Ch 11 Vocab electro

Question 1

Anode

Answer 1

 ​The positive electrode.

Question 2

Cathode

Answer 2

 ​The negative electrode.

Question 3

Charge

Answer 3

 ​One of the basic properties of matter, which has no charge (is electrically neutral) or may be negatively (−) or positively (＋) charged. Charge is noted as Q and is measured in Coulombs (C). Charge is equal to current (I) × time (t). Q ＝ It

Question 4

Current density

Answer 4

 ​The amount of current per unit area.

Question 5

Electrical current

Answer 5

 ​The movement or flow of charged particles through a conductor in response to an applied electrical field. Current is noted as I and is measured in amperes (A).

Question 6

Electrical muscle stimulation (EMS)

Answer 6

 ​Application of an electrical current directly to muscle to produce a muscle contraction.

Question 7

Functional electrical stimulation (FES)

Answer 7

 ​Application of an electrical current to produce muscle contractions that are applied during a functional activity. Examples of FES include the electrical stimulation of dorsiflexion during the swing phase of gait and the stimulation of wrist and finger flexion during grasp activities.

Question 8

Gate control theory

Answer 8

 ​A theory of pain control and modulation stating that pain is modulated at the spinal cord level by inhibitory effects of nonnoxious afferent input.

Question 9

Impedance

Answer 9

 ​The total frequency-dependent opposition to current flow. Impedance is noted by Z and is measured in Ohms (Ω). For biological systems, impedance describes the ratio of voltage to current more accurately than resistance because it includes the effects of capacitance and resistance.

Question 10

Iontophoresis

Answer 10

 ​The delivery of ions through the skin for therapeutic purposes using an electrical current.

Question 11

Motor point

Answer 11

 ​The place in a muscle where electrical stimulation will produce the greatest contraction with the least amount of electricity, generally located over the middle of the muscle belly.

Question 12

Neuromuscular electrical stimulation (NMES)

Answer 12

 ​Application of an electrical current to motor nerves to produce contractions of the muscles they innervate.

Question 13

Ohm’s law

Answer 13

 ​A mathematical expression of how voltage, current, and resistance relate, where voltage equals current multiplied by resistance. V=IR

Question 14

Phase

Answer 14

 ​In pulsed current, the period from when current starts to flow in one direction to when it stops flowing or starts to flow in the other direction. A biphasic pulsed current is made up of two phases; the first phase begins when current starts to flow in one direction and ends when the current starts to flow in the other direction, which is also the beginning of the second phase. The second phase ends when current stops flowing.

Question 15

Polarity

Answer 15

 ​The charge of an electrode that will be positive (the anode) or negative (the cathode) with a direct or monophasic pulsed current and is constantly changing with an alternating or biphasic pulsed current.

Question 16

Pulse

Answer 16

 ​In pulsed current, the period when current is flowing in any direction.

Question 17

Resistance

Answer 17

 ​Opposition of a material to the flow of electrical current. Resistance is noted as R and is measured in Ohms (Ω).

Question 18

Voltage

Answer 18

 ​The force or pressure of electricity; the difference in electrical energy between two points that produces the electrical force capable of moving charged particles through a conductor between those two points. Voltage is noted as V and is measured in volts (V); also called potential difference.

Question 19

Alternating current (AC)

Answer 19

 A continuous bidirectional flow of charged particles (see Fig. 11-2). AC has equal ion flow in each direction, and thus no pulse charge remains in the tissues. Most commonly, AC is delivered as a sine wave. With AC, when the frequency increases, the cycle duration decreases, and when the frequency decreases, the cycle duration increases (Fig. 11-22).

Question 20

Biphasic pulsed current

Answer 20

 ​A series of pulses wherein the charged particles move in one direction and then in the opposite direction (see Fig. 11-6,B).

Question 21

Continuous current

Answer 21

 ​A continuous flow of charged particles without interruptions or breaks. A continuous current that goes in one direction only is known as a direct current (DC). A continuous current that goes back and forth in two directions is known as an alternating current (AC).

Question 22

Direct current (DC)

Answer 22

 ​A continuous unidirectional flow of charged particles (see Fig. 11-1).

Question 23

Interferential current

Answer 23

 ​Interferential current is the waveform produced by the interference of two medium-frequency (1000 to 10,000 Hz) sinusoidal ACs of slightly different frequencies. These two waveforms are delivered through two sets of electrodes through separate channels in the same stimulator. Electrodes are configured on the skin so that the two ACs intersect (see Fig. 11-3, A).

Question 24

Medium-frequency AC

Answer 24

 ​An AC with a frequency between 1000 and 10,000 Hz (between 1 and 10 kHz). Most medium-frequency currents available on clinical units have a frequency of 2500 to 5000 Hz. Medium-frequency AC is rarely used alone therapeutically, but two medium-frequency ACs of different frequency may be applied together to produce an interferential current (see Interferential current).

Question 25

Monophasic pulsed current

Answer 25

 ​A series of pulses wherein the charged particles move in only one direction (see Fig. 11-6,A).

Question 26

Premodulated current

Answer 26

 ​An alternating current that uses a medium-frequency sinusoidal waveform with sequentially increasing and decreasing current amplitude, and is produced with a single circuit using two electrodes. This current has the same waveform as an interferential current produced by the interference of two medium-frequency sinusoidal ACs requiring four electrodes (see Fig. 11-4).

Question 27

Pulsed current (pulsatile current)

Answer 27

 ​An interrupted flow of charged particles whereby the current flows in a series of pulses separated by periods when no current flows. The current may flow in one direction only or may flow back and forth during each pulse.

Question 28

Russian protocol

Answer 28

 ​A medium-frequency AC with a frequency of 2500 Hz delivered in 50 bursts/second. Each burst is 10 ms long and is separated from the next burst by a 10 ms interburst interval (see Fig. 11-5). This type of current is also known as medium-frequency burst AC (MFburstAC), and when this term is used, the frequency of the medium-frequency current or the bursts may be different from the original protocol.

Question 29

Frequency

Answer 29

 ​The number of cycles or pulses per second. Frequency is measured in Hertz (Hz) for cycles or pulses per second (pps) for pulses (see Fig. 11-11).

Question 30

Interphase interval (intrapulse interval)

Answer 30

 ​The time between phases of a pulse (Fig. 11-23).

Question 31

Interpulse interval

Answer 31

 ​The time between individual pulses (see Fig. 11-9).

Question 32

On/Off time

Answer 32

 ​On time is the time during which a train of pulses occurs. Off time is the time between trains of pulses when no current flows. On and off times are usually used when the goal of electrical stimulation is to produce muscle contractions. During on time, the muscle contracts, and during off time, it relaxes. Off time is required to reduce muscle fatigue during the stimulation session.

Question 33

Phase duration

Answer 33

 ​The duration of one phase of a pulse. Phase duration is generally expressed in microseconds (μs × 10−6 seconds) or milliseconds (ms × 10−3 second) (see Fig. 11-9).

Question 34

Pulse duration

Answer 34

 ​Time from the beginning of the first phase of a pulse to the end of the last phase of a pulse. Pulse duration is generally expressed in microseconds (μs × 10−6 seconds) (see Fig. 11-9).

Question 35

Ramp up/ramp down time

Answer 35

 ​The ramp up time is the time it takes for the current amplitude to increase from zero, at the end of the off time, to its maximum amplitude during the on time. A current ramps up by having the amplitude of the first few pulses of on time gradually be sequentially higher than the amplitude of the previous pulse. The ramp down time is the time it takes for the current amplitude to decrease from its maximum amplitude during on time back to zero (Fig. 11-13). Ramp up and ramp down times are different from rise and decay times. The latter describe the time needed for the current amplitude to increase and decrease during a phase.

Question 36

Rise time/decay time

Answer 36

 ​Rise time is the time it takes for the current to increase from zero to its peak during any one phase. Decay time is the time it takes for the current to decrease from its peak level to zero during any one phase (Fig. 11-24). Note that this is different from ramp up/ramp down time as described previously.

Question 37

Wavelength

Answer 37

 ​The duration of 1 cycle of AC. A cycle lasts from the time the current departs from the isoelectric line (zero current amplitude) in one direction and then crosses the isoelectric line in the opposite direction to when it returns to the isoelectric line. The wavelength of alternating current is similar to the pulse duration of pulsed current (Fig. 11-25).

Question 38

Amplitude (intensity)

Answer 38

 ​The magnitude of current or voltage (see Fig. 11-10).

Question 39

Amplitude modulation

Answer 39

 ​Variation in peak current amplitude over time.

Question 40

Burst mode

Answer 40

 ​A current composed of series of pulses delivered in groups known as bursts. The burst is generally delivered with a preset frequency and duration. Burst duration is the time from the beginning to the end of the burst. The time between bursts is called the interburst interval (Fig. 11-26).

Question 41

Frequency modulation

Answer 41

 ​Variation in the number of pulses or cycles per second delivered.

Question 42

Modulation

Answer 42

 ​Any pattern of variation in one or more of the stimulation parameters. Modulation is used to limit neural adaptation to an electrical current. Modulation may be cyclical or random (Fig. 11-27).

Question 43

Phase duration or pulse duration modulation

Answer 43

 ​Variation in the phase or pulse duration.

Question 44

Scan

Answer 44

 ​Amplitude modulation of an interferential current. Amplitude modulation of an interferential current moves the effective field of stimulation, causing the patient to feel the focus of the stimulation in a different location. This may allow the clinician to target a specific area in soft tissue.

Question 45

Sweep

Answer 45

 ​The frequency modulation of an interferential current.

Question 46

Absolute refractory period

Answer 46

 ​The period of time immediately after nerve depolarization when no action potential can be generated.

Question 47

Accommodation

Answer 47

 ​A transient increase in threshold to nerve excitation.

Question 48

Action potential (AP)

Answer 48

 ​The rapid sequential depolarization and repolarization of a nerve that occurs in response to a stimulus and transmits along the axon.

Question 49

Adaptation

Answer 49

 ​A decrease in the frequency of APs and a decrease in the subjective sensation of stimulation that occur in response to electrical stimulation with unchanging characteristics.

Question 50

Chronaxie

Answer 50

 ​The minimum duration an electrical current at twice rheobase intensity needs to be applied to produce an AP.

Question 51

Depolarization

Answer 51

 ​The reversal of the resting potential in excitable cell membranes, where the inside of the cell becomes positive relative to the outside.

Question 52

Myelin

Answer 52

 ​A fatty tissue that surrounds the axons of neurons, allowing electrical signals to travel more quickly.

Question 53

Nodes of Ranvier

Answer 53

 ​Small, unmyelinated gaps in the myelin sheath covering myelinated axons.

Question 54

Propagation

Answer 54

 ​The movement of an AP along a nerve axon; also called conduction.

Question 55

Relative refractory period

Answer 55

 ​The period after nerve depolarization in which the nerve membrane is hyperpolarized and a greater stimulus than usual is required to produce an action potential.

Question 56

Resting membrane potential

Answer 56

 ​The electrical difference between the inside of a neuron and the outside when the neuron is at rest, usually 60 to 90 mV, with the inside being negative relative to the outside.

Question 57

Rheobase

Answer 57

 ​The minimum current amplitude, with long pulse duration, required to produce an AP.

Question 58

Saltatory conduction

Answer 58

 ​The rapid propagation of an electrical signal along a myelinated nerve axon, with the signal appearing to jump from one node of Ranvier to the next (see Fig. 11-17).