Nervenmodelle (neuron modeling-101.186)- exam questions

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Nervenmodelle (neuron modeling-101.186)- exam questions

Beitragvon Hofi » 03.06.2014, 17:30


Oral examination:

(1) unmyelinated vs myelinated. Tell me something about it.

Capacity and resistance change when myelinated. AP can jump due to insulation swann cell layers. If the swann cell wraps around once,
there will be a threfold membrane layer (each side of cell+axon). Therefore an increased membraneresistance and no loose of current. If it wraps around, let`s say 10 times, we would have a 10*2+1=21 part thick layer and therefore even higher increased resistance. That`s why the assumption of an insulator holds here.

(2) Tell me something about refractory.

No answer here. But I would say there are two kinds of refraction: absolute and relative. While during the first you cannot greate another action potential due to the inactive behavior of the sodium channels, you have relative refractory afterwards. There you need a much higher stimulus for a lower AI, but you can generate them. Maybe more needed to be known here...

(3) Tell me something about the Nernst & Goldmann equations.

Write down both. Explain what pk and the others stand for- permeabilities in cm/sek. The Nernst is made up by the assumption of an steady equilibrium between osmotic and electric work. Therfore integral 1/V dV gives the lg. of the volumes. Together with n=c/V this gives lg(c2/c1). and so on.

(3-1) Where can we approximate the Goldman equation with the Nernst equation?

This can be done if one is interested in the membrane resting potential. Since the permeability of potassium is much higher then the others (it`s the driving value in this equation), the Nernst- voltage for potassium only (-80mV) gives quite a good approximation for the membrane resting potentail.

(4) Do you know any other models beside the HH?

No real answer here.
but assumed that if you say: Yes, the frog- FE model, rabbit- CRRSS, rat- SE, human- SRB?, mathematical- Fitzhug (V=-25mV *[x-1,2] for the membrane potential).
Only HH is influenced by the head block (not useable for temperatures higher then 32°C). And then be able to loose some words about each model. The differences, the assumptions needed for programming those.

(5) What can you tell me about the phase diagramm in the Fithoug modell?

No answer here. But you can look it up yourself online, or in the picture book. More infos on WIkipedia: ... gumo_model

(6) Explain the patch clamp technique.

A small class pipette used. This is so small, that preferable you have single ion channels that you take a closer look at. Vakuum needed between the membrane and the clamp for good fixation. Can also be done on living cells. See picture book, page 13, left upper corner.

(7) Draw the equvalent curcuit for the HH model and write down the HH equations. Why is h called the innactivation variable?

Write down the equations for d/dt (V)= 1/c * [IK+...+IL] and d/dt (V)= [-gNa*m³*h*(...)+...]*(...)
The equivalent circuit is the one where a resistor (for the conductivity of the membrane) and a capacitor (capacitance) are parallel. Since HH

What is the activation function?
Will be described later...

More about the exam and how to prepare soon. I also try to upload my preperation in the next days and additional questions when I di it in two weeks.

Beiträge: 107
Registriert: 07.11.2010, 11:23

Re: Nervenmodelle (neuron modeling-101.186)- exam questions

Beitragvon Hofi » 16.10.2014, 14:44

And attached the summary I made for the exam. The exam can be taken each Monday at Prof. Rattay´s new room in 6th floor, Tower A, Freihaus.
It´s a really nice exam and if you know the differences between the models, then you are positive.
Du hast keine ausreichende Berechtigung, um die Dateianhänge dieses Beitrags anzusehen.

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