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138 Cards in this Set
- Front
- Back
Charge (coulombs) |
Loss or gain of electrons |
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Polarity: cathode (-), anode (+) |
Attraction/ repulsion forces = electric field -Alkaline reactions under the cathode softens underlying tissues |
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Attraction/repulsion forces |
Electric field |
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What do Alkaline reactions under the cathode do what to tissues? |
Softens |
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Voltage |
Driving force that moves electrons |
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Measure of potential energy |
Voltage |
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What are four main topics that define Principles of Electricity |
1. Charge 2. Polarity 3. Voltage 4. Conductors & insulators |
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Conductors are? |
- Water -Metals -nerves |
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Insulators are? |
-Rubber -Plastic -Fat |
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What are the 3 main properties of electrically excitable cell |
1. Resting Membrane Potential (RMP) 2. Action Potential 3. Propagation of Action Potential |
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What is the movement of the AP along the nerve called? |
Propagation |
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What is the cell membrane more permeable to vs what? |
Potassium (K +) & Negatively-charged proteins (anions) vs Sodium (Na+) |
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How is electrical potential generated across the cell membrane? |
Higher concentration of K+ & anions on the inside of the cell |
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What is higher on the outside of the cell. |
Na+ |
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Polarity means it has a? |
POLL Cathode (-) or Anode (+) |
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What happens within the cell & outside the cell when the positively charged K+ diffuse from the cell? |
Negative charge inside Positive charge outside |
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Anion has what type of charge? |
Negative |
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What type of charge does a Cation have? |
Positive |
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What is the RMP for excitable cells? |
-60 mV to -90 mV |
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How is RMP maintained by an active sodium potassium pump? |
Takes in K+ & extrudes Na+ |
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______ causes the cell membrane to become more permeable to Na+ ions. |
Stimulus (ex. electrical) |
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How is a Action Potential (AP) generated? |
Influx of Na+ causes a reduction in RMP -which occurs slowly at first. |
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Depolarization |
Reduction in the RMP |
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RMP stands for |
Resting membrane Postential |
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What is the critical threshold level? |
-55 mv |
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What happens when the transmembrane potential reaches a critical threshold level? |
The voltage-sensitive Na+ & K+ channels open widely |
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How does diffusion occur? How is this possible due to the fact Na+ is positive & K + is positive |
Large negative proteins [anions] inside the cell |
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Permeability to Na+ ______ & permeability to K+ _______ |
-Increases RAPIDLY -Increases SLOWLY |
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How is a flow of ions produced? |
Depolarization --> A positive charge is generated inside the cell & a negative charge outside |
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Transmembrane potential might rise as high as +35 mV during when? |
Depolarization |
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When are K+ channels fully opened? This causes what to happen? |
Na+ are closed -K+ rushes rapidly out of the cell--> Transmembrane Potential progressively becomes more negative |
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Repolarization |
When the transmembrane potential progressively more neg due to the K+ rushing out of the cell |
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Hyperpolarization |
K+ channels remain open long enough to repolarize the membrane (10-20 mV < RMP) |
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What happens at the end of the AP process? |
•K+ channels close & passive diffusion of the ions rapidly returns the RMP to its initial level. |
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How does RMP return to its initial level? |
K+ channels close & passive diffusion of the ions |
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How are successive depolarization in adjacent regions of the nerve, muscle, membranes triggered? |
Opening of the Na+ & K+ channels & voltage changes that produce an AP at one segment |
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What is the process called when a AP movement occurs along the surface of the nerve or muscle cell. |
Propagation of the AP |
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Amplitude means? |
How high you turn up the machine [current] |
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Duration what are two meanings |
-Duration of the electrical impulse itself -continuous or Pulse -TIME |
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Rate of rise |
-How fast the full strength comes on ex. turning the radio on in your car very fast (fast rate of rise) |
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Sequential Depolarization (eddy currents) generates what |
Movement of the AP along an unmyelinated nerve [slow] |
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What is the pace of conduction in a small diameter fibers & why? |
Slow: greater internal resistance in the small fibers -unmyelinated |
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Where does myelinated nerve fibers, saltatory conduction occur? |
Discrete junctures (Nodes of Ranvier) -in the myelin sheath which surrounds the nerve -Saltortatory conduction |
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AP is generated as ____ flow in at one location along an axon. [Step 2] |
Na+ |
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How is a AP initiated along a axon? |
Depolarization [Step 3] |
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How does repolarization occur? |
K+ ions flow out |
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Amplitude or Intensity of the stimulus must be great enough to cause the membrane potential to be lowered sufficiently to reach what? |
Threshold levels |
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Rheobase |
Minimum stimulation that will produce a minimum muscle contraction |
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Duration of the individual stimulus must be long to do what? |
Depolarize the cell membrane |
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Duration of Less than or equal to 1 ms does what to cells? |
Is sufficient to stimulate nerve cell membrane BUT TOO short to stimulate muscle cell membrane |
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Rate of rise of the current to the peal intensity must be _____ enough to prevent ______ |
-Rapid -Accommodation |
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Accommodation |
Rapid adjustment of the membrane to stimuli to prevent depolarization |
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What does square wave deliver?
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Instantaneous rise |
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Electro-diagnostic technique used to identify the state of injury of a motor nerve or muscle |
Strength-Duration Test |
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What two things have rendered strength-duration testing obsolete? |
1. Nerve conduction velocity 2. EMG |
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Pulse duration of the stimulus at twice the Rheobase intensity. |
Chronaxie |
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Intensity of current, having a long duration stimulus, required to produce minimum muscle contraction. |
Rheobase |
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What type of pulse with what type of intensity can depolarize sensory nerves? |
Short pulse duration ( 0.05 msec) with low intensities. low intensities |
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What represents the threshold for depolarization of a nerve fiber? |
Strength-Duration Curves |
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Muscle & nerve respond in a what type of fashion? |
All-or-none -no gradation of response |
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Shape of the curve relates what two things, necessary to cause the tissue to depolarize? |
1. Intensity of electrical stimulus (STRENGTH) 2. Length of time (DURATION) |
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Rheobase |
-minimum intensity of current necessary to cause tissue excitation when applied for a maximum duration |
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Chronaxie |
-Length of time (duration) required for current of twice the intensity of the rheobase current to produce tissue excitation |
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Name the type of fiber -Aß -A gamma -C |
-sensory & -motor -sensory - pain nerve fibers |
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The lower axis on strength-duration curves has what? |
Durations of several electrical simulators |
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Corresponding intensities would be necessary to create a _____? |
Depolarizing stimulus for any of the nerve fibers |
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What is a motor point? |
An area of greatest excitability on the skin surface in which a small amount of current generates a muscle response. |
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Where is the motor point located in a innervated muscle? |
At or near where the motor nerve enters the muscles, usually over the muscle belly |
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Where is the area of greatest excitability is located over where in DENERVATED muscle? |
Over the muscle, distally (insertion) area |
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A low frequency pulse (1-10 pulses/sec) produces what? |
-A brief muscle twitch or muscle contraction w/ each stimulus |
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How is a tetanic contractions occur? |
Increasing the number of stimuli (frequency) progressively fuses the individual muscle twitches to a point where the individual twitches are not discernible. |
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How is tetany caused? |
-Disease or other conditions that increase the AP frequency |
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AMPs |
rate of flow of electrons |
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Involuntary contraction of muscles caused by disease. |
Tetany |
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Blocking of the inhibition to the neurons that supply muscles, caused by disease tetanus is called what? |
Is called Muscle Cramps - not classified as tetany |
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Denervated Muscle contains what type of response |
Asynchronous or worm-like (vermicular) muscle - worm like movement |
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Movement of electrons through a conducting medium? |
Electrical Current |
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Rate of flow of electrons |
Amperage |
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Force that drives electrons through the conductive medium |
Voltage |
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Coulomb's Law |
Opposites Attract Likes Repel |
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Property of a medium which opposes the flow of electrons? |
Resistance |
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Ohm's Law expresses the relationship between what 3 things? |
1. Amperage 2. Voltage 3. Resistance |
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Conductance |
Inverse of resistance |
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Ohm's Law formula |
1. V= IR 2. I= V/R 3. R = V/I -V is sometimes E |
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What type of current was Ohm's law created? |
Direct current circuits |
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Define I- R- V- |
I- amps (intensity) R- resistance Ω V- Volts (sometimes E) |
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When resistance increases current _____? |
Decreases |
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Voltage current is defined as? |
Watts -aka (power) |
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Electron flow in amps is defined as? |
I: amps |
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Voltage difference between 2 circuits points? |
E (volts) |
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A circuit of 100 volts passes through a tissue w/ 5 ohmsof impedance. How many Amps of current are they? FORMULA |
Resistance = Volts x current (amps) V/ Ω = A Ω = V x A 100 V/5Ω = 20 A V --> somestimes E |
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100 volts & 5 ohms, how many amps of current are there? |
100 V/5Ω = 20 A |
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Current is equal to? |
Voltage divided by resistance A = V/R |
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Wattage |
is the total electrical power produced by the circuit & is equal to current times voltage W = A x V |
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Watt is ____ Watt = _____ X ______ |
Power Amp X Volt |
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Volt is _______ _________ Volt = ______ X _________ |
Current AMP X Ohm |
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Amp is _______ Amp = Volt / Ohm |
Current Volt X Ohm |
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Which is easier to measure Amps or watts? |
Measuring amps |
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Direct current |
Continuous unidirectional flow of electrons for at least 1 second |
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Words that describe Direct current |
-Interrupted -Reversed -Interrupted/reverse |
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Ampere (amp) |
a measure of the amount of electrically, called "current" in a circuit |
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Voltage is measure of what? |
Force behind that electricity's motion |
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Ohms is the resistance to? |
Current movement |
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Alternating current |
Uninterrupted bidirectional flow of electrons, --> must change direction at least once per second. |
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Pulse currents last how long? |
Less than 1 second |
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If a current last longer than one second? |
DIRECT |
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Pulsed current |
Unidirectional/ bidirectional flow of electrons that periodically ceases for short time period |
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(Symmetrical or asymmetrical), phase duration, peak amplitude, bursts ==> describe what? |
Monophasic/ Biphasic (pulse) |
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Words (currents) that describe Pulsed current 1. Duty cycle- Time modulation 2. Ramp time- Amplitude modulation 3. 4. |
3. Interphase/pulse intervals 4. Frequency (pps) |
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What are the two types of Physiological responses to Electrical current? |
1. Electrochemical effects 2. Electrothermal effects |
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Na+ to cathode (forms NaOH) Cl- to anode (forms HCl) -both combine with water |
Electrochemical effects |
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Heat is a product of kinetic energy of molecules secondary to friction and vibration |
Electrothermal effect |
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Electrochemical & Electrothermal effects are more concerned with what type of current? Why? |
Direct current -because tissue changes may occur -minimal concern w/ AC or pulsed current |
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What are more concerned w/ direct current |
Electrochemical & Electrothermal effects |
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Electrophysical effects: Depolarization of cells interrupt what? |
Resting concentration gradients |
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Electrophysical effects: ______ are depolarized 1st (-70 mV) then _____ (-90 mV) |
Nerves & Muscles |
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Sensory response |
the pt. is feeling the stimulation butyou cant see it |
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Motor Response |
when you can see it |
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Noxious response |
painful |
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Russian current |
Variation of AC used for strengthening muscles (aka Burst modulation) |
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High-volt pulsed current (HVPC) used for? |
-Pain modulation, tissue repair, wound healing |
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Interferential current is primarily used for? |
Pain Modulation |
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Low-intensity DC (microcurrent) used for? |
Tissue repair & wound healing |
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Symmetrical/ Asymmetrical Biphasic PC is used for what two things? |
Muscle stimulation & Pain modulation |
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What continues the AP propagation down the axon? |
Depolarization--Repolarization |
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How does propagation of AP specifically occur. Hint exchange of what ions? |
Na+ & K + ion & current flow is concentrated --> impulse jumps from Node to Node, conducting nerve impulses. |
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What type of pulse stimulates Motor nerves? |
Longer pulse durations (1 msec) |
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What type of pulse & intensity stimulates Denervated muscle? |
Longpulse durations (> 10msec) with high intensities |
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Example of a substance having HIGH resistance? Which is what? |
Rubber Insulator |
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Example of a substance having LOW resistance? Which is what? |
Metal Conductor |
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In Ohm's Law the current is _____ proportional to the voltage & ________ proportional to resistance. |
Directly & Inversely |
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What is a comprehensive measurement of power? |
Watts |
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Another term for quantity of current?
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Amps |
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What are the 3 levels of stimulation in order? |
1. Sensory 2. Motor 3. Noxious |
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What are the different High-Volt Pulsed Current? |
-Continuous -Reciprocating -Surge -Monophasic |
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What are the 2 different Interferential currents? |
1) Quadripolar 2) Bipolar |
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Low-intensity DC (microcurrent) does not stimulate what type of nerves? |
Sensory / Motor |
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What two types of therapeutic currents are similar with little to no difference in effectiveness for muscle stimulation. |
Symmetrical biphasic PC vs. Russian |