Object Type:
compartment
Description:
Axially asymmetric compartment. Ra is located on
one side of the compartment. This is slightly more
computationally efficient than the symmetric counterpart.
Author:
M. Wilson, Caltech (6/88)
----------------------------------------------------------------------------ELEMENT PARAMETERS
DataStructure:
compartment_type
Size:
124 bytes
Fields:
Rm
Cm
Em
Ra
inject
dia
len
Vm
previous_state
Im
initVm
[in src/segment/seg_struct.h]
total membrane resistance
total membrane capacitance
membrane resting potential
axial resistance
injected current in membrane
compartment diameter
compartment length
voltage across the membrane
Vm at previous time step
total membrane current
initial value to set Vm on reset
----------------------------------------------------------------------------SIMULATION PARAMETERS
Function:
Compartment
Classes:
segment
membrane
Actions:
INIT
PROCESS
RESET
CHECK
[in src/segment/compartment.c]
assign previous_state = Vm
update Vm, calculate Im
assign Vm = Em
make sure Rm>0, Cm>0,
Ra'>0 (if RAXIAL message is present),
Ra>0 (if AXIAL message is present)
SAVE2
RESTORE2
Messages:
CHANNEL Gk Ek
delivers the conductance and equilibrium
potential of channel within the
RAXIAL Ra Vm
AXIAL Vm
delivers the Ra and Vm of a compartment
delivers the Vm of a compartment
compartment
INJECT inject
sets the inject field to the message
EREST Em
sets the Em
value
field to the message value
----------------------------------------------------------------------------Notes:
Simulates a section of passive membrane or cable. The
potential across the membrane is given by Vm. There is a
leakage path for current through the resistance Rm. This
resistance is in series with a leakage battery Em. This
compartment can be coupled to other compartments with an
axial
resistance Ra.
The compartment is not symmetrical, with
Ra
lumped to one side of the compartment.
Any number of
ionic
channels can be introduced into the membrane (Gk, Ek in
the
circuit diagram).
injection.
The membrane also allows current
When a compartment performs its RESET action (usually
invoked by the reset command), Vm is set to the value of
the
initVm field.
Normally, initVm follows any changes to
Em,
so Vm will be initialized to Em upon reset.
If, as in
the
Hodgkin-Huxley model, Em is a leakage potential that is
different from the rest potential, initVm may be set to
the
rest potential. It will then no longer follow Em, and Vm
will be set to the rest potential upon reset.
Calculates Vm using:
dVm/dt = {(Em - Vm)/Rm + SUM[(Ek - Vm)*Gk] +
(Vm' - Vm)/Ra' + (Vm'' - Vm)/Ra + inject}/Cm
In the diagram, the compartment shown in the middle
receives the Vm' and Ra' of the upper compartment with
an RAXIAL message, and the Vm'' of the lower compartment
with an AXIAL message. Channels deliver their Gk and Ek
with a CHANNEL message.
Vm'
o_________________________________________________
|
|
|
|
|
\
/ Ra'
\
|
|
| Vm
o_________________________________________________
|
|
|
|
|
\
|
|
|
|
/ Ra
\
\
|
|
\
--/-->
/
|
___|___
|
Gk \
Rm
\
/ \
_______
Cm
|
|
|
/ A \
|
|
|
|
\ | /
|
|
Ek
--Em --\ /
|
|
------------| Iinject|
|
|
|
|
|
|
|_____________|________|________|
|
| Vm''
o_________________________________________________
|
|
|
|
|
Example:
See also:
symcompartment