Modalities Exam 2 Review Part 1 Final

Front 1

Charge (Q)

Back 1

one of the basic properties of matter, which either has no charge (electrically neutral), or may be positively or negatively charged. Measured in COULOMBS. Q = It

Front 2

electrical current (I)

Back 2

the movement or flow of charged particles through a conductor in response to an applied electrical field. measured in AMPERES.

Front 3

voltage (V)

Back 3

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. measured in VOLTS.

Front 4

resistance (R)

Back 4

a material's opposition to the flow of electrical current. Measured in OHMS.

Front 5

ohm's law

Back 5

the mathematical relationship of current, voltage, and resistance

V = IR
I = V/R

Front 6

impedance (Z)

Back 6

the total frequency-dependent opposition to current flow. Measured in OHMS. for biological systems, impedance describes the ratio of voltage to current more more accurately than resistance b/c it includes the effects of capacitance and resistance
high impedance tissues - bone, fat
low impedance tissues - muscle, nerve

Front 7

high impedance tissues

Back 7

bone, fat

Front 8

low impedance tissues

Back 8

muscle, nerve

Front 9

waveform

Back 9

a graphical representation of the current being produced by the electrotherapeutic device. the diagram of the flow of electricity is composed of a horizontal dimension representing the passage of time and a vertical dimension representing amplitude (current or voltage). the waveforms above the isoelectric line represent the flow of charged particles in one direction and the waveforms below the isoelectric line represent the flow of charged particles in the opposite direction

Front 10

continuous current

Back 10

a continuous flow of charged particles without interruptions or breaks
-DC
-AC

Front 11

Direct current

Back 11

a continuous unidirectional flow of charged particles. when two electrodes delivering direct current are placed of a patient, one electrode is always the cathode (repelling negative charge) and the other electrode is always the anode (repelling positive charge).

Front 12

alternating current

Back 12

a continuous bidirectional flow of charged particles. when two electrodes delivering alternating current are placed on the patient, the two electrodes take turns being the anode and the cathode

Front 13

pulsed current

Back 13

an interrupted flow of charged particles where the current flows in a series of pulses separated by periods when no current flows

Front 14

phase

Back 14

an episode of current flow in one direction
-monophasic
-biphasic

Front 15

monophasic current

Back 15

a series of pulses where the charged particles move only in one direction

Front 16

biphasic

Back 16

a series of pulses where the charged particles move in one direction and then in the opposite direction
-symmetrical
-asymmetrical balanced
-asymmetrical unbalanced

Front 17

biphasic symmetrical

Back 17

the charges of the phases are equal in amount and opposite in polarity, resulting in a net charge of zero

Front 18

biphasic asymmetrical balanced

Back 18

the charges of the phases are equal in amount and opposite in polarity, resulting in a net charge of zero

Front 19

biphasic asymmetrical unbalanced

Back 19

the charges of the phases are not equal, so there is a net charge

Front 20

pulse

Back 20

the combination of phases that make up a single repeatable portion of the waveform. (If the waveform is monodirectional, the phase is the same as the pulse. If the waveform is bidirectional, then the two phases together make the pulse.)

Front 21

interpulse interval

Back 21

the consistent pauses between pulses in a pulsed current.

Front 22

rise and decay time

Back 22

the rise and decay refer to the leading and trailing edge of the pulse, respectively. (A quick rising pulse is needed to excite nerves. A slow rising pulse may be too prolonged and accomodation may occur even if the amplitude of the pulse is sufficient.)

Front 23

frequency

Back 23

the number of cycles or pulses that occur in a 1 second time period. (Many clinical waveforms are not continuous, but have pulses missing in order to create interpulse intervals. These waveforms have two frequencies, their carrier frequency and their pulse frequency.)

Front 24

the pulse frequency determines...

Back 24

the characteristic muscle contraction. Lower pulse frequencies <35Hz usually cause muscle twitches. Pulse frequencies >35 Hz cause a tetanic muscle contraction

Front 25

as pulse frequencies become greater...

Back 25

the muscle tension is increased since motor units are participating more often, but at the same time the chance for muscle fatigue increases

Front 26

lower pulse frequencies have been associated w/...

Back 26

increased lymphatic return and in the release of endorphins and enkephalins for pain relief.

Front 27

period

Back 27

the period is the reciprocal of the frequency

period = pulse duration + interpulse interval

Front 28

amplitude

Back 28

the measure of the magnitude of the current or voltage. the amplitude is most often expressed as the maximum magnitude of one phase called peak amplitude. the amplitude may also be expressed as peak to peak, considering both phases.

Front 29

at low peak amplitudes...

Back 29

superficial sensory nerves will respond

Front 30

as the amplitude is increased...

Back 30

more sensory nerves will respond and the sensation will be perceived as stronger

Front 31

further increases in amplitude will...

Back 31

elicit motor nerves and as the amplitude continues to rise more motor nerves will be recruited resulting in a stronger muscle response

Front 32

total or average current

Back 32

the measurement of the flow of all of the current per unit of time. the total current is proportionate to the heat production in the tissue

Front 33

phase/pulse duration (or width)

Back 33

the phase duration measures the time of one phase, whereas the pulse duration measures the time of one pulse

Front 34

the shorter the phase duration...

Back 34

the more comfortable the stimulus is perceived. as the phase duration is shortened, skin impedance is lowered

Front 35

large diameter sensory nerves can be stimulated w/ very small...

Back 35

phase durations. as phase duration increases the motor nerves respond, then pain nerves, and finally the muscle itself. phase durations in the microseconds can stimulate nervous tissue whereas phase durations in the milliseconds are needed to stimulate denervated muscle.

Front 36

as the phase duration shortens...

Back 36

greater amplitude is needed to elicit an excitatory response

Front 37

phase/ pulse charge

Back 37

the charge delivered to the tissue during the phase or pulse. the charge of the phase is the area under the curve, and the charge of the pulse is the sum of the areas under both phases.

Front 38

the charges of a symmetrical biphasic current and balanced asymmetrical biphasic current...

Back 38

balance each other out and no net charge is delivered. unbalanced asymmetrical biphasic currents may leave minimal excess charge in the tissue

Front 39

interpulse intervals allow...

Back 39

time for the patient's tissue to dissipate any excess charge

Front 40

current modulations

modulated frequency =

Back 40

variation in the number of pulses per second delivered

Front 41

current modulations

modulated amplitude =

Back 41

variation in peak current amplitude over time

Front 42

current modulations

modulated duration =

Back 42

variation in the phase or pulse duration

Front 43

train

Back 43

a continuous sequence of mono- or biphasic pulses

Front 44

burst

Back 44

a finite train that is delivered at a specific frequency and is separated by interburst intervals

Front 45

interburst interval

Back 45

a pause in stimulation milliseconds long (too short to be perceived by the patient)

Front 46

interruption

Back 46

a pause in stimulation measured in seconds (perceived by the patient)

Front 47

on:off ratio

Back 47

the ratio of time the stimulus is on versus the interruption (off) time.

Front 48

duty cycle

Back 48

the percent of time that the current is on out of the total cycle time.

Front 49

ramp up/ ramp down

Back 49

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 the on time gradually be sequentially higher than the previous pulse. The ramp down time is the time it takes for the current amplitude to decrease from its maximum during the one time back down to zero at the beginning of the off time.

Front 50

interferential current

Back 50

the waveform produced by the interference of two medium frequency sine ACs of slightly different frequencies. these two waveforms are delivered through two sets of electrodes though separate channles in the same stimulator. the electrodes are configured on the skin so that the two ACs intersect. when the currents intersect, they interfere, producing a higher amplitude when both currents are in the same phase and lower amplitude when the currents are in opposite phases.

Front 51

IFC:

beat

Back 51

envelope of pulses formed when the two ACs intersect. the beat frequency is equal to the difference between the frequencies of the two original ACs

Front 52

IFC:

static interference (target)

Back 52

the area where the amplitude reaches its maximum remains static as long as the electrodes or the electronic components are unchaged

Front 53

IFC:

scan

Back 53

the stimulator "scans" the area by modulating the amplitude in circuit 1 between 50% and 100% of the present amplitude and maintaining circuit 2 at 75% of the max amplitude of circuit 1. this causes the area of maximum interference to rotate and the patient perceived the stimulation as moving or covering a larger area

Front 54

IFC:

sweep

Back 54

the frequency changes cyclically so that the beat can modulate between high and low rate settings

Front 55

IFC:

premodulated current

Back 55

similar to interferential, but the beats are formed within the stimulator rather than subcutaneously

Front 56

resting membrane potential

Back 56

the electrical difference between the inside of an excitable cell and the outside when the cell is at rest, usually 60 to 90 mV with the inside being negative relative to the outside

Front 57

depolarization

Back 57

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

Front 58

action potential

Back 58

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

Front 59

absolute refractory period

Back 59

the period of time immediately after nerve depolarization when no action potential can be generated

Front 60

relative refractory period

Back 60

the period after nerve depolarization in which the nerve membrane is hyperpolarized, and a greater stimulus is required to produce an action potential

Front 61

propagation

Back 61

the movement of an action potential along a nerve axon

Front 62

myelin

Back 62

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

Front 63

nodes of ranvier

Back 63

small, unmyelinated gaps in the myelin sheath covering myelinated axons

Front 64

saltatory conduction

Back 64

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

Front 65

rheobase

Back 65

the minimum current amplitude w/ a long pulse duration required to produce an action potential

Front 66

chronaxie

Back 66

the minimum duration an electrical current at twice rheobase intensity needs to be applied to produce an action potential.

Front 67

sensory nerve stimulation pulse duration =

Back 67

short pulse duration (<80μs), low current amplitude

Front 68

motor nerve stimulation pulse duration =

Back 68

long pulse duration (150 - 350 μs), high current amplitude

Front 69

motor point

Back 69

the place where an electrical stimulus will produce the greatest contraction w/ the least amount of electricity

Front 70

denervated muscle stimulation pulse duration =

Back 70

very long pulse duration (10 ms), very high current amplitude

Front 71

accomodation

Back 71

a transient increase in threshold to nerve excitation; occurs in response to electrical stimulation with a long rise time

Front 72

adaptation

Back 72

a decrease in the frequency of action potentials and a decrease in the subjective sensation of stimulation; occurs in response to electrical stimulation with unchanging characteristics

Front 73

Ionic effects:

currents which leave NO CHARGE in tissue, do not produce ionic effects

Back 73

examples:
-AC
-Pulsed - symmetrical biphasic
-Pulsed - asymmetrical balanced biphasic

Front 74

Ionic effects:

currents which leave charge in tissue, produce ionic effects

Back 74

examples:
-DC
-Pulsed - monophasic
-Pulsed - asymmetrical unbalanced biphasic