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Electrical Properties of Neurons
• Rest potential
• Passive membrane properties
• Voltage-dependent (active) membranes
2.2 Recording passive and active electrical signals in a nerve cell. (Part 1)
2.2 Recording passive and active electrical signals in a nerve cell. (Part 2)
Different ions determine the membrane potential
“Passive” = all “g’s” are constant.
• Temporal properties
Membrane time constant
Membrane time constant = “tau” membrane
Voltage response
Current injection
Membrane time constant
The membrane time constant affects signal integration
Tau membrane depends on capacitance and resistance
τ = RC = C/G
How does it depend on neuron size?
d
S = 4πd2
C~S
G~S
Therefore: if the neurons have similar specific conductance and
capacitance, the time-constants will be equal regardless of the
diameter.
D
Neurons are not iso-potential
• Spatial properties
Passive propagation of signals
Dendrites as passive electrical cables
Real dendritic morphology
(hippocampal interneuron)
Cable representation for simulations
Dendrites as passive electrical cables
Dendrites as passive electrical cables
d ⋅ Rm
λ=
4 ⋅ Ra
Rm - membrane resistivity
Ra – axial resistivity
Dendrites as cables (steady state)
λ=
d ⋅ Rm
4 ⋅ Ra
Box C Passive Membrane Properties (Part 1)
Dendrites as cables
Spatial and temporal integration in dendrites
Temporal and spatial summation in passive membranes
Also in axons
Passive membranes also in axons
3.10 Passive current flow in an axon. (Part 2)
3.10 Passive current flow in an axon. (Part 1)