Passive Membrane Properties Flashcards
What is capacitance?
Membrane has a capacity to absorb a charge difference
Larger surface area = more capacitance
What are the 3 main passive properties of neurons?
Resting membrane electrical resistance, membrane capacitance and intracellular axial resistance
What happens when a current is injected into a neuron?
Voltage changes and rises more slowly due to capacitance
Define time constant.
Time it takes following injection of current for the potential to change by 63% of its final value
How will a cell respond to an injected curremt?
It will depolarise
How will a cell respond to an outward current?
It will hyperpolarise
What does membrane resistance affect?
The magnitude of electrical signals
What type of relationship is between the amplitude of the voltage change achieved and the current injected?
Linear relationship
What is Ohm’s law?
Change in V = I x R
What affects leaking and ability to absorb charge?
Membrane thickness and diameter of conducting cable (axon)
What happens if the axon has a large diameter?
Lower the resistance of the axon and the less it will ‘leak’ (more efficient)
What affects efficiency?
Axial resistance and membrane resistance
What affects speed?
Axial resistance and capacitance
Define length constant.
Distance from the site of current injection where the potential has fallen by 37% of its original value
What does the length constant indicate?
How far a depolarizing current will spread along the axon
