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138 Cards in this Set

  • Front
  • Back

Charge (coulombs)

Loss or gain of electrons

Polarity: cathode (-), anode (+)

Attraction/ repulsion forces = electric field

-Alkaline reactions under the cathode softens underlying tissues

Attraction/repulsion forces

Electric field

What do Alkaline reactions under the cathode do what to tissues?



Driving force that moves electrons

Measure of potential energy


What are four main topics that define Principles of Electricity

1. Charge

2. Polarity

3. Voltage

4. Conductors & insulators

Conductors are?

- Water



Insulators are?




What are the 3 main properties of electrically excitable cell

1. Resting Membrane Potential (RMP)

2. Action Potential

3. Propagation of Action Potential

What is the movement of the AP along the nerve called?


What is the cell membrane more permeable to vs what?

Potassium (K +) & Negatively-charged proteins (anions)


Sodium (Na+)

How is electrical potential generated across the cell membrane?

Higher concentration of K+ & anions on the inside of the cell

What is higher on the outside of the cell.


Polarity means it has a?


Cathode (-) or Anode (+)

What happens within the cell & outside the cell when the positively charged K+ diffuse from the cell?

Negative charge inside

Positive charge outside

Anion has what type of charge?


What type of charge does a Cation have?


What is the RMP for excitable cells?

-60 mV to -90 mV

How is RMP maintained by an active sodium potassium pump?

Takes in K+ & extrudes Na+

______ causes the cell membrane to become more permeable to Na+ ions.

Stimulus (ex. electrical)

How is a Action Potential (AP) generated?

Influx of Na+ causes a reduction in RMP

-which occurs slowly at first.


Reduction in the RMP

RMP stands for

Resting membrane Postential

What is the critical threshold level?

-55 mv

What happens when the transmembrane potential reaches a critical threshold level?

The voltage-sensitive Na+ & K+ channels open widely

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

Permeability to Na+ ______ & permeability to K+ _______

-Increases RAPIDLY

-Increases SLOWLY

How is a flow of ions produced?

Depolarization --> A positive charge is generated inside the cell & a negative charge outside

Transmembrane potential might rise as high as +35 mV during when?


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


When the transmembrane potential progressively more neg due to the K+ rushing out of the cell


K+ channels remain open long enough to repolarize the membrane (10-20 mV < RMP)

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.

How does RMP return to its initial level?

K+ channels close & passive diffusion of the ions

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

What is the process called when a AP movement occurs along the surface of the nerve or muscle cell.

Propagation of the AP

Amplitude means?

How high you turn up the machine [current]

Duration what are two meanings

-Duration of the electrical impulse itself

-continuous or Pulse


Rate of rise

-How fast the full strength comes on

ex. turning the radio on in your car very fast (fast rate of rise)

Sequential Depolarization (eddy currents) generates what

Movement of the AP along an unmyelinated nerve [slow]

What is the pace of conduction in a small diameter fibers & why?

Slow: greater internal resistance in the small fibers


Where does myelinated nerve fibers, saltatory conduction occur?

Discrete junctures (Nodes of Ranvier)

-in the myelin sheath which surrounds the nerve

-Saltortatory conduction

AP is generated as ____ flow in at one location along an axon. [Step 2]


How is a AP initiated along a axon?


[Step 3]

How does repolarization occur?

K+ ions flow out

Amplitude or Intensity of the stimulus must be great enough to cause the membrane potential to be lowered sufficiently to reach what?

Threshold levels


Minimum stimulation that will produce a minimum muscle contraction

Duration of the individual stimulus must be long to do what?

Depolarize the cell membrane

Duration of Less than or equal to 1 ms does what to cells?

Is sufficient to stimulate nerve cell membrane


TOO short to stimulate muscle cell membrane

Rate of rise of the current to the peal intensity must be _____ enough to prevent ______




Rapid adjustment of the membrane to stimuli to prevent depolarization

What does square wave deliver?

Instantaneous rise

Electro-diagnostic technique used to identify the state of injury of a motor nerve or muscle

Strength-Duration Test

What two things have rendered strength-duration testing obsolete?

1. Nerve conduction velocity

2. EMG

Pulse duration of the stimulus at twice the Rheobase intensity.


Intensity of current, having a long duration stimulus, required to produce minimum muscle contraction.


What type of pulse with what type of intensity can depolarize sensory nerves?

Short pulse duration ( 0.05 msec) with low intensities.

low intensities

What represents the threshold for depolarization of a nerve fiber?

Strength-Duration Curves

Muscle & nerve respond in a what type of fashion?


-no gradation of response

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)


-minimum intensity of current necessary to cause tissue excitation when applied for a maximum duration


-Length of time (duration) required for current of twice the intensity of the rheobase current to produce tissue excitation

Name the type of fiber


-A gamma


-sensory & -motor


- pain nerve fibers

The lower axis on strength-duration curves has what?

Durations of several electrical simulators

Corresponding intensities would be necessary to create a _____?

Depolarizing stimulus for any of the nerve fibers

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.

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

Where is the area of greatest excitability is located over where in DENERVATED muscle?

Over the muscle, distally (insertion) area

A low frequency pulse (1-10 pulses/sec) produces what?

-A brief muscle twitch or muscle contraction w/ each stimulus

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.

How is tetany caused?

-Disease or other conditions that increase the AP frequency


rate of flow of electrons

Involuntary contraction of muscles caused by disease.


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

Denervated Muscle contains what type of response

Asynchronous or worm-like (vermicular) muscle

- worm like movement

Movement of electrons through a conducting medium?

Electrical Current

Rate of flow of electrons


Force that drives electrons through the conductive medium


Coulomb's Law

Opposites Attract

Likes Repel

Property of a medium which opposes the flow of electrons?


Ohm's Law expresses the relationship between what 3 things?

1. Amperage

2. Voltage

3. Resistance


Inverse of resistance

Ohm's Law formula

1. V= IR

2. I= V/R

3. R = V/I

-V is sometimes E

What type of current was Ohm's law created?

Direct current circuits





I- amps (intensity)

R- resistance Ω

V- Volts (sometimes E)

When resistance increases current _____?


Voltage current is defined as?


-aka (power)

Electron flow in amps is defined as?

I: amps

Voltage difference between 2 circuits points?

E (volts)

A circuit of 100 volts passes through a tissue w/ 5 ohmsof impedance.

How many Amps of current are they?


Resistance = Volts x current (amps)

V/ Ω = A

Ω = V x A

100 V/5Ω = 20 A

V --> somestimes E

100 volts & 5 ohms, how many amps of current are there?

100 V/5Ω = 20 A

Current is equal to?

Voltage divided by resistance

A = V/R


is the total electrical power produced by the circuit & is equal to current times voltage

W = A x V

Watt is ____

Watt = _____ X ______


Amp X Volt

Volt is _______ _________

Volt = ______ X _________



Amp is _______

Amp = Volt / Ohm


Volt X Ohm

Which is easier to measure Amps or watts?

Measuring amps

Direct current

Continuous unidirectional flow of electrons for at least 1 second

Words that describe Direct current




Ampere (amp)

a measure of the amount of electrically, called "current" in a circuit

Voltage is measure of what?

Force behind that electricity's motion

Ohms is the resistance to?

Current movement

Alternating current

Uninterrupted bidirectional flow of electrons, --> must change direction at least once per second.

Pulse currents last how long?

Less than 1 second

If a current last longer than one second?


Pulsed current

Unidirectional/ bidirectional flow of electrons that periodically ceases for short time period

(Symmetrical or asymmetrical), phase duration, peak amplitude, bursts ==> describe what?

Monophasic/ Biphasic (pulse)

Words (currents) that describe Pulsed current

1. Duty cycle- Time modulation

2. Ramp time- Amplitude modulation



3. Interphase/pulse intervals

4. Frequency (pps)

What are the two types of Physiological responses to Electrical current?

1. Electrochemical effects

2. Electrothermal effects

Na+ to cathode (forms NaOH)

Cl- to anode (forms HCl)

-both combine with water

Electrochemical effects

Heat is a product of kinetic energy of molecules secondary to friction and vibration

Electrothermal effect

Electrochemical & Electrothermal effects are more concerned with what type of current?


Direct current

-because tissue changes may occur

-minimal concern w/ AC or pulsed current

What are more concerned w/ direct current

Electrochemical & Electrothermal effects

Electrophysical effects: Depolarization of cells interrupt what?

Resting concentration gradients

Electrophysical effects: ______ are depolarized 1st (-70 mV) then _____ (-90 mV)

Nerves & Muscles

Sensory response

the pt. is feeling the stimulation butyou cant see it

Motor Response

when you can see it

Noxious response


Russian current

Variation of AC used for strengthening muscles

(aka Burst modulation)

High-volt pulsed current (HVPC) used for?

-Pain modulation, tissue repair, wound healing

Interferential current is primarily used for?

Pain Modulation

Low-intensity DC (microcurrent) used for?

Tissue repair & wound healing

Symmetrical/ Asymmetrical Biphasic PC is used for what two things?

Muscle stimulation & Pain modulation

What continues the AP propagation down the axon?


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.

What type of pulse stimulates Motor nerves?

Longer pulse durations (1 msec)

What type of pulse & intensity stimulates Denervated muscle?

Longpulse durations (> 10msec) with high intensities

Example of a substance having HIGH resistance?

Which is what?



Example of a substance having LOW resistance? Which is what?



In Ohm's Law the current is _____ proportional to the voltage & ________ proportional to resistance.

Directly & Inversely

What is a comprehensive measurement of power?


Another term for quantity of current?


What are the 3 levels of stimulation in order?

1. Sensory

2. Motor

3. Noxious

What are the different High-Volt Pulsed Current?





What are the 2 different Interferential currents?

1) Quadripolar

2) Bipolar

Low-intensity DC (microcurrent) does not stimulate what type of nerves?

Sensory / Motor

What two types of therapeutic currents are similar with little to no difference in effectiveness for muscle stimulation.

Symmetrical biphasic PC vs. Russian