foundations- final Flashcards
1
Q
early E stim research lead to 3 main areas:
A
electrotherapy to treat disease
electrodiagnosis (interpreting the response of nerve and mm to stim)
EMG- electromyography measuring the activity of MU
2
Q
EMS
A
electrical muscle stimulation (done to maintain muscle viability)
3
Q
NMES
A
neuromuscular electrical stimulation (stimulating innervated mm to restore function. includes strengthening and muscle re-education)
4
Q
FES
A
functional electrical stimulation (often used interchangeably with NMES) includes pacemakers, orthotic stim, brain stim for function
5
Q
TENS
A
transcutaneous electrical nerve stimulation (pain management through skin electrodes)
6
Q
IFC
A
interferential current (4 electrodes, used for pain. 2 currents, interfering)
7
Q
10 basic facts on atoms and shit.
A
- atoms are electrically neutral
- positive charge of the proton in the nucleus is balanced by the negative electrons
- electrons move around the atom in spherical shells
- atoms become ions when they are not neutral
- this occurs through the gain or loss of electrons
- all atoms want to be stable or neutral
- a positive charged ion (lacking electron) seeks to gain an electron and opposite for a negative ion (get rid of an electron!)
- all matter is composed of ions and atoms
- the movement of ions creates an electrical field
- some atoms are more reactive than others (if the outer shell is full, it is less reactive)-if it can donate or receive electrons, it tends to be very reactive
8
Q
how are the maximum number of electrons in each shell calculated?
A
The shells are numbered outward from the nucleus. The maximum number of electrons found in each shell can be calculated by: 2n2 where “n” is the number of the shell.
9
Q
sodium…
A
highly reactive, ;)
10
Q
conductors and insulators
A
-conductors are made out of materials that are composed of reactive atoms
-insulators are materials with atoms that have stable shells
fat and skin are good insulators
nerves and muscles are good conductors
11
Q
characteristics of electricity
A
- a form of energy
- when in motion, exhibit magnetic, chemical, mechanical, and thermal effects and when at rest or in motion, exerts force on other electricity
- electric current is the actual flow of electrons in a conductor
- electrons flowing continuously in 1 direction is called Direct Current (DC)
- periodic reversal of electron flow is called Alternating Current (AC)
12
Q
more characteristics of electricity
A
- charge is the number of free electrons flowing (measured in coulombs)
- current (I) how fast electrons flow. the ampere (A) is the unit of measuring the rate of flow.
- therapeutic current flow is measured in mA and uA
- voltage (V) the electromotive force (EMF) produced by an electrical potential. electron flow is from negative to positive.
- resistance (R) ease or difficulty of current moving through substances. all materials offer some resistance to current flow. Ohm is measure of resistance.
13
Q
even more characteristics of electricity
A
impedance- opposition of electrical circuits to flow of AC. Ohm is used for impedance and resistance.
- tissue impedance varies throughout body. more water and more ions means more conductance.
- wet skins conducts more easily. duh.
14
Q
Ohm’s law!
A
- relationship between current, voltage, and resistance (impedance)
- V=IxR
- current flow (I) is directly proportional to voltage
- current and resistance are inversely related. high skin resistance therefore required more voltage to produce necessary current.
15
Q
current flow
A
- 2 types of electrical currents and the body: electron flow (from the unit to the body) and ionic flow within the body
- in the body, multiple ions are acted upon by an electrical charge
- under the positive pole (anode), positive ions such as sodium are driven to the negative pole. negative ions such as chloride are driven to the positive pole.
- as the positive ions are driven toward the cathode, NaOH is formed, creating an alkaline environment.
- as negative ions are driven toward the anode, an acidic environment is created (HCl).
- as the body attempts to balance pH, circulation increases!
16
Q
current classification: direct current
A
- one electrode is always positive and one is always negative
- one electrode receives current from the machine and current is returned to the machine by the other electrode
- current can be continuous or pulsed. as ions gather under one electrode, a chemical environment is created.
17
Q
current classification: alternating current
A
- uninterrupted, bi-directional flow of charged particles. changes direction at least once per second
- each electrode is positive for one phase and then negative for the other
18
Q
pulsatile current
A
- unidirectional or bi-directional flow of charged particles periodically ceasing for a period of less than one second before the next electrical event
- current is comprised of individual pulses rather of short duration. each pulse is comprised of one or more phases.
- electrochemical reaction depends on whether the pulse is DC or AC
19
Q
electrical parameters
A
waveform- visual representation of the pulse
- pulses are monophasic and biphasic
- a monophasic pulse has one phase. this pulse is always unidirectional. (+ve or -ve)
20
Q
biphasic waveform
A
- most TENS units and NEMS are biphasic waveform
- biphasic is better than monophasic at preventing ion build-up and abnormal pH
21
Q
amplitude
A
- peak amplitude is the maximum current delivered in one phase
- higher peak amplitudes allow for deeper penetration into tissue
22
Q
-E-stim is capable of generating 4 levels of stimulation:
A
subsensory, sensory, motor, noxious (less current to more)
23
Q
rise time
A
the time it takes for amplitude to increase from zero to peak amplitude
24
Q
decay time
A
time it takes for peak amplitude to decrease back to zero
25
pulse width
- duration of a pulse wave
| - the longer the pulse wave, the more likely you are to stimulate motor neurons
26
sensory nerves are more stimulated by...
low (short) pulse width
27
frequency
as the frequency increases, one moves from twitch to tetany
28
therapeutic frequency range:
1-120 hZ
29
duty cycle
ratio of on/off time (1:4) IMPORTANT FOR REST
30
RAMP TIME (rise time)
time for the pulse train to reach maximum amplitude (rise time is time of phase to reach max)
31
ramp time affects..
comfort. 2 seconds is common
32
Relationship between pulse width and frequency
- pulse width is the duration of a pulse
- pulse width and frequency have an inverse relationship
- as frequency increases, pulse width decreases
33
for example...
- a tens unit can be set to fire once every second (1Hz).
| - within that second, the length of firing can be adjusted to be delivered in different length patterns.
34
firing can be made up of a series of impulses:
of 0.2ms duration or 0.07ms.
35
at 0.2ms...
there will be less impulses in the train duration of firing
36
at 0.07ms ...
there will be substantially more impulses.
37
frequency and pulse width
If we wanted a higher frequency (more pps), we would have to have a lower pulse width.
38
modulation
to vary one or more of the electrical parameters
| eg. amplitude and duration can be modulated
39
modulation prevents..
accommodation
40
what does TENS do and how?!
treats pain via gating
41
what can you adjust on a TENS unit?!3
frequency
pulse width
amplitude (dials on top) intensity
42
e stimulation indications
- muskuloskeletal, urologic, neurologic systems
- pain management, muscle strengthening, stimulation of denervated muscle
- wound care, fracture healing, promotion of circulation, edema management
43
contraindications
```
pregnancy- over the uterus
pacemaker- not over
-cancer- not over cancer site
-not on or near DVT
-not over carotid artery
```
44
precautions
obesity
can exacerbate eczema, psoriasis, acne, dermatitis
presence of material
45
safety considerations.. what is a lethal current?!
between a 100 and 200 mA
46
Physiologic reactions to intensities follows the progression of: ...6
sensation, muscle contraction, pain, fibrillation, defibrillation and burns
47
Electrical “shock” is first felt as tingling at
1mA
48
Motor response occurs at
5mA
49
An inability to let go occurs
around 20 mA
50
Ventricular fib –
80 mA.
51
Vent defib –
6A
52
burns at
12A
53
pretreatment guidelines4
ask about CI's
inspect skin
sensation check
ask history of E-stim
54
during treatment guidelines
give patient on instructions for what to expect:
should feel light tingle
will then turn up to comfortably strong (TENS)
if using NMES, need to see contraction
tens-20 minutes
nmes- exercise with on
give the patient a bell ***
55
post treatment guidelines
- ask patient how they feel
- inspect skin
- document
- home use?
56
physiologic basis of nerve and muscle excitation
- nerve and muscle cells are exciteable (bone and fat cells are not)
- exciteable means that they have the ability to have their cell membranes altered to allow ionic changes in the potential across the membrane
- this can occur in response to thermal, mechanical, chemical, or electrical change
57
when at rest...
negative inside, positive outside
| sodium pump keeps the sodium out!
58
resting membrane potential (RPM)
- all living cells have membranes capable of separating electrical charges
- excitable cells do this in a greater magnitude (-60mV to -90mV)
- inside of these cells.. relatively negative
- ion concentrations are unbalanced between inside and outside... they want to be balanced..
- the cell membrane acts as a barrier to Na+ while allowing K+ to move easily. this sets up the RMP to nearly equal the equilibrium potential of K+ -90mV
59
more on the pump
...sodium pump works to keep the sodium outside of the cell
given a stimulus, the cell will allow some Na+ to enter. this causes depolarization to occur. if enough Na+ enters, then the threshhold will be reached.
reaching the threshhold causes a rapid reversal of polarity. this is called an action potential.
the action potential only lasts about 1-2 milliseconds but it is long enough to flip the polarity from -70mV to +35mV
60
still continued.....
once the stimulus is gone, the Na+ pump begins to pump out the sodium to restore it the membrane potential about to -70mV.
there is a brief period called hyperpolarization, where the RMP reaches -90mV before re-setting to -70mV.
the depolarization phase of the AP is called the absolutely refractory period- this means that the cell will not respond to another stimulus at this time.
it cannot respond until repolarization. the cell reached action potential according to "All or none". meaning it either reaches AP or it doesn't.
61
random questions
what are the parts to a neuron? what is saltatory conduction?
62
peripheral nerves
three categories:
A (Biggest, afferent, efferent, and myelinated)
B (same as A but smaller)
C unmyelinated and small-- these are pain (visceral) and cutaneous sensation
63
more on the peripheral nerves
bigger is faster
faster has lower threshhold
since these nerves (A, B,C) often travel together, it is common that external stimulation of one, stimulates the other!
stimulation of large motor fibers can lead to pain stim if stimulus is long enough.
64
what happens when a nerve is stimulated?
-when a nerve is stimulated, a reversal of polarities begins and proceeds in both directions
65
the distance that the AP spreads is dependent on what?
the size of this nerve fiber, resistance of the membrane, and axon resistance
66
large myelinated fibers...
permit a fast signal that travels a great distance (nodes of ranvier definitely help too)
67
what is a motor unit?
a motor nerve and all the muscle fibers attached to it
68
where are small motor units found?
in muscle requiring FMC (facial)
| they have a small ratio of nerve to fibers
69
t tubules?
a deep invagination of the sarcolemma, (which is the plasma membrane of skeletal muscle and cardiac muscle cells). These invaginations ***allow depolarization of the membrane to quickly penetrate to the interior of the cell.
70
The sarcoplasmic reticulum is ...
... a specialized type of smooth ER (endoplasmic reticulum) that ***regulates the calcium ion concentration in the cytoplasm of striated muscle cells.
71
What is neurotransmitter?
a substance (as norepinephrine or acetylcholine) that transmits nerve impulses across a synapse—see false neurotransmitter.
72
What is the function of calcium? Where does it attach?
Upon nervous system excitation for a contraction, calcium is released into the fiber. It binds with troponin and stimulates it to move tropomyosin, exposing the binding site for the myosin crossbridge.
73
talk bout tetany
a summation of twitches
| if successive twitches (one muscle fiber contraction) occur successively, we have tetany
74
motor recruitment
- strength of contraction increases as more motor units are recruited.. makes sense
- increasing amplitude leads to the stimulation of more motor units
75
what happens when we voluntarily recruit muscles?
we recruit small motor units - type 1 first.
| large motor units are recruited as needed.
76
motor recruitment.. what happens when we stimulate with electrical stim?
the order is reversed...large superficial motor units are recruited first.
-the reversal of recruitment and the firing of large motor units first is fatiguing
77
what affects how much a stimulus is needed for depolarization?
the resistance and capitance properties of an excitable cell
.. therefore,if a stimulus is applied for too short of a time or is not intense enough, stimulation will not occur
-different nerves have different levels of stimulation required to reach threshhold
78
what does A alpha respond to?
short duration and low intensity
79
5 principles to E stim
- positive pole is the anode
- negative pole is the cathode
- like charges repel and opposites attract
- cathode is often called the active electrode because the positive ions gather under the cathode, making the outside of the cell negative (depolarized). (Na+ and K+ move to the cathode).
- anode is often called dispersive electrode.
80
principles of impedance
-skin and fat are good resistors to current flow
-more intensity is required to stimulate glutes (more fat) compared to biceps
-impedance (resistance) can be lessened by warming and wetting the area
...remove body hair..use gel or self-adhering electrodes
81
current density
- inverse relationship between current density and size (electrode)
- smaller electrodes permit deeper penetration
- size of electrode will also determine which mm are more likely to be stimulated
- to stimulate quads, one needs a large electrode.
- to stimulate peroneus longus, smaller
- spread of electrodes also effects current density.
- the further the spread, the deeper the penetration
