A neuron is a detector, and detects what it likes, using weights on the differents inputs. The weights defines what the neuron likes. This allows the brain to have a representation system, as oppesed to a computer that have bits.
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Channels :
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Which ions enter or leaves neurons
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type specific Na+, Cl- K+ Channels
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also excitation and inhibition specific
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Electrical potential :
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amount of opposite chargs that can be attracted to that area
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diffrerence in concentration of charged particules
The membrane potential of a neuron is negative. (difference between electrical charge in the inside vs the outside)
They are channels that allows specifical ions to go when reaching a certain voltage threshold
- Resting potential
- -70mV
- when no inputus and steady state of stimulation
- Action potential
- electrical pulse sent down the axon when the membrane potential exceeds a certain threshold
- 1 Balance of electric and diffusion forces
- 2 Principal ions (K+ Na+ Cl-)
- 3 Equilibirum channel potentals
- 4 Integretaion equations
- 5 The overall membrane equilibirum potential
Ions have different charges : Na+, Cl-, K+, Ca++. Without calcium there would be no learning.
The ions have to go through ions channel to go in/out of the cell. The smaller the size of the channel is, the higher the resistance is, and the greater the voltage is needed to pass the same amount of current.
I = V * G (Ohm's law with conductance)
Constant motion in fine evens out distribution => Second law of thermodynamics
Even the charges are balanced electricaly, there can still be a flow of ions because of the difference of concentration between in and out.
E = Equilibrium channel potential = amount of electrical potentail V needed to conteract diffusion.
I = G * (V - E)
If V == E, the current will be zero, meaning that the diffusion force is conteracted by the voltage exactly.
Also called Reversal potential (because current reverses on either side of E)
- eg V < E => negative value for current, meaning the current flow will reverse.
Each ion channel has its own equilibrium potential because of the different concentration of the ions.
| Label | Definition |
|---|---|
| Vm | membrane potential (difference insede vs outside) |
| Conductance (G) | Opposite of the resistance (1/R) |