Physiology of Electrical Stimulation & ES Application for Pain

Question 1

artificial area of depolarization

Answer 1

an electrode placed in the periphery bypasses the CNS to stimulate muscle

Question 2

orthodromic

Answer 2

traveling in the normal direction in a nerve fiber.

activate nerves and muscles

Question 3

Antidromic

Answer 3

traveling in the opposite direction to that normal in a nerve fiber

pain relief

Question 4

force generation via ES: volitional contraction

Answer 4

small diameter alpha motor neurons recruited first, then larger ones as more force is needed

Question 5

rate coding

Answer 5

increase tension

-CNS increases firing rate of motor units contracting

Question 6

Asynchronous

Answer 6

swapping motor units in & out to reduce fatigue

Question 7

Natural recruitment order

Answer 7

slow twitch type 1

• -> fast twitch , fatigue resistant, type IIA
• -> fast twitch fatiqguable type II B

Question 8

force generation via ES: Stimulated Contraction

Answer 8

larger diameter alpha motor neurons recruited first and then smaller ones last

Question 9

which type of muscles are recruited first in stimulated contraction

Answer 9

fatigable

Question 10

recruitment order for stimulated contraction

Answer 10

fast twitch, fatigable type IIB

–> fast twitch, fatigue resistance, type IIA

–> slow twitch type I

Question 11

factors influencing muscle force production via ES

Answer 11

• frequency of activation
• amplitude of activation
• pulse duration

Question 12

Frequency

Answer 12

increases firing rate, force, & increases fatigue

Question 13

Twitch

Answer 13

initial pulse creates AP

Question 14

Unfuse tetany

Answer 14

another pulse occurs before Ca+ reuptake occurs

oscillations (3-20 pps)

Question 15

Fused Tetany

Answer 15

summative effect

greater than 20 pps

Question 16

critical fusion frequency

Answer 16

can differ among muscles

Question 17

amplitude

Answer 17

stimulated deeper and smaller fibers

increases force production

Question 18

pulse duration

Answer 18

stimulate smaller fibers
increases force production

pain over 400 usec

Question 19

clinical respones

Answer 19

sensory
motor
noxious

Question 20

sensory

Answer 20

first response as stim is turned on “tingling”

Question 21

motor

Answer 21

alpha motor neurons threshold is reached

-recruitment increases as stim increases

Question 22

noxious

Answer 22

pain fibers are being stimulated

PD> 400 u sec activates all fibers

Question 23

motor point

Answer 23

the point on skin which smallest amount of current activates the muscle

located near the point that peripheral nerve enters muscles

Question 24

innervated muscle

Answer 24

muscle has intact peripheral nerve

Question 25

denervated muscle

Answer 25

peripheral nerve is damaged

Question 26

denervated & fibrotic

Answer 26

nerve is damaged plus muscle has undergone changes preventing contraction

Question 27

anode (+) effects

Answer 27

- acid produces - coagulates protein - hardens tissue - accelerates tissue growth

Question 28

cathode (-) effects

Answer 28

- base produces - liquifies protein - softens tissue - bacteriostatic effect (get rid of ecoli)

Question 29

current density

Answer 29

size of the electrode influences the excitability of the tissue under it (charge delivered over the area of the electrode)

Question 30

ES for pain control relies upon two mechanism

Answer 30

Gate-theory (short lasting) Central mechanisms (long lasting)

Question 31

First order neurons

Answer 31

A-beta A-delta C afferents

Question 32

A-betta (II)

Answer 32

joint, touch, muscle spindle receptors

Question 33

A-delta (III)

Answer 33

free ending | fast pain

Question 34

C afferents (IV)

Answer 34

free ending | slow pain

Question 35

substantia gelatinosa

Answer 35

- act as a modulator - when active, there is a decrease in sensory input to the 2nd order neuron -A-beta first activate the 2nd order and then decrease through SG

Question 36

Inhibitory interneuron

Answer 36

A-delta and C's activate the 2nd order neurons -also activate an inhibitory interneuron which inhibits the SG, causing increased activity

Question 37

Pre-synpatic inhibition of 2nd order neuron

Answer 37

the SC acts pre-synaptically to alter the signal to the 2nd order neurons that affects the pain signals sent to higher centers for perception WDR

Question 38

central mechanism : 2nd order neurons to higher centers 1st path

Answer 38

axons 1 & V cross midline to ascend uninterrupted via the lateral spinothalamic tract which ascends on the contralateral side of the spinal cord

Question 39

central mechanism : 2nd order neurons to higher centers 2nd path

Answer 39

spino-reticulo-thalamic tract requires multiple synapses as pain information ascends

Question 40

medulla and pons are responsible for

Answer 40

autonomic responses to intense noxious stimuli important in the affective components of pain

Question 41

Thalamus

Answer 41

- recognition of location and type of pain occurs here - initiating the behavioral reactions to pain - sends projections to the cortex

Question 42

endorphins

Answer 42

endogenous morphine

Question 43

Endogenous Opioid System

Answer 43

Beta-endorphins are released by the pituitary and can have long lasting effect on pain (6-8 hours)

Question 44

The medulla and pons role in Endogenous Opioid System

Answer 44

release neurotransmitters that are either inhibitory or excitatory on the SG

Question 45

medulla

Answer 45

serotonin - inhibitory

Question 46

pons

Answer 46

norepinephrine exciting

Question 47

Counter Irritation Analgesia

Answer 47

idea that acute painful stimulus can alleviate ongoing pain (acupunture ) works on endorphin system

Question 48

Contraindications

Answer 48

``` Implanted Devices Carotid Sinus Damaged Skin Reproductive Organs Transcranial application Eyes Cancer Pregnancy Epilepsy Thrombosis Hemorrhage Radiated tissues Infection/Tuberculosis ```

Question 49

Pre-Cautions

Answer 49

``` Undiagnosed pain Cancer Pregnancy Cognitive Impairment Cardiovascular disease Extreme edema Extreme adipose Adverse TENS experience Visual impairment Trans thoracic applications Impaired sensation/scar tissue ```