Electrical Stimulation Part 1 Flashcards
Charge:
loss or gain of electrons, measured in coulombs
Polarity:
cathode (-) anode (+) Attraction/repulsion forces = electric field. Alkaline reactions under the cathode softens underlying tissues.
The medication is (+) what charge should the machine be to drive the medication into the body
(+); like polarities repel each other
Voltage:
driving force that moves electrons, a measure of potential energy
Conductor examples:
water, metal, nerves; anything that helps the electrons along their way
Insulator examples:
rubber, plastic, fat; anything that inhibits the transmission
Properties of electrically excitable cell
resting membrane potential (RMP) -70mv usually, Action Potential, Propagation of an Action Potential (movement of the action potential along the nerve)
The cell membrane is more permeable to _____ in comparison with _____________ and negatively-charged proteins (anions).
potassium (K+), sodium (Na+)
An electrical potential is generated across the cell membrane due to the higher concentrations of K+ and anions on the ____ of the cell relative to the concentration of Na+ on the ____
inside, outside
A ____ charge is produced within the cell and a positive charge develops on the outside of the cell as the ____ charged K+ diffuses from the cell
negative, positive
RMP is ____mV to ____mV for excitable cells
-60, -90
RMP is maintained by:
an active sodium potassium pump that takes in K+ and extrudes Na+
A stimulus causes the cell membrane to become more ____ to ___ ions
permeable, Na+
An action potential is generated when the influx of ____ causes a reduction of RMP which occurs slowly at first. Reduction in the RMP is called _____.
Na+, depolarization
When transmembrane potential reaches a critical threshold level (approximately ____mV), the voltage-sensitive Na+ and K+ channels ___.
-55, open widely
Permeability to Na+ increases _____, whereas the permeability to K+ increases _____.
rapidly, slowly
During depolarization, transmembrane potential might rise as high as ____mV. A positive charge is generated inside the cell and a negative charge outside is produced, as a result of the flow of ions.
+35
The ___ channels are fully open about the time the ___ are closed and ___rushes rapidly out of the cell, making the transmembrane potential progressively more negative. This process is repolarization.
K+, Na+, K+
The ____ channels remain open long enough to repolarize the membrane (_________mv <RMP). This is called hyperpolarization.
K+, 10-20
The ____ channels close and passive diffusion of the ions ____ returns the RMP to its initial level.
K+, rapidly
Opening of the Na+ and K+ channels and voltage changes that produce a AP at one segment of the membrane triggers successive depolarization in adjacent regions of the ____, _____, or ____
nerve, muscle, membrane
AP movement occurs along the ____ of the nerve or muscle cell
surface
Movement of the AP along an unmyelinated nerve is generated via sequential depolarization (____) along neighboring sites in the nerve membrane.
eddy currents
Speed of conduction in ____ diameter fibers is ____ because of the greater internal resistance in the small fibers.
small, slow
In myelinated nerve fibers, ______ conduction occurs at discrete junctures (_______) in the myelin sheath which surrounds the nerve
salutatory, nodes of Ranvier
What is the sequence of nerve conduction
- Conduction of an action potential. An action potential is generated as Na+ ions flow in at one location along an axon. 2. The depolarization spreads to the neighboring region of the membrane, initiating an action potential there. 3. The original region repolarized as K+ ions flow out. 4. The depolarization-repolarization process is repeated as the action potential is propagated down the axon.
