Pgs 1-9 Flashcards
What is the fastest part of the electrical circuit and the “rate controller” termed the pacemaker?
Sinoatrial node (SA node)
What is the SA node influenced by?
Autonomic tone (sympathetic increases rate and parasympathetic decreases rate)
What is the order of electrical discharge for each cardiac cycle?
SA–>AV–>Bundle of His–>left/right bundle branches–>anterior & posterior fascicles–>Purkinje fibers
Where is the SA node located?
Right atrium
What electrical activity creates the formation of the p wave?
Atria depolarization initiated by the SA node
Why is the p wave generally smaller than the QRS wave?
Muscle mass of the atria is fairly small and thus electrical changes are also small
Why is the speed with which the electrical depolarization travels through the AV node deliberately slow?
So that ventricular contraction will be correctly coordinated following atrial contraction.
What is the first part of the ventricles to depolarize?
The ventricular septum.
What does the Q wave represent?
When the ventricular septum depolarizes with a small wave that travels away from the positive electrode. This creates a small, downward deflection on the ECG paper.
What does the R wave represent?
When the bulk of the ventricular myocardium is depolarized.
What does the S wave represent?
After depolarization of the majority of the ventricles, the only remaining parts are the basilar portions of the ventricles. When this is depolarized, a small wave that travels away form the positive electrode, creating a small negative deflection on the ECG paper.
True or False: a Q wave always precedes an R wave
True
True or False: an R wave must be preceded by a Q wave.
False - an R wave may or may not be preceded by a Q wave. However, if there is a Q wave, it always precedes an R wave.
True or False: any downward deflection after an R wave is an S wave, regardless of the presence of a Q wave.
True
What does the T wave represent?
After complete depolarization and contraction of the ventricles, they repolarize for the next stimulus. This results in a deflection from the baseline, termed the T wave.
