electrical currents

Question 1

what is electrical flow?

Answer 1

the flow of charged particles

Question 2

what does an electrical circuit consist of?

Answer 2

-battery
-2 electrodes
-wires
-electrolytic solution

Question 3

where do positive ions flow towards?

Answer 3

the cathode

Question 4

where do negative ions flow toward?

Answer 4

• the anode

Question 5

what is voltage?

Answer 5

the difference in electrical potential between 2 points -it is the force that pushes electricity through wire

Question 6

what are the 3 steps of current?

Answer 6

-direct
-alternating
-pulsed

Question 7

what is a direct current?

Answer 7

-flow of electrons in one direction only
-rarely used now in electrotherapy
-higher risk of burn

Question 8

what are alternating current (AC)?

Answer 8

-continuous flow of charged particles in 2 directions

Question 9

what is a pulsed current?

Answer 9

an electrical current that is delivered through pulses
-most common current used in electrotherapy

Question 10

what are the types of pulsed currents?

Answer 10

-biphasic symmetrical PC
-biphasic assymmetrical PC

Question 11

what is he frequency / rate of currents?

Answer 11

-number of pulses or cycles delivered per unit time
-measured in pulses per second or Hz
-low freq eg TENS / NMES - 0-1000Hz

Question 12

what is a pulse duration?

Answer 12

the length of time the pulse lasts

Question 13

what is the peak amplitude of a current?

Answer 13

the maximum amplitude per phase

Question 14

what is the amplitude of the current?

Answer 14

-intensity or magnitude of current - milliamps
-this is what the patient feels

Question 15

what is the ramp time?

Answer 15

• the time taken for the amplitude to reach a peak

Question 16

what is ramp down time?

Answer 16

-the time taken for amplitude to return to 0

Question 17

define ohms law

Answer 17

voltage = current x resistance
V=IR

Question 18

what is the major resistance to current in electrotherapy and why does it vary?

Answer 18

the skin - acts as a capacitor
-skin resistance can vary due to thickness, moistness, blood supply

Question 19

define accommodation in physiology

Answer 19

-occurs during generation of AP
-refers to the rate of rise of a single electrical pulse in response to a stimulus
-if the rate is very flow, it will not provoke a nerve impulse

Question 20

what is adaption in physiology

Answer 20

an initial burst of impulses on stimulation and then the discharge rate falls greatly or may cease altogether
-occurs in most sensory types

Question 21

why is adaption important clinically?

Answer 21

the patient will feel a decrease in the intensity of the current after a few minutes

Question 22

what is a modulating current?

Answer 22

currents with sequential variations in the amplitude or pulse or frequency

Question 23

what does the order of nerve and muscle recruitment depend on?

Answer 23

type and size of nerve fibre

Question 24

what are the important nerve fibre types we need to know about in electrotherapy?

Answer 24

A alpha - motor to skeletal muscle
A beta- sensory touch and pressure
A gamma - motor to intramural fibres of muscle spindles
-A delta - sensory pain
C fibres - sensory pain

Question 25

what are general indications for use of electrical currents?

Answer 25

-pain control
-muscle stimulation
-iontophoresis-drug delivery
-enhance tissue healing

Question 26

what are electrodes used for in electrotherapy?

Answer 26

-used to conduct the current to the patients body