Heart vocabulary (taken from handout on heart 5)

Question 1

Acetylcholine

Answer 1

Neurotransmitter released from the parasympathetic nervous system

Question 2

Anomalous (inward) rectification

Answer 2

Decrease in potassium permeability that occurs when the electrical or chemical driving force on potassium is increased, which is an inherent property of the cardiac cell membrane

Question 3

Arrhythmia (dysrhythmia)

Answer 3

A disturbance in the normal electrical activity of the heart due to either abnormal impulse formation, impulse conduction, or both.

Question 4

Automaticity

Answer 4

An intrinsic property of specialized cardiac cells to initiate their own electrical activity

Question 5

Bradycardia

Answer 5

heart rate of less than 60 beats/minute

Question 6

Chronotropic

Answer 6

Affecting the pacemaker rate

Question 7

Conduction

Answer 7

The spread of electrical activity from cell to cell in the heart

Question 8

Conduction velocity

Answer 8

The speed with which conduction occurs; expressed in meters/second. Conduction velocity is inversely related to the conduction time.

Question 9

Delayed afterdepolarization

Answer 9

A transient depolarization of the membrane following an action potential. DAD’s are an abnormal form of electrical activity caused by abnormally high intracellular calcium.

Question 10

Depolarization

Answer 10

When the membrane potential becomes more positive than the resting membrane potential

Question 11

Diastolic depolarization (phase 4)

Answer 11

A slow depolarization of the membrane potential that is responsible for the automaticity of cardiac pacemaker cells

Question 12

Digitalis

Answer 12

A general term that refers to any cardiotonic steroid or glycoside that increases the contractile force of the heart

Question 13

Early afterdepolarization

Answer 13

A transient depolarization of the membrane during the later portion of the plateau phase or phase 3 repolarization of an action potential. EAD’s are abnormal electrical events that may underlie some types of prolonged Q-T syndrome and other dysrhythmias

Question 14

Effective (absolute) refractory period

Answer 14

The period of time during an action potential when a stimulus, regardless of strength, cannot produce a regenerative action potential.

Question 15

Electrochemical force

Answer 15

The electrical potential and concentration gradient action on ion to cross the membrane; these two factors influence the movement of ions across the membrane

Question 16

Equilibrium potential

Answer 16

A theoretical value at which the concentration gradient and the electrical gradient acting on a single ion are balanced. This value is calculated by the Nernst equation

Question 17

Hyperpolarization

Answer 17

When the membrane potential becomes more negative than the resting membrane potential

Question 18

Inotropic

Answer 18

Affecting the contractility of muscular tissue

Question 19

Ion channels

Answer 19

Visualized as pores within the sarcolemma through which ions move into and out of a cell

Question 20

Ionic current

Answer 20

The flow of ions across the sacrolemmal membrane via ion channels; positive ions flowing into the cell represent inward current and positive ions flowing out of the cell represent outward current

Question 21

Ischemia

Answer 21

Reduced blood flow to a region of tissue or an entire organ, usually a result of obstruction, such as narrowed arteries. Not synonymous with a lack of oxygen (hypoxia).

Question 22

Norepinephrine

Answer 22

Neurotransmitter released from the sympathetic nervous system

Question 23

Overdrive suppression

Answer 23

When a pacemaker cell is electrically stimulated at a rate faster than its own intrinsic rate (overdrive), stopping the stimulation results in a temporary suppression of pacemaker activity

Question 24

Rate of rise (dV/dt)

Answer 24

Refers to the rate of voltage change during the action potential upstroke; expressed in volts/second. Do not confuse this term with spontaneous rate.

Question 25

Re-entry of excitation

Answer 25

An abnormal form of conduction in which an impulse will re-excite previously excited tissue, resulting in sustained repetitive activity

Question 26

Relative refractory period

Answer 26

The period of time during an action potential when a stimulus can produce some type of regenerative action potential

Question 27

Repolarization

Answer 27

When the membrane potential returns to more negative levels following a depolarization

Question 28

Resting membrane potential

Answer 28

The electrical potential difference across a cell membrane; the inside being negative with respect to the outside positive

Question 29

Sarcolemma

Answer 29

The plasma membrane of a muscle cell

Question 30

Sodium-potassium pump

Answer 30

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 movement of sodium and potassium are coupled and metabolic energy is required

Question 31

Sodium-calcium exchange

Answer 31

A protein in the sarcolemma which extrude intracellular calcium from the cell in exchange for extracellular sodium flowing down its concentration gradient into the cell. This process does not depend directly on metabolic energy

Question 32

Spontaneous rate

Answer 32

The frequency of pacemaker activity. Do not confuse this term with rate of rise or conduction velocity

Question 33

Tachycardia

Answer 33

Heart rate greater than 100 beats/minute

Question 34

Threshold

Answer 34

The membrane potential at which a regenerative action potential is produced. This value depends on the type of action potential as well as the ionic environment or presence of drugs

Question 35

Triggered activity

Answer 35

Abnormal form of pacemaker activity usually lasting a short time, resulting from DAD’s or EAD’s