Passive Properties Flashcards
What three positive properties properties are important to electrical signaling?
- Membrane resistance
- Axial resistance
- Membrane capacitance
How can you adjust passive properties to promote fast signaling?
- Increase membrane resistance.
- Lower axial resistance.
- Lower membrane capacitance
Are passive signals (local graded potentials), hyper or depolarizing?
Both
Are active signals (action potentials) hyper or depolarizing
Depolarizing
How do they record membrane potential?
Stimulating electrode and recording oscilloscope
Why does injecting a positive current result in depolarization?
When you inject a positive current you inject positive ions into the negative cell, making it less negative.
When you inject positive current, what is being measured?
The current that leaves the cell
Why does the membrane potential change more slowly than the current pulse?
The lipid bilayer holds onto some charge in the beginning.
What determines the change in membrane potential?
Membrane (input) resistance
How does neuronal size affect input resistance?
Larger equals more surface area. More surface area equals more channels. More channels lowers input resistance.
What is specific membrane resistance?
Property of membrane independent of size of the cell. Does depend on axon diameter though.
What is specific membrane capacitance?
Capacitance independent of size of the cell. Does depend on axon diameter though.
How does neuronal size affect input capacitance
Larger size equals more space for storage. More space equals more charge.
What is membrane current?
Total current
What is ionic current?
Current that goes through ion channels
What is capacitive current?
Current that goes onto lipid bilayer (capacitator)
What is membrane time constant?
The time it takes to reach 63% of possible ionic current. Determines the time when the potential change reaches 63% of its value.
How does size of cell body influence triggering an action potential?
If cell body is smaller, membrane (input) resistance is bigger. Which means that there can be a bigger change in membrane potential (better chance of clearing threshold).
What is a better transmitter: axons or undersea cables?
undersea cables
What is length constant?
The distance from the site of current injection, where potential reaches 37% of its original value
What determines the value of initial peak potential?
Input resistance and current
How can you speed up conduction velocity?
Increasing length constant while decreasing time constant?
How do neurons speed up electrical signal propagation?
- Myelination (increases membrane resistance)
- Increase axon diameter
