Commonly Used Terms - Cardiac Flashcards
The neurotransmitter released from the parasympathetic nervous system.
ACh
A decrease in potassium permeability that occurs when the electrical or chemical driving force on potassium is increased; inherent property of the cardiac cell membrane.
Anomalous (inward) rectification
Disturbance in the normal electrical activity of the heart due to either abnormal impulse formation, impulse conduction, or both.
Arrhythmia (dysrhtmia)
An intrinsic property of specialized cardiac cells to initiate their own electrical activity, i.e., pacemaker activity
Automaticity
Heart rate of <60 beats/minute
Bradycardia
Something that affects the pacemaker rate (frequency)
Chronotropic
The spread of electrical activity from cell to cell in the heart
Conduction
The speed with which conduction occurs; note that it is inversely related to conduction time
Conduction velocity
A transient depolarization of the membrane following an AP; an abnromal form of electrical activity caused by abnormally high intracellular calcium
Delayed afterdepolarization (DAD)
When the membrane potential becomes more positive than the resting membrane potential
Depolarization
A slow depolarization of the membrane potential that is responsible for the automaticity of cardiac pacemaker cells
Diastolic depolarization (phase 4)
Any cardiotonic steroid of glycoside that increases the contractile force of the myocardium (heart)
Digitalis
A transient depolarization of the membrane during the later portion of the plateau phase or phase 3 repolarization of an action potential; abnormal electrical events that may underlie some types of prolonged Q-T syndrome and other dysrhythmias.
Early afterdepolarization (EAD)
The period of time during an action potential when a stimulus (regardless of strength) cannot produce a regenerative action potential.
Effective refractory period (absolute refractory period)
The electrical potential and concentration gradient acting on an ion to cross the membrane; these two factors influence the movement of ions across the membrane (ionic current flow).
Electrochemical force
A theoretical value at which the concentration gradient and the electrical gradient acting on a single ion are balanced (calculated by the Nernst equation)
Equilibrium potential
When the membrane potential becomes more negative than the resting membrane potential
Hyperpolarization
Something that affects the contractility of muscular tissue
Inotropic
Visualized as pores within the sarcolemma through which ions move into and out of a cell
Ion channels
The flow of ions across the sarcolemmal membrane via ion channels; positive ions flowing into the cell represent inward current and positive ions flowing out of the cell represent outward current
Ionic current
Reduced blood flow to a region of tissue or an entire organ, usually as a result of an obstruction, such as a narrowed artery (not synonymous with hypoxia - lack of oxygen)
Ischemia
NT released from the sympathetic nervous system
NE
When a pacemaker cell is electrically stimulated at a rate faster than its own intrinsic rate, stopping the stimulation results in a temporary suppression of pacemaker activity
Overdrive suppression
The rate of voltage change during the action potential upstroke (NOT SPONTANEOUS RATE)
Rate of rise (dV/dt)
An abnormal form of conduction in which an impulse will re-excite previously excited tissue, resulting in sustained repetitive activity
Re-entry of excitation
The period of time during an AP when a stimulus can produce some type of regenerative AP
Relative refractory period
When the membrane potential returns to more negative levels following a depolarization
Repolarization
The electrical potential difference across a cell membrane; the inside being negative with respect to the outside positive
Resting membrane potential
The plasma membrane of a muscle cell
Sarcolemma
A protein within the sarcolemma which functions to remove sodium from the inside of the cell and to restore potassium to the inside of the cell; the movements are coupled and ATP is required.
Sodium-potassium pump
A protein in the sarcolemma which extrudes intracellular calcium from the cell in exchange for extracellular sodium flowing down its concentration gradient into the cell; does not depend directly on metabolic energy
Sodium-calcium exchange
The frequency (beats/minute) of pacemaker activity (NOT RATE OF RISE OR CONDUCTION VELOCITY)
Spontaneous rate
Heart rate greater than 100 beats/minute
Tachycardia
The membrane potential at which a regenerative action potential is produced; the value depends on the type of AP (slow vs. fast) as well as the ionic environment or presence of drugs
Threshold
Abnormal form of pacemaker activity usually lasting a short time, resulting from DADs or EADs
Triggered activity
