, the action potential reaches the AV node
after the AV node the action potential reaches the... AV bundle
the bundle is the only site where action potentials can.. conduct from the atria to ventricles
after the AV bundle, the AP enters the... R and L bundle branches
the bundle branches extend through the... interventricular septum towards the apex
purkine fibers rapidly conduct the AP beginning at the apex of the heart upward to remainder of ventricular myocardium
an electrocardiogram (ECG or EKG) EKG-from German word is a recording of the electrical signals of the heart; a composite record of action potentials produced by all of the heart muscle fibers during each heart beat
electrocardiograph is the instrument used to record the changes
what can an ECG determine? if the conducting pathways is abnormal, if the heart is enlarged, if certain regions of the heart are damaged, and the cause of chest pain
The P wave represnets atrial depolarization
Atrial depolarization spreads from the ________ through the _________ SA node; contractile fibers in the atria
The QRS complex represents the onset of ___________ rapid ventricular depolarization
The T wave indicates _________ ventricular repolarization; occurs just as ventricles are starting the relax
The T wave is __________ and ___________ than the QRS complex. Why? smaller and wider because repolarization occurs more slowly than depolarization
Reading an ECG, the _________ of the waves can provide clues to abnormalities size
Larger P waves indicate… enlargement of the atria
An enlarged Q wave may indicate a … myocardial infarction
An enlarged R wave generally indicates… enlarged ventricles
The T wave is flatter than normal when.. the heart is receiving insufficient oxygen; ex) CAD
The T wave may be elevated in… hyperkalemia (high blood K+ level)
Analysis of an ECG involves measuring… the time spans between waves
Time span between waves intervals or segments
The P-Q interval is from the.. beginning of the P wave to the beginning of the QRS complex
What does the P-Q interval represent? conduction time from the beginning of atrial excitation to the beginning of ventricular excitation
Another way to look at it.. the P-Q interval is the time.. required for the action potential to travel through the atria, AV node, and remaining fibers of the conduction system.
What happens to the P-Q interval in disorders such as CAD and rheumatic fever? it lengthens
The S-T segment begins at the end of the S wave and ends at the beginning of the T wave
S-T segment represents time when the ventricular contractile fibers are depolarized during the plateau phase of the action potential
The S-T segment is elevated above the baseline in.. acute myocardial infarction
The S-T segment is depressed below the baseline in.. the heart receives insufficient oxygen
The Q-T interval goes from …. the start of the QRS complex to the end of the T wave
Q-T interval is the time … from the beginning of the ventricular depolarization to the end of ventricular repolarization
The Q-T interval may be lengthened by…. myocardial damage, myocardial ischemia, or conduction abnormalities
Myocardial ischemia decreased blood flow
Systole contraction
Diastole relaxation
The ECG waves predict… the timing of atrial and ventricular systole and diastole
ECG graph paper is divided into… 1 mm sections
Horizontal spacing .04 sec at 25 mm/sec
Bold lines .04 x 5
Vertical lines 10 mvolts
10 mm 100 mvolts
upward deflections positive
downward deflection negative
Normal P wave time .11 sec long, 2-3 mm tall
PR normal interval time .12-.20 sec
QRS normal interval time .05-.10 sec
Q wave norm time .04 sec, ¼ -1/3 height of R wave
What is S wave? ventricular depolarization away from electrode
QT seg norm time .4 to .44 sec
What is J point? where ST takes off from Q
A longer QRS complex time may mean ________ conduction block
Each little horizontal box ( 1 mm ) is the equivalent of how many seconds when the ECG is running at 25 mm/ sec? .04 sec
A normal PR interval time is… .12 to .20
A set of limb leads is…. aVL, ll, and lll
For normocardia, the HR must be… 60-100bpm
Created by: sbush0804



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