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2. Electrophysiologic Properties of Cardiac Cells
Terms in this set (22)
Ability of pacemaker cell to initiate an electrical impulse without being stimulated from another source
Heart's unique trait
it has pacemaker cells that can generate an electrical impulse without being stimulated by a nerve
requires normal concentrations of K+, Na+, and Ca++
known as irritability; ability of cardiac muscle cells to respond to an outside stimulus such as that from a chemical, mechanical, or electrical source.
Ability of a cardiac cell to receive an electrical stimulus and conduct that impulse to an adjacent cardiac cell
Factors of conduction speed
can be altered by factors such as sympathetic and parasympathetic stimulation and medications
digitalis, dopamine, and epinephrine medications
the ability of myocardial cells to shorten in reponse to an impulse
Electrochemical potential change that occurs in the cell membrane that is necessary to initiate myocardial contraction
separated electrical charges of opposite polarity have potential energy, the measurement of this potential energy is called voltage
measured between two points in units of volts or millivolts
elements or compounds that break into charged particles when melted or dissolved in water or another solvent
Body fluids that contain electrolytes conduct and electric current
Depolarization. Contraction. Begins when cell receives an impulse. Na+ moves into cell rapidly, K+ leaves call, Ca moves slowly into cell. Responsible for QRS on ECG.
Early repolarization. Na+ channels partially close. Outward movement of K+. Fewer positive electrical charges within the cell.
Plateau Phase. Slow inward movement of Ca++ and slow outward movement of K+
Final Rapid Repolarization. K+ flows quickly out of the cell. Entry of Ca++ and Na+ stops. Corresponds with a T wave on the ECG.
Return to resting state. Heart is polarized. Cell will remain in this state until reactivated by another stimulus.
period of recovery which cells need after being discharged before they are able to respond to a stimulus.
Absolute Refractory Period
cells cannot be stimulated to conduct an electrical impulse, no matter how strong the stimulus. Onset of QRS complex to approximate peak of T wave.
Relative Refractory Period
cells can be stimulated to depolarize if the stimulus is strong enough. Known as the vulnerable period. Corresponds with down slope of T wave.
Weaker than normal stimulus can cause cardiac cells to depolarize. Corresponds with end of T wave. Dsyrhythmias can develop during this period.
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