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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
space constant
how far a current will spread inside a neuron the larger space constant, the further the current will flow
26
membrane resistance ______ space constant
increases, b/c less of the current leaks out
27
if longitudinal resistance is low, the space constant _____. So, do large or small diameter neurons have a larger space constant?
increases large
28
time constant
time it takes for a membrane to reach 63% of the final voltage T = membrane resistance * membrane capacitance
29
the large a neuron the _______ it is to stimulate
easier
30
what neurons are stimulated first (sensory, motor, or pain) and why?
sensory because they are more superficial
31
capacitance
ability of a membrane to store a charge
32
myelin _____ capacitance
decreases
33
high capacitance ______ the time it takes to depolarize a cell
increases
34
most excitable and fastest conducting neurons
myelinated large diameter fibers
35
rank diameter of pain, motor, and sensory nerve fibers from largest to smallest
motor > sensory > pain
36
what two factors influence phase charge (area under the curve)
amplitude and time (pulse duration)
37
as you decrease the amplitude, you have to _____ the pulse duration to get the same effect
increase
38
recruitment order for clinical e-stim contraction
sensory > motor> pain * because sensory nerves are closer to the surface
39
size principle for volitional muscle recruitment
smallest to largest
40
how is the size principle different in e-stim
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
rheobase
minimum amplitude of current of infinitely long pulse duration that will effect a response
42
chronaxie
pulse duration that will elicit a response 2x the rheobase amplitude
43
where would denervated muscle fall on a strength-duration curve?
really far right you have to have a much larger amplitude and longer duration
44
what parameters influence e-stim response?
frequency, pulse width, on/off time, wave form, ramp time
45
intensity and pulse duration will determine the ___ of nerve and muscle fibers activated in response to a stimulus
number
46
what physiological response are we affecting by adjusting the intensity of stimuluation?
the amount of depolarization more fibers are recruited
47
increasing pulse duration ______ intensity
increases (by increasing phase charge)
48
how does increasing frequency affect the muscle response?
it increases the force by making the already active motor units fire harder ** it DOES NOT recruit more motor units
49
how do yo increase force production from active motor units
increase frequency
50
the smaller the electrode the _______ the current density
greater greater the current density, the greater the response
51
monopolar electrode
single stimulating (smaller) electrode placed over target tissue and dispersive electrode (larger) placed in a remote location *good for NMES
52
bipolar electrode
both surface electrodes from a stimulator channel are placed over the target area electrodes are equal size
53
quadripolar electrode
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
what type of stimulator poses the greatest risk of burning a patient?
constant current
55
rate coding
increasing the rate of firing on already active motor units
56
where is calcium stored for muscle contraction
sarcoplasmic reticulum
57
What do t-tubules do?
allows signal to get deeper into the fiber
58
thin filament
actin
59
thick filament
myosin
60
troponin
regulates tropomyosin
61
tropomyosin
covers myosin binding sites
62
type I muscle fibers
slow twitch, fatigue resistant
63
type IIa muscle fibers
fast twitch, fatigue resistant
64
type IIb muscle fibers
fast twitch, fatigable
65
cross bridge cycling
- myosin head attaches to actin binding site, forming cross-bridge - myosin cross-bridge pulls thin filament toward center of sarcomere
66
what neurotransmitter starts an AP?
Acetylcholine
67
what causes the rapid change in membrane potential during depolarization
influx of sodium
68
what four factors influence muscle force production?
1) temporal summation (frequency of activation) 2) number of fibers activated 3) length of skeletal muscle 4) velocity/direction of contraction
69
goal of neuromuscular electrical stimulation
muscle activation *limited functional application
70
goal of functional electrical stimulation
assist with performance of functional tasks
71
3 downsides to electrical stimulation of muscle
1) increased discomfort 2) earlier fatigue 3) increased change of muscle damage
72
What frequency is typically used for NMES?
30-50 Hz
73
what does a higher frequency cause? what is it better for?
causes greater fatigue better for endurance training
74
what 3 things does increasing amplitude lead to?
increased motor unit recruitment increased torque production increased pain and fatigue
75
what duty cycle is typically used in a rehab setting?
1:5 10 seconds on, 50 off

Electro (5 decks)

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