clin pro 2 exam 1

what is the fundamental underlying property of electromagnetic force?

electrical charge

how do you obtain an electrical charge?

addition or removal of electrons

what are the units of electrical charge?

coulomb

what is ionization?

process by which atom or molecule acquires charge

what is the atom of a molecule that has gained or lost an electron?

ion

cation

more protons or electrons?

how does it become charged?

positive ion

protons > electrons

becomes positively charged by LOSING electrons

anion

more electrons or protons?

how does it become charged?

negative ion

electrons > protons

becomes negatively charged by GAINING electrons

what is polarity?

net charge of an object

cathode =?

excess electrons or negative charges

anode =?

deficiency of electrons or negative charges

what is the driving force to move electrons?

3 options:

units?

voltage

electrical potential energy

electromotive force

V or mV

blank blank establishes a voltage force:

this allows cells to depolarize and initiate or transmit electrical signals by the movement of ions

electrical potential

what is electrical current?

movement of ions or electrons in a conductor in response to a voltage force

T or F:

Voltage has an indirect correlation with the flow of current

false

direct correlation

voltage units?

milliamp (mA)

microcurrent (< 1 mA) = microampere

in which direction do electrons flow?

from greater concentration of electrodes to lesser concentration of electrodes

ion flow:

anions ( ) → ( )

cations ( ) → ( )

anions (-) → anode (+)

cations (+) → cathode (-)

magnitude of current flow is ___ proportional to voltage F and quantity of charge moving

directly

what is resistance?

examples?

opposition to flow of current

skin, fat, hair, bone, tendon, fascia, ligament, callus, scar

capacitance

degree to which electrical charge is stored in a system

ohm’s law:

I = V / R

I = current

V = voltage

R = resistance

current is ___ proportional to V pushing the current

directly

current is ___ proportional to resistance to voltage F

indirectly

unit for resistance?

ohm

what is a capacitor

stores charge in an insulator within a current field

capacitance determines how ___ a neuron’s membrane potential will respond to input

quickly

capacitance is influenced by:

3 things

thickness + composition of membrane

presence of specific ion channels

concentration of ions inside and outside of cell

does capacitance stay the same?

no, it can change over time

capacitance unit?

farad

do muscular or nervous neurons have a greater capacitance?

what does this mean?

muscular

requires more ions to be moved per change in voltage

smaller = faster

larger = slower

why does abruptly turning machine off cause electric shock in patient?

turning machine off makes the machine become the capacitor (stores charge), but since it doesn’t have anywhere to go, it just discharges to the patient

impedance vs resistance

impedance = resistance to flow of ALTERNATING current

resistance = specific to DIRECT CURRENT

what do gels and adhesive agents on electrodes do?

in terms of conductivity and impedance

increases conductivity by DECREASING impedance

resisters/insulators VS conductors

examples?

resistors/insulators = materials that cause an INCREASED resistance to flow (not watery stuff like rubber/plastic, fat/myelin, skin, bone)

conductors = causes DECREASED resistance to flow (watery stuff like msc, N, fluid, gas, soln, metals, water)

is moist or dry skin increase resistance to current flow?

dry skin can INCREASE resistance

what is the most common form of current used for electrotherapeutics?

why?

pulsed current

low risk for adverse response

what are the 2 fundamental electrical currents?

are these the most commonly used?

AC and DC

no, they have a higher risk for adverse response vs pulsed

what is a waveform?

depiction of characteristics that represent a given current?

what line demonstrates the magnitude of a current wrt the ___ line

is it horizontal or vertical

units?

isolelectric

horizontal

amps, mA, V

peak amplitude

highest current or voltage reached in a phase

greater auc = ___ effect

greater

what is the frequency or pulse rate?

units?

rate at which current changes directions on isoelectric line

hertz for AC

will a line that doesn’t cross the isolelectric line have a frequency?

NO; if it doesn’t cross, frequency = 0

if it DOES, then it will have frequency

what is the frequency for direct current?

0

what is direct current?

continuous, uni-directional flow of ions or electrons for at least 1 second

what are the clinical uses for DC?

iontophoresis

wound care

what is AC?

does it need to change directions?

uninterrupted, bidirectional flow of ions or electrons

must COD at least once per secondc

clinical uses for AC?

russian

interferential

what is pulsed current?

uni or bidirectional flow of ions or electrons that periodically ceases before the next electrical event

what is a pulse

isolated electrical event separated from the next by an INTERPULSE INTERVAL

is AC or DC current interrupted?

AC

what gives time and magnitude of voltage or current?

the ___ and ___ of the pulse

duration

amplitude

why does waveform shape impact the tolerance and magnitude of effect when stimulating skeletal muscle?

different shapes will mean spending different durations of time @ peak amplitude

square vs triangle

monophasic pulsed current

pulse = ___

deviates from isoelectric line in 1 direction

phase

biphasic pulsed current

pulse = ___ + ___

deviates from isoelectric line in 2 directions

phase + phase

burst

generation of 2+ consecutive pulses separated from the next series by interburst interval

what is a duty cycle?

ratio of on and off time

(on + off) / 100

rise time

time required for the leading edge of a SINGLE PHASE to reach peak amplitude

fall time

time required for the leading edge of a SINGLE PHASE to return to isoelectric line

is current being delivered during ramp up and ramp down?

what effect does this have on the patient?

yes

long ramp times can greatly reduce the amount of current delivered to patient

how long must you spend @ peak amplitude to have 10 seconds of therapeutic effect?

needs at least 10 seconds @ peak amplitude (doesn’t include ramping)

phase charge

charge within one phase of a pulse

pulse charge

cumulative charge of ALL PHASES in a pulse

phase charge is a critical determinant of the magnitude of physiological effects when trying to activate ___ ___

skeletal muscle

in monophasic pulses,

pulse ___ charge

pulse = charge

biphasic symmetrical pulses

amplitude + duration of 1st vs 2nd phase

can this have a charge?

sum of amplitude and duration of first and second phases are EQUAL

NO

biphasic asymmetrical

amplitude and duration relationship?

can this have a charge?

differ

sum of amplitude + duration doesn’t equal 0

YES

CV vs CC

which is better?

CV = voltage F driving current remains constant

CC = constant current despite varying biological resistances

CC

continuous vs synchronous NMES TENS

continuous wont usually have on/off time

synchronous will usually have on/off timet

transcutaneous vs percutaneous

transcutaneous = on skin (electrode pads)

percutaneous = under skin

metal vs flexible electrodes

metal = increased risk of burns
needs gel or wet sponge between metal and tissue

flexible = risk of allergic rxns

subjective reasons to replace electrodes (3)

1. decreased sensation or change in perceived quality of stimulus

2. acute sensations (prickly, burning, stinging)

3. hot spot

objective reasons for replacing electrodes (3)

1. skin more red than usual

2. electrode integrity compromised

3. decreased physiological response

should you use alcohol based cleansers for cleaning skin before electrode application?

no, because dry skin can INCREASE RESISTANCE

purified or tap water for metal electrodes?

tap conducts better

will a bigger or smaller electrode provide a stronger stimulus?

small = stronger stimulus

increased density

what 2 factors determine what electrode size you choose?

goal of tx

area to be stimulated

dermatomal electrode placement

skin → nerve root

myotomal electrode placement

msc → nerve root

sclerotomal electrode placement

bone → nerve root

what does it mean when you get a muscle twitch when using e-stim?

what is the exception to this?

muscle twitch = activating NERVE

only time sarcolemma activated before nerve is if there’s DENERVATION

does neurolemma or sarcolemma have a lower threshold for activation?

neurolemma

the area demonstrating the greatest response to current = ?

functional motor point

where should you typically place electrodes?

proximal 3rd of msc belly

electrode placement for motor stim?

active vs dispersive electrode

active electrode on functional motor point

dispersive electrode on or near muscle mass

wider vs narrow spacing for electrode placement?

wider = deep

narrow = superficial

what can happen if electrodes come into contact with each other?

increased current density

nmes vs tens:

motor vs sensory fibers?

nmes = motor

tens = sensory

what electrode type is best for strengthening?

bipolar placement

what placement is best for tissue healing?

monopolar

best placement for pain?

quadripolar

sources of thermal hazards?

solutions?

short circuit

overloaded circuit

fuses and circuit breakers

what is the most common source of shock?

faulty or worn out insulation

GFCI

what threshold before it activates?

ground fault circuit interrupter

detects any loss or leak of current

3-5 mA

what 3 effects of current electricity?

chemical

thermal

physical

migration phase of electrochemical effects?

NA+ migrates toward cathode

CL- migrates toward anode

which chemical rxn causes hardening vs softening?

anode vs cathode

which is stronger?

anode = hardening (sclerotic) effect

cathode = softening (sclerolytic) effect

cathode

are the variables in joule’s law directly or indirectly proportional?

all directly proportional

why do people have redness post tx?

joules law

heat is lost when transferring from one source to the next

is there net negativity or positivity at rest in intracellular environment?

negativity