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Electro > Exam One > Flashcards

Exam One Flashcards

1
Q

voltage (v)

A

driving force between charged particles
measured in volts

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2
Q

current (I)

A

movement of charged particles in response to an electric field or voltage
measured in amps

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3
Q

T or F: a voltage excites tissues

A

F: a current does

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4
Q

resistance (R)

A

opposition to direct current flow
measured in ohms

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5
Q

as voltage goes up, current goes ___

A

up

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6
Q

as resistance goes up, current goes _______

A

down

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7
Q

phase change

A

area under a single phase form, time integral of a current for a single phase

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8
Q

pulse charge

A

time integral for the current waveform over the entire pulse

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9
Q

frequency

A

rate at pulses of current are delivered

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10
Q

period

A

time from start of one pulse to the start of another

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11
Q

frequency =

A

1 second/period

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12
Q

period =

A

1 second/frequncy

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13
Q

what is direct current and what is it used for?

A

one way flow of charged particles
used for iontophoresis

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14
Q

what is alternating current and what is it used for?

A

bidirectional flow of charged particles
used for electrical stim for pain management

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15
Q

what is pulsed current and what is it used for?

A

interrupted mono or bidirectinoal flow of charged particles used for muscle recruitment and TENS

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16
Q

sodium-potassium pump

A

use one ATP to pump 3 sodium out and 2 potassium into the cell

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17
Q

what do you have to have to generate an action potential

A

depolarization of the membrane

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18
Q

orthodromic propagation of an action potential

A

AP goes in the normal direction of a nerve

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19
Q

antidromic propagation of an action potential

A

AP goes in the opposite physiologic direction than normal

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20
Q

T or F: an electrically stimulated action potential travels both directions

A

T

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21
Q

Higher membrane resistance = _____ AP propagation

A

faster

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22
Q

large diameter neurons conduct APs ________ than small diameter neurons

A

faster (b/c they have less internal resistance)

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23
Q

myelination ___ membrane resistance for ______ conduction of APs

A

increases, faster

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24
Q

Axons with higher membrane resistance are _____- to stimulate than those with lower membrane resistance

A

harder, takes longer to depolarize

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25
Q

space constant

A

how far a current will spread inside a neuron
the larger space constant, the further the current will flow

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26
Q

membrane resistance ______ space constant

A

increases, b/c less of the current leaks out

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27
Q

if longitudinal resistance is low, the space constant _____. So, do large or small diameter neurons have a larger space constant?

A

increases
large

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28
Q

time constant

A

time it takes for a membrane to reach 63% of the final voltage
T = membrane resistance * membrane capacitance

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29
Q

the large a neuron the _______ it is to stimulate

A

easier

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30
Q

what neurons are stimulated first (sensory, motor, or pain) and why?

A

sensory because they are more superficial

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31
Q

capacitance

A

ability of a membrane to store a charge

32
Q

myelin _____ capacitance

A

decreases

33
Q

high capacitance ______ the time it takes to depolarize a cell

A

increases

34
Q

most excitable and fastest conducting neurons

A

myelinated large diameter fibers

35
Q

rank diameter of pain, motor, and sensory nerve fibers from largest to smallest

A

motor > sensory > pain

36
Q

what two factors influence phase charge (area under the curve)

A

amplitude and time (pulse duration)

37
Q

as you decrease the amplitude, you have to _____ the pulse duration to get the same effect

A

increase

38
Q

recruitment order for clinical e-stim contraction

A

sensory > motor> pain * because sensory nerves are closer to the surface

39
Q

size principle for volitional muscle recruitment

A

smallest to largest

40
Q

how is the size principle different in e-stim

A

surface electrode stimulation recruits a combo of all 3 motor neuron types at the same time. it recruits large fibers before small but it also depends on what is closest to the electrode

41
Q

rheobase

A

minimum amplitude of current of infinitely long pulse duration that will effect a response

42
Q

chronaxie

A

pulse duration that will elicit a response 2x the rheobase amplitude

43
Q

where would denervated muscle fall on a strength-duration curve?

A

really far right
you have to have a much larger amplitude and longer duration

44
Q

what parameters influence e-stim response?

A

frequency, pulse width, on/off time, wave form, ramp time

45
Q

intensity and pulse duration will determine the ___ of nerve and muscle fibers activated in response to a stimulus

A

number

46
Q

what physiological response are we affecting by adjusting the intensity of stimuluation?

A

the amount of depolarization more fibers are recruited

47
Q

increasing pulse duration ______ intensity

A

increases
(by increasing phase charge)

48
Q

how does increasing frequency affect the muscle response?

A

it increases the force by making the already active motor units fire harder ** it DOES NOT recruit more motor units

49
Q

how do yo increase force production from active motor units

A

increase frequency

50
Q

the smaller the electrode the _______ the current density

A

greater
greater the current density, the greater the response

51
Q

monopolar electrode

A

single stimulating (smaller) electrode placed over target tissue and dispersive electrode (larger) placed in a remote location *good for NMES

52
Q

bipolar electrode

A

both surface electrodes from a stimulator channel are placed over the target area
electrodes are equal size

53
Q

quadripolar electrode

A

placement of electrodes from two stimulation channels in the target area the currents interact with one another used in interferential stimulation, common for pain control

54
Q

what type of stimulator poses the greatest risk of burning a patient?

A

constant current

55
Q

rate coding

A

increasing the rate of firing on already active motor units

56
Q

where is calcium stored for muscle contraction

A

sarcoplasmic reticulum

57
Q

What do t-tubules do?

A

allows signal to get deeper into the fiber

58
Q

thin filament

A

actin

59
Q

thick filament

A

myosin

60
Q

troponin

A

regulates tropomyosin

61
Q

tropomyosin

A

covers myosin binding sites

62
Q

type I muscle fibers

A

slow twitch, fatigue resistant

63
Q

type IIa muscle fibers

A

fast twitch, fatigue resistant

64
Q

type IIb muscle fibers

A

fast twitch, fatigable

65
Q

cross bridge cycling

A
  • myosin head attaches to actin binding site, forming cross-bridge
  • myosin cross-bridge pulls thin filament toward center of sarcomere
66
Q

what neurotransmitter starts an AP?

A

Acetylcholine

67
Q

what causes the rapid change in membrane potential during depolarization

A

influx of sodium

68
Q

what four factors influence muscle force production?

A

1) temporal summation (frequency of activation)
2) number of fibers activated
3) length of skeletal muscle
4) velocity/direction of contraction

69
Q

goal of neuromuscular electrical stimulation

A

muscle activation
*limited functional application

70
Q

goal of functional electrical stimulation

A

assist with performance of functional tasks

71
Q

3 downsides to electrical stimulation of muscle

A

1) increased discomfort
2) earlier fatigue
3) increased change of muscle damage

72
Q

What frequency is typically used for NMES?

A

30-50 Hz

73
Q

what does a higher frequency cause? what is it better for?

A

causes greater fatigue
better for endurance training

74
Q

what 3 things does increasing amplitude lead to?

A

increased motor unit recruitment
increased torque production
increased pain and fatigue

75
Q

what duty cycle is typically used in a rehab setting?

A

1:5
10 seconds on, 50 off

Electro (5 decks)

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