Where are these connections "anatomically" located in the HH model?

  • Thread starter somasimple
  • Start date
  • #1
somasimple
Gold Member
760
5
Hi,

Here is a basic picture of the famous electric circuit of the HH model.
Can someone please tell me the anatomical locations of the connections marked in red in the cell?
Thanks.
 

Attachments

  • Hodgkin-Huxley_01.png
    Hodgkin-Huxley_01.png
    6.2 KB · Views: 79

Answers and Replies

  • #2
BillTre
Science Advisor
Gold Member
2022 Award
2,213
7,348
Could not enlarge picture. Please post anew one.

Since it has something to do with Hogkin-Huxley its probably a circuit based on membrane components.

The capacitor I can make out. It represents the membrane capacitance. Charges on ether side of the membrane act as if they are charges on either side of a capacitor.
The battery symbols represents the reversal potential for each species of ion, which drives the currents of each different ion species.
Can't tell what the other symbols are. Picture is too small. Can't read the text.

Overall it is a circuit diagram representing how membrane currents and voltages are affected by the ions and transmembrane conductances.

OK, the picture is working for me now.
What do the subscripts "n" and "L" mean based on where this can from?
The round thing at the right seems to be a current meter, with the subscript "p". What does "p" mean?
 
  • #3
somasimple
Gold Member
760
5
Hi,
The picture comes from there
https://en.wikipedia.org/wiki/Hodgkin–Huxley_model
Normally the resistors (ion channels) which are symbolised here are connected between the external medium and the inside of the cell because they are enclosed in the membrane.
The capacity, too.
The battery is created by a gradient between the outside and the inside (Nernst), isn't it?
So for me, the diagram doesn't fit.
 
  • #4
atyy
Science Advisor
14,789
3,333
The points in red do not correspond to an anatomical location in the cell. It is the combination of the resistor and the battery in series that represents an ion channel, since opening an ion channel decreases the membrane resistance and also generates a voltage. So the circuit diagram is not physically correct in a fundamental sense, but is a helpful analogue to the form of the equations (derived by considering the physics of the Nernst equation).

Incidentally, the HH equation is also different in form from the GHK equation (which is probably more correct in term of fundamental physics), but the HH equation has a more convenient analytical form and is an extremely good approximation in most of the physiological range.

However, there are times when the GHK equation is more accurate.
 
  • Like
Likes somasimple, madness and BillTre
  • #5
BillTre
Science Advisor
Gold Member
2022 Award
2,213
7,348
The capacitor is the membrane, which separates the different charges on either side of the electrically polarized membrane.
The resistor (don't know why its in a box) combined with the battery represent the current through the membrane channel (composed of certain ions) that is driven by the combined reversal potentials of the ions that can go through that particular channel. The resistance is variable in that it has open or closed states.
 
  • #6
madness
815
70
I'm at risk of repeating what others have said here, but there might be a couple of extra points I can make. The capacitance is essentially due to the lipid bilayer of the membrane, which allows charge to accumulate on either side. The resistance/conductance is essentially determined by the ion channels through which certain ions can flow. The battery is caused by a concentration difference across the membrane (of multiple different ionic species). Ions flow both due to voltage and concentration differences across the membrane, and different channels have different permeability to different ions. Finally, the concentration difference of the various ionic species is maintained by active transport of ions across the membrane by specialised proteins, which use ATP as an energy source.
 

Suggested for: Where are these connections "anatomically" located in the HH model?

Replies
3
Views
524
  • Last Post
Replies
19
Views
3K
  • Last Post
Replies
6
Views
871
Replies
3
Views
516
  • Last Post
Replies
19
Views
1K
  • Last Post
2
Replies
46
Views
3K
  • Last Post
Replies
5
Views
624
Replies
1
Views
435
Replies
3
Views
747
Replies
100
Views
5K
Top