mirror of
https://gitlab.gwdg.de/j.hahn02/university.git
synced 2026-01-01 06:44:25 -05:00
refactor various files
This commit is contained in:
107
S2/Neuro/VL/NeuroVL2.typ
Normal file
107
S2/Neuro/VL/NeuroVL2.typ
Normal file
@@ -0,0 +1,107 @@
|
||||
#import "../preamble.typ": *
|
||||
|
||||
#show: conf.with(num: 1)
|
||||
|
||||
= Membrane Potential
|
||||
|
||||
Outside the cells in the brain there is salt.
|
||||
Inside there is potassium.
|
||||
|
||||
== Prerequisites for a Neuron to fire
|
||||
|
||||
_Watch the embedded movie._
|
||||
|
||||
There are different potentials build up in the membrane.
|
||||
|
||||
+ The charge is in equillibrium. But there is a gradient of Pr and Cl
|
||||
+ Cloride will diffuse $==>$ on that side there are too many negative charges
|
||||
+ The negative charge pushes the potassium to this side
|
||||
+ Finally a potassium gradient stabilizes
|
||||
|
||||
Why is the resulting potential negative?
|
||||
|
||||
== Nernst and general Nernst eqation
|
||||
$
|
||||
V_(x) = (R T) / (z F) ln ([X]_(o) ) / ([X]_(i) ) \
|
||||
V_(x) = (R T) / (z F) ln (P_("K") [K]_(o) + P_("Cl") ["Cl"]_(o) + ... ) / (P_("K") [K]_(i) + P_("Cl") ["Cl"]_(i) + ... ) \
|
||||
|
||||
$
|
||||
|
||||
When the permeability for the potassium is low then the other ones play a bigger role.
|
||||
Potential is only there when permeability is existing.
|
||||
|
||||
Q: What is similar to a low pass filter.
|
||||
|
||||
In reality there are multiple conducters connected in parralel. Also the conductivity of the Na and K channles are changable.
|
||||
|
||||
Q: What does a conductivity of $oo$ mean?
|
||||
|
||||
= Hodgkin and Huxley
|
||||
|
||||
Q: What have they done?
|
||||
A: They used squids to measure the axons, because they are $1"mm"$ thick
|
||||
|
||||
Types of Neuronal Recording Methods
|
||||
- EEG (on top of the head)
|
||||
- ECoG (small hole in the head)
|
||||
- Extracellular (needles in the brain)
|
||||
- Intra cellular (needles in the cell of the brain)
|
||||
|
||||
== Action Potential
|
||||
|
||||
+ The cell gets excited
|
||||
+ Chainreaction of channel opening and gradient stabilisation
|
||||
- Sodium channels open
|
||||
- K chanels open
|
||||
- Na channels become refactory
|
||||
- ...
|
||||
+ Refactory period
|
||||
+ ...
|
||||
|
||||
#highlight[TODO: continue the steps]
|
||||
|
||||
Currents can add up to trigger an AP. THe refactory period is the time after an AP when Na channles are inactive. The firing rate is increaed with a highter input strenght.
|
||||
|
||||
The lenght of the potiential depends on the type of cell. Then the refactory period is also longer. \
|
||||
The maximum firing rate is limited by the absolute refactory period.
|
||||
|
||||
== The actual model
|
||||
|
||||
$
|
||||
I_("inj") = I_(C) + sum I_(k) (t) , space C = Q/u , space I_(C) = C (dif u) / (dif t) = C (dif V) / (dif t) \
|
||||
I_(x) = I_(x) \
|
||||
C (dif V_m ) / (dif t) = - sum I_(k) + I_("inj") (t) \
|
||||
sum I_k = g_("Na") (V_m - V_("Na") )+ g_(K) (V_m - V_(K) )+ g_(L) (V_(m) - V_(L) )\
|
||||
C (dif V_m ) / (dif t) = - g_("Na") (V_m - V_("Na") )- g_(K) (V_m - V_(K) )- g_(L) (V_(m) - V_(L) ) + I_("inj") (t) \
|
||||
$
|
||||
|
||||
Now the Equation becomes time dependent
|
||||
|
||||
$
|
||||
C (dif V_m ) / (dif t) = - macron(g)_("Na") m^(3) h (V_m - V_("Na") )- macron(g)_(K) n (V_m - V_(K) )- macron(g)_(L) (V_(m) - V_(L) ) + I_("inj") (t). \
|
||||
dot(x)= - (1) / (tau_(x) u_(b)) A .
|
||||
$
|
||||
|
||||
Capacitance is a biological constant.
|
||||
|
||||
== Voltabe clamp method
|
||||
|
||||
With this method it is possible to stimulate a cell and measure the floating current at the same time.
|
||||
|
||||
There are substances to kill certain types of channels in the cell. If done so the graph of the potential changes.
|
||||
|
||||
Also there is a method to measuer individual channels and their current they leave through.The AP is a positive feedback loop.
|
||||
|
||||
The sodium channels cannot immeadiately open again. It takes about 1ms for them to open again. When measuring one always measurers multiple fibres (Suberposition).
|
||||
|
||||
In the heart there are calcium channels.
|
||||
|
||||
_Max firing frequency is about $1"kHz"$_
|
||||
|
||||
== Propagation of AP
|
||||
|
||||
There are multiple Methods of propagation the AP. One is to recreate the AP along the way (this takes time but is faster with higher diameter of the axon).
|
||||
|
||||
The other method is the saltatory "jumpy" conduction. This is much faster and the AP jumps between the isolations.
|
||||
|
||||
|
||||
20
S2/Neuro/preamble.typ
Normal file
20
S2/Neuro/preamble.typ
Normal file
@@ -0,0 +1,20 @@
|
||||
#import "../../default.typ": *
|
||||
|
||||
#let rot = math.op("rot")
|
||||
#let grad = math.op("grad")
|
||||
|
||||
#let conf(num: none, date: "", body) = {
|
||||
// Global settings
|
||||
show: default
|
||||
|
||||
// Set the header
|
||||
[ExPhy II \ Vorlesung #(num) \ #(date) \ Jonas Hahn]
|
||||
|
||||
// Make the outline
|
||||
outline()
|
||||
|
||||
// load the document
|
||||
body
|
||||
}
|
||||
|
||||
|
||||
@@ -1,4 +1,4 @@
|
||||
#import "./preamble.typ": *
|
||||
#import "../preamble.typ": *
|
||||
|
||||
#show: conf.with(num: 1)
|
||||
|
||||
|
||||
Reference in New Issue
Block a user