EMT 254 Flashcards
(38 cards)
Automaticity
pacemaker cells can create their own electrical impulses
Excitability
ability of cardiac cells to respond to an electrical stimulus
Conductivity
ability for cardiac cells to receive an electrical stimulus and transmit it to other cardiac cells
Contractility
ability for cardiac cells to shorten and cause cardiac contraction
Myocardial cells are responsible for:
generating the physical contraction of the heart muscle
Pacemaker cells are responsible for:
controlling the rate and rhythm of the heart
Pacemaker cells have the ability to:
create their own electrical impulse without being stimulated
The three major cations that effect cardiac function:
Potassium (K), Sodium (Na) and Calcium (Ca)
Primary cations inside the cell:
Potassium, magnesium and calcium
A major cation outside the cell:
Sodium
At the resting state:
Potassium is greater inside the cell
Sodium is greater outside the cell
Cardiac depolarization it’s thought of as:
the period in which sodium ions rush into the cell
Sodium – potassium pump:
sodium returns outside of the cell and potassium returns inside the cell
The two stages of repolarization:
Absolutely refractory period (cell is unable to respond to a new electrical stimulus) from QRS - peak of T-wave
Relative refractory period (went repolarization is almost complete, the cell can be stimulated if the stimulus is stronger than normal), downward slope of the T-wave
5 step approach to reading ECG’s:
Herat rate, Heart rhythm, P-wave, PR Interval, QRS complex
PR Interval
0.12-0.20
QRS Interval
P-wave
Impulse spreads across the atria and triggers atrial contraction
QRS Complex
Impulse spreads across to ventricles, triggering ventricle contraction
T-wave
Ventricle returning to resting state
Which are bipolar leads
Leads I, II, III
V1 Placement
4th intercostal space, right of the sternum
V2 Placement
4th intercostal space, left of the sternum
V3 Placement
5th intercostal space, 1/2 way between V2 and V3
