Ekg Chap 2 Flashcards
Two groups of cardiac cells
Myocardial cells
pacemaker cells
Myocardial cells
“working cells”
Found in the thin muscular layer of the atrial wall, and thicker muscular layer of the ventricular wall
What do myocardial cells contain
Myofibrils: contractible protein filament called actin and myosin
gives the indicator to contract and relax
Pacemaker cells
found in the electrical conductivity of the heart
responsible for the spontaneous generation of electrical impulses
Automaticity
Function - electrical
Pacemaker cells of the electrical conduction system
Excitability
Function - electrical
responding to an electrical stimulus
All cardiac cells
Conductivity
Function - electrical
conduct an electrical impulse to adjacent cardiac cell
All cardiac cells
Contractility
Function - Mechanical
cardiac cells to contract in response of an electrical stimulus
Myocardial cells
What happens during P-wave
SA node fires, causing atrial DEPOLARIZATION (atrium contracts)
Na+ enters, potassium gets out
negative to positive
resting to depolarized
What happens during P-Q
Signal travels to AV node, which fires after blood leaves the atria completely
atria DEPOLARIZATION complete
Na+ is already inside
Positive
What happens during QRS
Signal travels down Bundle of His and to the bundle branches
Purkinje fibers, causing ventricles to contract
Atra relaxing too
Ventricular depolarization begins
Na+ going out, potassium going in
Positive to negative
Ventricular What happens to S-T
Ventricular depolarization complete
Positive to negative
What happens to T wave
Ventricular repolarization begins
Isoelectric line (flat line)
Ventricular repolarization is complete
Negative
SA node
right upper atrium
60-100 beats/min
Pacemaker of heart
Interatrial tract (bachmann/s bundle)
conducts impulse from SA node to left atrium
Internodal tracts
three conduction tracts which conduct impulse from SA node through right atrium to AV node
AV node
serves as backup pacemaker firing 40-60 beats/min
slows conduction of electrical impulse through AV node to allow time for atrial contraction, delay in AV node (flat line in PR)
Bundle of His
Connects AV node to bundle branches
Bundle branches
Right/left branch which conducts electrical impulses to the right/left ventricle
Purkinje fibers
end of bundle branches, conducts electrical impulses to the ventricular myocardium
are capable of serving as backup pacemaker 30-40 beats/min or less
P-wave represents which chamber of heart
Atria
QRS wave represents which chambers of heart
ventricles
ECG graph paper
Horizontal line measures
Time
each small square horizontally measures 0.04seconds
ECG graph paper
Vertical line measures
Height/ amplitude/ voltage
1mm height
How to count beats per minute on graph paper
Each “R” multiplied by 10, is a beat per minute
