Principles of Electricity Flashcards
1
Q
electricity
A
a fundamental form of energy observable in positive and negative forms that occurs naturally or is produced
2
Q
types of electricity
A
- static: friction between two objects, one gains electrons and one loses electrons
3
Q
current electricity
A
- current flow: movement of electrons, bees to a hive
- volts and amps (intensity)
- electrons flow through a circuit
- conductors: allow the current to pass through
- insulators: block the current flow
- resistors: let some flow through, slow flow down (ohms)
- watt: the amour of work that is done as amps are pushed by volts
4
Q
voltage (V)
A
- amount of electrical pressure
- the potential to cause current: the potential to cause something electrical to happen
- 12V car battery has 12V of potential
- a 120V wall outlet has potential, but nothing happens unless you plug something in and turn it on
5
Q
amperage (A)
A
- volume of electricity that flows past a particular point in a given period of time
6
Q
electrical current (I)
A
- the rate as which charge flows through a cross section of a conductor in a unit time
- quantity of charge (coulomb/time)
- on an e-stem unit, when you turn the knob that increases the intensity of the current, you are increasing the amps
7
Q
volt
A
- a uit of force required to push a current of 1 amp (A) through the resistance of 1 ohm
- volts, ot voltage, can come from batteries or a generator
8
Q
Ohm’s law
A
- a relationship between current, voltage, and resistance
- current is directly proportional to voltage and inversely proportional to resistance
- V=IR
9
Q
closed circuit
A
- a closed circuit is formed when a complete path is formed between two poles
- positive pole= anode
- negative pole= cathode
10
Q
non-biologic insulators
A
- glass, rubber, oil, asphalt, fiberglass, porcelain, ceramic, quartz, dry cotton, dry paper, dry wood, plastic, air, diamond
11
Q
non-biologic conductors
A
- silver, copper, gold, aluminum, iron, steel, brass, bronze, mercury, graphite, dirty water, concrete
12
Q
biologic tissues
A
- blood and nerves: high electron flow= low electrical impedance (easiest for it to pass through)
- muscle: medium electron flow, medium impedance
- skin, adipose tissue, and bone: low electron flow, high impedance
13
Q
lowering impedance for electrode application
A
- clean skin with alcohol
- ask athlete to avoid use of lotion
- electrodes should be lubricated
- limit hair under electrode
14
Q
Other factors determining impedance
A
length of circuit
- the shorter the distance that an electron has to travel, the less resistance to current flow
- want it to be closer together
the resistance of an electrical circuit path is inversely proportional to its cross sectional diameter
- greater cross sectional area of a path, the less resistance to current flow
increasing temp of tissue
- decreases the resistance to current flow.
15
Q
types of electrical stimulation currents:
Direct current
A
- direct currents (galvanic current): uninterrupted flow of electrons, either completely above or below line
- electrons travel cathode to anode
- properties of electrical flow: amplitude: maximum distance, pulse duration: horizontal distance, pulse charge: area within the waveform
- used to produce local polarity-based changes in human tissue
- iontophoresis
16
Q
types of electrical stimulation currents:
Alternating current
A
- direction of current flow changes from positive to negative in a cyclical manner (no true positive or negative pole)
- basic pattern is a sine wave
- amplitude: peak to peak
- frequency: cycles per second (Hz)
- cycle duration: inversely related to frequency
17
Q
types of electrical stimulation currents:
Pulsed currents
A
- monophasic current: unidirectional flow of electrons. pulses have one phase per pulse. either positive or negative
useful for creating involuntary muscle contractions and pain control - biphasic currents: bidirectional flow of electrons marked by periods of non-current flow. each pulse has 2 phases (one on each side of isoelectric line)
unbalanced phases: 2 phases d not carry equal charges so there will be either positive or negative charge effect. comfortable
balanced: phases carry equal charges. normally painful
18
Q
pulse duration
A
- monophasic current: pulse duration = phase duration
- pulse duration includes horizontal distance from beginning to end of the final phase including intrapulse interval
- measures in microseconds
- pulse width determines which nerve fibers are recruited optimally
19
Q
interpulse interval
A
- time between the conclusion of one pulse and the start of another
- always longer in duration than intrapulse interval
- tissues have chance to complete mechanical events and recharge
- pulse period = one pulse + the inter pulse interval
20
Q
pulse charge
A
- measure the number of electrons contained within a pulse (area)
- each phase carries its own charge
- the higher the phase charge, the stronger the contraction
21
Q
pulse rise
A
- amount of time it takes for the pulse to reach its peak value
- if goal is to stimulate alpha neurons, you need a rapid pulse rise
22
Q
pulse trains
A
- low TENS: prevents muscle fatigue
- high TENS: prevents accommodation
23
Q
amplitude ramp
A
- ramp up: allows for gradual muscle contraction
- ramp down: allows for gradual relaxation
- gradually work patient up to stronger amplitude
24
Q
circuit series
A
- series: electrical current flows along one set route, each component has same amperage, but voltage varies. current enters body through series circuit
- parallel: electrons are provided with alternative paths to follow. electrons take the path of least resistance. once current is through skin may take different paths
25
current density
- current density is inversely proportional to the size of the electrode
- amount of current per units area
26
duty cycle
- the amount of time the current is flowing (on) as opposed to the amount of time the current is not (off)
27
electrode placement
- stimulation points:
motor points: area where the muscle is most easily excited with the minimum amount of stimulation. where motor nerve enters the muscle
trigger points: palpable nodules in taut bands of muscle fibers
acupunture points: energy that flows across the meridians is chi
28
proximity of electrodes
- too close: skin stimulation
- far enough: deeper stimulation into tissues
- too far: no specific tissues targeted
29
bipolar technique
- use of 2 electrodes, or two sets of electrodes
- equal in size, equal amounts of stimulation occurs under each electrode
- increased impedance might cause unequal stimulation
30
monopolar technique
- uses one or more active electrodes placed over the target tissue
- dispersive pad: place outside of treatment area and must be 2.5x bigger
- current density focuses under smaller electrode
31
quadripolar technique
- 2 bipolar circuits, each originating from its own channel
- channel 1: 2 electrodes same size (proximal quad)
- channel 2: 2 electrodes same size (distal quad)
- each channel has its own intensity control
32
nerve depolarization factors
1. the diameter of the nerve fiber- sensory Aβ fibers, motor nerves, Aδ and C fibers
2. the depth of the nerve fiber in relation to the electrode (the deeper the nerve the harder to depolarize)
3. the duration of the pulse or phase- (the shorter the pulse/phase, the more intensity that can be delivered)
33
stimulation levels
- subsensory: intensity is increased to the point that the patient starts to feel sensation, then reduced slightly (10%)
- sensory: intensity is increased until a slight twitch is felt, then reduced slightly
- motor: intensity is increased until visible, non-painful muscle contraction is achieved
- noxious: intensity is increased until pain fibers are stimulated
34
the law of Dubois Reymond
- current must be of sufficient intensity to cause depolarization of the cell membrane
- rate of rise of the leading edge of the pulse must be rapid (steep) enough to prevent accommodation
- duration of the current must be long enough in one direction that the nerve has time to depolarize
- sufficient time must be allowed to allow for repolarization
35
E-stem uses/goals in AT
- muscle contraction: precent atrophy, neuromuscular re-education, edema reduction
- pain control: gate control theory, noxious pain to induce descending mechanisms
- emeda reduction
36
contraindications
- cardiac dysfunction: do NOT stimulation of thorax and neck
- pacemakers: do NOT put stimulation over implant site
- pregnancy: do NOT put stimulation over back, abdomen, or pelvic girdle
- do NOT use on cancerous lesions, infected tissue, exposed metal implants, unstable fractures
37
precautions
- menstruation: stimulation over abdomen, beck, pelvic girdle may increase hemorrhage
- nerve sensitivity: carotid sinus, esophagus, larynx/pharynx, eyes, upper thorax, temporal region
- communication impairments
- severe obesity
- electronic monitoring equipment
