Concepts of Therapeutic Electric Current

Question 1

Types of kinetic energy

Answer 1

• thermal (energy of moving particles-heat)
• mechanical (energy of objects in motion)
• electrical (energy of particles moving though a wire)
• magnetic (energy causing push or pull)

Question 2

Types of potential energy

Answer 2

• chemical (energy stored in food or fuel)
• elastic (energy stored in objects that are stretched)
• nuclear (energy stored in center of particles)
• gravitational (energy stored in an object when it’s above earth’s surface)

Question 3

Ways energy is transferred

Answer 3

conduction = transfer through direct contact (touching a hot pot)

convection = transfer through liquid or gas from the movement of the particles (oven, boiling water)

conversion = change of energy from one state to another (water or wind to electricity)

Question 4

Electric charge

Answer 4

physical property of matter that causes it to experience of force when placed in an electric field

Question 5

How is electric charge carried out?

Answer 5

subatomic particles which determine electromagnetic interaction

Question 6

What is the source of the electromagnetic force?

Answer 6

the interaction between a moving charge and an electromagnetic field

Question 7

Electricity

Answer 7

type of energy that can build up in one place or flow from one place to another

Question 8

Static electricity

Answer 8

when electricity gathers in one place
- potential energy
ex: a battery

Question 8

Current electricity

Answer 8

electricity that moves from one place to another
- kinetic energy

Question 9

How is electricity “made”?

Answer 9

caused by electrons that orbit around atoms
- electrons have a NEGATIVE charge

Question 10

Why is there no charge in atoms?

Answer 10

they have equal amounts of protons and electrons (positive and negative charges)

Question 11

Why do electricity flow easily through metal but not rubber?

Answer 11

• metals have “free” electrons that are not bound tightly to the parent atoms which enables electric current flow
• rubber has more “bound” electrons which prevents flow of the electric current

Question 12

Predictable behaviors of charges:

Answer 12

• opposite charges attract
• like charges repel
• charges can’t be created or destroyed
• charges can be transferred from object to object

Question 13

Cation

Answer 13

atom losses electrons in its outer shells without changing the number of protons it has in its nucleus
- POSITIVE charge

Question 14

Anion

Answer 14

atom gains electrons in its outer shell
- NEGATIVE charge

Question 15

Ions

Answer 15

atom with either an excess or deficiency of electrons

Question 16

Coulombs law

Answer 16

• force created by 2 particles is equal to the strength and charge
• force created by 2 particles is inversely proportional to the distance

Question 17

Electrical potential difference

Answer 17

potential energy that is converted to kinetic energy when particles are approximated

Question 18

Electromotive force (EMF)/Voltage

Answer 18

movement of particles

Question 19

Current

Answer 19

movement of charged particles through a conductor in response to an applied electrical field of voltage

Question 20

What is responsible for the physiological changes during electrical stimulation?

Answer 20

current, the transfer of energy from one point to another

Question 21

What do you need to have a current?

Answer 21

• driving force to move the particles (current generator)
• conductive pathway (wires, electrodes, excitatory cells)
• difference in electrical potential (generator to body)

Question 22

Why does current flow from generator to body?

Answer 22

the body has a lower electrical potential than the generator

Question 23

OHM’s law

Answer 23

current (I) = voltage (V) / resistance (R)

magnitude of current in a conductor is INVERSELY PROPORTIONAL to resistance and PROPORTIONAL to voltage

Question 24

Constant voltage stimulators

Answer 24

don't adjust voltage in response to impedance

Question 25

Resistance

Answer 25

the opposition to direct current flow through a conductor in a circuit

Question 26

Series circuit

Answer 26

- component resistors are side by side w/ ends connected (one pathway) - flow is inversely proportional to resistance - total voltage is sum of all the voltages at each component

Question 27

Parallel circuit

Answer 27

- component resistors create multiple pathways - flow depends on resistance - total voltage is the same of voltage at each component

Question 28

What happens with a greater impedance of the skin?

Answer 28

the voltage of the electrical current needs to be higher - chemical changes in the skin make it more resistant to certain types of current

Question 29

Capacitance

Answer 29

ability of the conductor or insulator to store electrical charge before an action potential occurs

Question 30

What does a time constant describe in cell membranes?

Answer 30

each excitable cell membrane has a time constant that describes the rise and decay of electrical potentials

Question 31

Time constant

Answer 31

the product of the membrane's resistance and capacitance

Question 32

What does a time constant do?

Answer 32

determines the MIN duration that a stimulus must exist before the cell's threshold for depolarization is reached

Question 33

Impedence

Answer 33

opposition to alternating current - sum of resistive, capacitive, and inductive components of the tissue (impair current flow) - PARTIALLY affected by the frequency of the applied electrical current - INVERSELY proportional to the applied frequency

Question 33

What is the normal resting membrane potential of a peripheral nerve?

Answer 33

-70mV created by the difference between the inside of the cell membrane (NEGATIVE) and the outside of the cell membrane

Question 34

Muscle and nerve membrane ions:

Answer 34

Na+ is higher outside K+ is higher inside each ion will want to move across the membrane to equal out the concentration

Question 35

Leak channels

Answer 35

membranes are more permeable to K+ so more K+ will move out of the cell - creates a net negative charge inside cell - loss of K+ will stop as the cell becomes more negative and will require a positive charge to move back into cell

Question 36

Action potentials

Answer 36

if a stimulus is introduced, the cell membrane can change its permeability to Na+ - Na+ moves into cell to reduce negative charge inside - increase in positive charges inside will hit a threshold and a thrust of Na+ will enter (DEPOLARIZATION)

Question 37

When will depolarization occur?

Answer 37

at -55mV

Question 38

Initial activity increased permeability to K+ to cause?

Answer 38

the membrane to become more negative (HYPERPOLARIZATION) - happens after Na+ change

Question 39

Excitable cell

Answer 39

a cell that has the ability to generative an action potential

Question 40

What is threshold determined by?

Answer 40

- amplitude which will vary from membrane to membrane - duration of the stimulus

Question 41

Absolute refractory period

Answer 41

membrane needs 1-2 msec to recover excitability after an action potential

Question 42

Relative refractory period

Answer 42

membranes needs .5-1 msec to recover excitability after an action potential of a higher stimulus