3 Muscle and Nerve Excitability

it is easier to start an action potential under a(n) _____.

cathode

an anode attracts _____ and forms ____.

a cathode attracts ____ and forms _____.

Cl-, HCl

Na+, NaOH

an acidic reaction results in ______.

sclerosis

“anode attracts acid”

a cathode reaction results in ______.

sclerolysis

energy that is lost in electrochemical exchange is converted to ____.

heat

the amount of energy lost in an electrochemical exchange is dependent on

amount of current flowing

resistance to current

duration

what is tissue impedance? what increases tissue impedance?

def: resistance of the tissue to the passage of electrical current flow

oily skin, lotion, makeup, body hair, calloused skin, dry skin, edema, ischemia, scarring, denervation

what tissue types have high and low impedance?

high: bone, fat, fascia

low: nerve, muscle (open wounds and abrasians)

what are the 2 components that can cause an action potential?

amplitude (strength) and duration (pulse length)

what is rheobase?

the minimum intensity capable of eliciting minimally detectable motor response

in mA

why would you need a double rheobase?

to account for skin resistance

what is chronaxie?

the minimum duration of an electric current needed to excite a nerve or muscle

the chronaxie of nerves < chronaxie of nerve fibers

T/F nerve fibers with the greatest diameter and highest resistance depolarize first.

F, nerve fibers with the greatest diameter and lowest resistance depolarize first

what nerve fiber types would depolarize first? (list from most to least)

A-alpha: proprioception, motor

A-beta: touch, pressure

A-delta: pain, temperature

C: pain

fibers (closest/farthest) to the electrode will be exicited first.

closest

this is why you feel a-beta e-stim before you see a motor response

how to target deeper fibers?

increase intensity or pulse duration

what is the order of the level of response to e-stim?

1. sensory

2. motor

3. noxious