Non-Systems: Therapeutic Modalities: Electrical Agents: Basic Concepts Flashcards
1
Q
Resting Membrane Potential: Electrical Potential
A
- Electrical potential is generated by the higher concentration of potassium inside the cell as opposed to sodium outside the cell.
2
Q
Resting Membrane Potential: Charges
A
- Inside the cell=negative
- Outside the cell=positive
Due to the movement of potassium out of the cell
3
Q
Resting Membrane Potential: Excitable cells
A
- RMP will be -60 to -90
4
Q
Resting Membrane Potential: Maintained by
A
- An active sodium potassium pump that takes in potassium and extrudes sodium
5
Q
Action Potential
A
- Generated when the influx of sodium into the cell causes a reduction of resting membrane potential called depolarization
6
Q
Action Potential: Critical Threshold
A
- Point at which sodium/potassium pump opens widely
- Permeability to sodium increases rapidly
- Permeability to potassium occurs slowly
- (-55mV)
7
Q
Action Potential: Depolarization
A
- Transmembrane potential rises to +35 mV
- Positive charge generated inside the cell
- Negative charge generated outside the cell
8
Q
Action Potential: Repolarization
A
- Potassium channels maximally open at the time the sodium channels close
- Potassium rushes out of cell
- Transmembrane potential becomes rapidly more negative
9
Q
Action Potential: Hyperpolarization
A
- Potassium channels remain open long enough to repolarize the membrane
- Potassium channels then close and passive diffusion of the ions rapidly return to its initial value
10
Q
Electrical Action of Muscle and Nerve
A
- Amplitude must be high enough to cause membrane potential to be lowered enough to reach threshold
- Duration must cause depolarization (usually less than or equal to 1 ms)
- Rate of rise of current must be rapid enough to prevent accomodation
11
Q
Rheobase
A
- Intensity of current with long duration stimulus required to generate minimum muscle contraction
12
Q
Chronaxie
A
- The pulse duration of the stimulus at twice the rheobase intensity
- In denervated muscle=greater than 1 msec
13
Q
Pulse Durations: Short (Less than 0.05 msec)
A
- Stimulate sensory nerves
14
Q
Pulse Durations: Longer (Greater than 1 msec)
A
- Stimulate motor nerves
15
Q
Pulse Durations: Long (Greater than 10 msec)
A
- Stimulate denervated muscle
