Electrical Stimulation Part 1

Question 1

Charge:

Answer 1

loss or gain of electrons, measured in coulombs

Question 2

Polarity:

Answer 2

cathode (-) anode (+) Attraction/repulsion forces = electric field. Alkaline reactions under the cathode softens underlying tissues.

Question 3

The medication is (+) what charge should the machine be to drive the medication into the body

Answer 3

(+); like polarities repel each other

Question 4

Voltage:

Answer 4

driving force that moves electrons, a measure of potential energy

Question 5

Conductor examples:

Answer 5

water, metal, nerves; anything that helps the electrons along their way

Question 6

Insulator examples:

Answer 6

rubber, plastic, fat; anything that inhibits the transmission

Question 7

Properties of electrically excitable cell

Answer 7

resting membrane potential (RMP) -70mv usually, Action Potential, Propagation of an Action Potential (movement of the action potential along the nerve)

Question 8

The cell membrane is more permeable to _____ in comparison with _____________ and negatively-charged proteins (anions).

Answer 8

potassium (K+), sodium (Na+)

Question 9

An electrical potential is generated across the cell membrane due to the higher concentrations of K+ and anions on the ____ of the cell relative to the concentration of Na+ on the ____

Answer 9

inside, outside

Question 10

A ____ charge is produced within the cell and a positive charge develops on the outside of the cell as the ____ charged K+ diffuses from the cell

Answer 10

negative, positive

Question 11

RMP is ____mV to ____mV for excitable cells

Answer 11

-60, -90

Question 12

RMP is maintained by:

Answer 12

an active sodium potassium pump that takes in K+ and extrudes Na+

Question 13

A stimulus causes the cell membrane to become more ____ to ___ ions

Answer 13

permeable, Na+

Question 14

An action potential is generated when the influx of ____ causes a reduction of RMP which occurs slowly at first. Reduction in the RMP is called _____.

Answer 14

Na+, depolarization

Question 15

When transmembrane potential reaches a critical threshold level (approximately ____mV), the voltage-sensitive Na+ and K+ channels ___.

Answer 15

-55, open widely

Question 16

Permeability to Na+ increases _____, whereas the permeability to K+ increases _____.

Answer 16

rapidly, slowly

Question 17

During depolarization, transmembrane potential might rise as high as ____mV. A positive charge is generated inside the cell and a negative charge outside is produced, as a result of the flow of ions.

Answer 17

+35

Question 18

The ___ channels are fully open about the time the ___ are closed and ___rushes rapidly out of the cell, making the transmembrane potential progressively more negative. This process is repolarization.

Answer 18

K+, Na+, K+

Question 19

The ____ channels remain open long enough to repolarize the membrane (_________mv <RMP). This is called hyperpolarization.

Answer 19

K+, 10-20

Question 20

The ____ channels close and passive diffusion of the ions ____ returns the RMP to its initial level.

Answer 20

K+, rapidly

Question 21

Opening of the Na+ and K+ channels and voltage changes that produce a AP at one segment of the membrane triggers successive depolarization in adjacent regions of the ____, _____, or ____

Answer 21

nerve, muscle, membrane

Question 22

AP movement occurs along the ____ of the nerve or muscle cell

Answer 22

surface

Question 23

Movement of the AP along an unmyelinated nerve is generated via sequential depolarization (____) along neighboring sites in the nerve membrane.

Answer 23

eddy currents

Question 24

Speed of conduction in ____ diameter fibers is ____ because of the greater internal resistance in the small fibers.

Answer 24

small, slow

Question 25

In myelinated nerve fibers, ______ conduction occurs at discrete junctures (_______) in the myelin sheath which surrounds the nerve

Answer 25

salutatory, nodes of Ranvier

Question 26

What is the sequence of nerve conduction

Answer 26

1. Conduction of an action potential. An action potential is generated as Na+ ions flow in at one location along an axon. 2. The depolarization spreads to the neighboring region of the membrane, initiating an action potential there. 3. The original region repolarized as K+ ions flow out. 4. The depolarization-repolarization process is repeated as the action potential is propagated down the axon.

Question 27

Na+ and K+ ion exchange and current flow. The impulse jumps from node to node, conducting nerve impulses at greater rates compared to _____, unmylinated nerve fibers.

Answer 27

smaller

Question 28

In order to cause the membrane potential to be lowered sufficiently to reach threshold levels the _____ or ____ of the stimulus must be great enough.

Answer 28

amplitude, intensity

Question 29

Duration of the individual stimulus must be long enouh to produce depolarization of the cell membrane. A duration of less than or equal to ___ms is sufficient to stimulate nerve cell membrane, but is too short to stimulate muscle cell membrane.

Answer 29

1

Question 30

Rate of rise of the current to the peak intensity must be ____ enough to prevent accommodation, which is the ____ adjustment of the membrane to stimuli to prevent depolarization.

Answer 30

rapid, rapid

Question 31

____ wave delivers instantaneous rise

Answer 31

square

Question 32

Rheobase:

Answer 32

intensity of the current, having a long duration stimulus, required to produce a minimum muscle contraction

Question 33

Chronaxie:

Answer 33

the pulse duration of the stimulus at twice the rheobase intensity. Chronaxie of a denervated muscle is >1 msec

Question 34

What pulse duration can depolarize sensory nerves

Answer 34

very short pulse durations <0.05msec

Question 35

What pulse duration can depolarize motor nerves

Answer 35

longer pulse durations <1 msec

Question 36

What pulse duration is required to elicit a response from a denervated muscle

Answer 36

long pulse duration >10 msec with high intensities

Question 37

Nerve conduction velocity and EMG have rendered __________________ virtually obsolete

Answer 37

strength-duration testing

Question 38

motor point:

Answer 38

an area of greatest excitability on the skin surface in which a small amount of current generates a muscle response

Question 39

In innervated muscle, the motor point is located ___ or ___ where the motor nerve enters the muscle, usually over the ___________.

Answer 39

at, near, muscle belly

Question 40

In denervated muscle, the area of greatest excitability is located _____ the muscle _____toward the insertion

Answer 40

over, distally

Question 41

A brief muscle twitch or muscle contraction requires a ______ with each stimulus

Answer 41

low frequency pulse (1-10 pulses/sec)

Question 42

Fusing the number of individual muscle twitches to a point where the individual twitches are not discernible results in a _______; increasing the number of stimuli (frequency) progressively.

Answer 42

tetanic contraction

Question 43

Tetany:

Answer 43

the involuntary contraction of muscles, which may be caused by disease or other conditions that increase the action potential frequency

Question 44

Muscle cramps that are caused by the disease tetanus are not classified as tetany; rather, they are due to:

Answer 44

a blocking of the inhibition to the neurons that supply muscles

Question 45

Denervated muscle produces a ____ response

Answer 45

asynchronous or worm-like (vermicular)

Question 46

Electrical current:

Answer 46

the movement of electrons through a conducting medium

Question 47

voltage:

Answer 47

the force that drives electrons through the conductive medium

Question 48

Resistance:

Answer 48

is the property of a medium which opposes the flow of electrons. A substance having a high resistance (e.g., rubber) is an insulator and a substance having a low resistance (e.g., metal) is a conductor

Question 49

Ohm' law expresses the relationship between ____, ____, and _____.

Answer 49

amperage, voltage, resistance

Question 50

The current is directly proportional to the ____ and inversely proportional to the ____.

Answer 50

voltage, resistance

Question 51

The inverse of resistance is called ____

Answer 51

conductance

Question 52

What is Ohm's Law equation:

Answer 52

I(amps) = V(volts) / R(resistance)

Question 53

When resistance increases, current _____

Answer 53

decreases

Question 54

edema control:

Answer 54

high volt

Question 55

A circuit of 100 volts passes through a tissue with 5 ohms of impedance. How many amps of current are there?

Answer 55

100 V/5 ohms = 20A

Question 56

Alternating current:

Answer 56

uninterrupted bidirectional flow of electrons, must change direction at least once per second

Question 57

Pulsed current:

Answer 57

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

Question 58

Electrochemical effects:

Answer 58

Na+ to cathode (forms NaOH), Cl- to anode (forms HCl) -- both combine with water

Question 59

Electrothermal effects

Answer 59

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

Question 60

Tissue changes may occur with __; minimal concern with __ or pulsed current

Answer 60

DC, AC

Question 61

What is depolarized first nerves or muscles? At what mV?

Answer 61

nerves are depolarized first (-70mV), then muscles (-90mV)

Question 62

Levels of stimulation can be ___, ___, and ____

Answer 62

sensory, motor, noxious

Question 63

Russian current (burst modulation):

Answer 63

variation of AC used for strengthening muscles

Question 64

What is High-Volt Pulsed Current (HVPC)? What is it used for?

Answer 64

continuous, reciprocating, or surge (monophasic). Used for pain modulation, tissue repair, wound healing.

Question 65

What is Interferential Current (IFC)? What is it used for?

Answer 65

Quadripolar or bipolar set-ups available on most devices. Used primarily for pain modulation.

Question 66

What is low-intensity DC (microcurrent)? What is it used for?

Answer 66

It does not stimulate sensory/motor nerves. Used for tissue repair, wound healing

Question 67

What is symmetrical/asymmetrical biphasic PC?

Answer 67

Used for muscle stimulation & pain modulation. Little to no difference in effectiveness for muscle stimulation using symmetrical biphasic PC vs. Russian.