lecture 3: principles of electrical stimulating currents Flashcards
what are atoms that contain a positive (+) or negative (-) charge
ions
what is the unit of measure that indicates the rate at which electrical current flows
ampere
what is current described in
milliamperes (1/1000 ampere); or in microamperes (1/1,000,000 ampere)
what is the force resulting from an accumulation of electrons at one point in an electrical circuit, usually corresponding to a deficit of electrons at another point in the circuit
voltage
what is a resist current flow; fewer free electrons and greater resistance to electron flow
insulator
which law is the current in a circuit is directly proportional to the voltage and inversely proportional to the resistance
ohm’s law
Resistance of electrical flow depends on the characteristics of the ___
conductor
for electricity explained what is the resistance , the force and the flow
the force is the volt
the flow is the amp
the resistance is the ohm
is fat a conductor or insulator
great insulator
is the nerves a conductor or insulator
good conductor
what is the best electrical conductor in the body
blood
is a tendon a conductor or insulator
poor conductor
is a muscle a conductor or insulator
good conductor
what is the poorest conductor in the body
the bone
is the skin a conductor or insulator
insulator
what has the most resistance in the body (so good insulator)
tendon , ligament , bone and fat
what in the body has the least resistance (so good conductor)
nerves , blood and muscles
does frequency equal intensity
no
what is the correlation between electrical impedance vs frequency
as frequency goes up the impedance goes down
what are examples of alternating current
biphasic , TENS , IFC
how do electrons move in alternating currents
negative to positive
for alternating currents it is Neutralizes chemical reactions if “____ ”
balanced
what is direct current also called
galvanic current and monophasic
what is Uninterrupted unidirectional flow of electrons toward the positive pole (anode)
direct current
what is accumulated at each electrode for a direct current
chemicals
what is an example of direct current
iontophoresis
Instead of being one solid block of current, the current can be broken up into parts.. what is this called
pulses
what is pulsatile electrotherapeutic current
2 or more pulses grouped together
what is the direction of pulsatile current
could be unidirectional or bidirectional
what is most nerve/muscle stimulation currents
hi volt and russian currents
are pulsatile and hi volt and russian current continous or discontinuous
discontinuous
what in the body does not know the difference between AC and DC
nerves
with a continuous direct current when would a mm contraction occur
only when then current intensity rose to a stimulus threshold
Once the membrane repolarized, what would be needed to force another depolarization and contraction
another change in the current intensity
what is this called a fiber has been subjected to a constant level of depolarization will become unexcitable at that same intensity (amplitude).
accommodation phenomenon
what is the biggest difference in DC and AC
is the ability off direct current to cause chemical changes
Chemical effects from using direct current usually occur only when?
stimulus is continuous and is applied over a period of time (> 1 minute)
how is the resistance and current flow in a series electrical circuit
higher resistance and lower current flow
what are examples of series in the body
skin and fat
how is the resistance and current flow for a parallel electrical circuit
lower resistance and higher current flow
what are examples of parallel electrical circuits in the body
nerves, blood , mm , connective tissue and bone
what is the ion flow path
path of least resistance
is the path of least resistance the shortest path
not really
in electrical terms what is the frequency
how many cycles per second
in electrical terms what is intensity
increasing the stimulation or amplitude
in electrical terms what is pulse duration
changing the current pulse length to target specific structures
what is the ability of tissue to store electricity
capacitance
what is the least and more capacitance in the body
nerve is least and muscle tissue is the most
if something has a higher capacitance, how does that affect the response
longer before a response
the ___ the capacitance, the less the charge can be stored
lower
changing the ___ or the lecrode distance can change the effects of skin impedance
frequency
how can capacitance in a tissue be reduced
by increased stimulation frequency
how would u rank these from lower capacitance to highest
muscle fibers
AB
Ao
mm tissue
C
lowest) A𝛃 < A𝛅 < C < muscle fiber < muscle tissue (highest)
AC - ___ current; two separate phases during each cycle
biphasic
AC - ___ current; two separate phases during each cycle
biphasic
what applies to biphasic current; bidirectional flow during one cycle
cycle
what is an individual waveform, applies to monophasic current
pulse
DC - ____ (monophasic); current flows in the same direction either to positive or negative pole
unidirectional
what is the intensity of the current stimulation
amplitude
total current can be increased by increased what 2 things or a combo of both
increasing pulse duration or pulse frequency
how is the duration pulse with a high amplitude rather then a low amplitude
short duration compared to a longer duration
what is a monophasic pulse charge
phase charge and pulse charge are the sample and always > 0
what is the time in which a pulse goes from peak amplitude to 0 V
decay time
a fast pulse rise will have what kind of change in phase charge , ____ skin impedenace , and need ___ voltage to achieve same current flow
rapid change
lower
less
what is the duty cycles
on-off time
the more “___” time then the less muscle fatigue will occur
off
what effect does the 1:1 ratio of duty cycle have on the mm
fatigues mm rapidly
what affect does the 1:5 ratio of duty cycle have on mm
less mm fatigue
what does 1:7 ratio of duty cycle mean
no fatigue (passive mm exercise)
what is called the length of time current is flowing in one cycle
pulse duration
what is the length of time current is off in one cycle
interpulse interval
____ the duration can stimulate more nerve fibers when an adequate stimulation intensity is available to depolarize the membranes
Increasing
what is the number of impulses or cycles produced by electrical stimulating device in 1 second
frequency
what can frequency determine
the type of mm contraction elicited
when does tetany occurs at
approx 55 pps (Hz)
does tetanization depend on intensity
no
Electrical impedance of the biological tissues is altered by what 3 things
the localizations and distance of the electrodes as a well as by the currents frequency
Skin impedance ____ as the inter-electrode distance increases
increases
Skin impedance ____ as frequency increases
decreases
what is a combined pulses turned on and off for a short time in a repetitive cycle
burst modulation
what modulation is a beat frequency produced by two interfering biphasic currents (AC) with different frequencies
beat modulation
what modulation currently is the best for patient’s comfort
ramping modulation
the higher the intensity means what to the current
it reaches deeper into the tissue
what is a negative electrode; highest number of electrons
cathode
what is a positive electrode; least number of
electrons
anode
what has a Designate one electrode as negative and one as positive
monophasic
what kind of polarity for mm contraction
negative active electrode
the current density much be high enough to facilitate ____
depolarization
if some electrodes are smaller then the other what happens to the current density under the smaller electrode
is increased
what does the larger electrode size mean for current density
decreased current density
how is the area of highest current density when electrodes are spaced close together
superficial
how is the area of the highest current density when the electrodes are spaced further apart
deep
where do u place the large electrode and smaller electrode
large electrode away from treatment area
smaller electrode to nerve or motor point
Larger electrode disperses current over a ____ area
large
Small electrode concentrates current over ___ ___
motor point
which electrodes are used for smaller; current density is greater
active
what electrodes are larger , current density is less
dispersive
What kind of physiology response does Cathode (-) have
alkaline effect
What kind of physiology response does Anode (+) have
acidic effect
what physiologic response to electrical current
✧ Muscle contractions
✧ Modification of pain impulses
what is the order for the action potiental
- stimulus at -70 mV
- depolarization
3.repolarization - hyper polarization
- resting state
Remember the difference between Na+ and K+ ions moving inside and outside the cell- it creates a resting electrical charge of ______
-70 to -90 mV.
what is the resting level of the action potential
-70 to -90 mV
what does the action potential lead to
leads to depolarization. of the never
a stimulus requires adequate ___ and ___ in order to create an action potential and depolarization
intensity and duration
what is usually the site of depolarization
cathode (-)
what makes cells membrane more positive
anode
what are the 3 depolarization effects
- nerves impulse reached effector organ (nerve or mm) and impulse is transferred between motor end plate or synapses e
- NT is released
- mm contraction
what is the strength duration curve
a non linear relationship between current duration and current intensity
what is Rheobase
intensity of current necessary to cause OBSERVABLE tissue response given a longer duration
what is Chronaxie
duration required for a current of twice the intensity oh Rheobase to produce tissue excitation
A𝛃 what type of nerve is this and is it thick or thin
sensory and thick
A𝛅, what type of nerve is this
sharp pain
C, what kind of nerve is this
dull
A𝛃= sensory
C= dull pain
Denervated muscle
Motor
A𝛅= sharp pain
this these in order from thickest to thinnest
A𝛃= sensory
Motor
A𝛅= sharp pain
C= dull pain
Denervated muscle
Difference sizes and types of nerve fibers have different thresholds for depolarization… what is the order of never from least to most
AB
motor
Ad
and then C
nerves always depolarize in the same order… what is the order
• Sensory nerves
• Motor nerves
• Pain nerves
• Denervated muscle fibers
do large or small diameter nerves depolarize first ? what about superifical or deep nerves
large and superficial
what is the muscular response if there is a depolarization of motor nerve
mm contraction
T/F: In the absence of nerve innervation, a muscle can still contract by using electrical current to depolarize the muscle membrane
t
✧ Once a stimulus reaches a depolarizing threshold, nerve or muscle membrane depolarizes, and propagation of impulse occurs
✧ Stimulus causes depolarization or it does not. Reaction is the same regardless of the strength of the stimulus
that is this called
all or non response
what is a denervated mm
lost its peripheral nerve supply
a denervaeted mm …
✧___ in size
✧ ____ in tension generated with contraction
✧ ___ in time required for muscle contraction to occur
✧ Decrease in size
✧ Decrease in tension generated with contraction
✧ Increase in time required for muscle contraction to occur
what is the goal of electrical stimulation for a denervated mm
help minimize the extent of atrophy while nerve is regenerating
