Object Type:
symcompartment
Description:
Axially symmetric compartment. Ra is divided into
two equal components across the compartment.
Author:
M. Wilson, Caltech (6/88)
----------------------------------------------------------------------------ELEMENT PARAMETERS
DataStructure:
symcompartment_type
Size:
132 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:
SymCompartment
[in src/segment/symcompartment.c]
Classes:
segment
membrane
Actions:
INIT
PROCESS
RESET
assign previous_state = Vm
update Vm, calculate Im
assign Vm = Em, set internal constants
depending on the types of incoming
CHECK
SAVE2
RESTORE2
make sure Rm>0, Cm>0, Ra>0
CHANNEL Gk Ek
delivers the conductance and equilibrium
potential of channel within the
INJECT inject
sets the inject field to the message
EREST Em
sets the Em
messages.
Messages:
compartment
value
field to the message value
CONNECTHEAD
Ra Vm
used to connect to the child
CONNECTTAIL
Ra Vm
used to connect to the parent
CONNECTCROSS
Ra Vm
used to cross-connect the first
compartments after a binary or
compartment
compartment
multiple
CONNECTSPHERE Ra Vm
branch.
connects a cylinder to a sphere; is
symmetric (i.e. may be used for both
directions). Assumes that all the
dendrites are distributed perfectly
over
the soma/sphere.
Using CONNECTHEAD
or
CONNECTTAIL instead connects all
denrites
RAXIAL Ra Vm
AXIAL Ra Vm
to one point on the soma/sphere.
alias for CONNECTTAIL
alias for CONNECTHEAD; note that for the
asymmetric compartment, AXIAL only
RAXIAL2 Ra Vm
RAXIALC Ra Vm
RAXIALS Ra Vm
alias for CONNECTHEAD
alias for CONNECTCROSS
alias for CONNECTSPHERE
receives Vm.
----------------------------------------------------------------------------Notes:
Like the compartment object, the symcompartment 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, and there is a membrane
capacitance in parallel with Rm and Em. This compartment
can
be coupled to other compartments with an axial resistance
Ra,
which is divided into two pieces of resistance Ra/2 on
either
side of the point having the potential Vm.
In most
respects,
the symcompartment is similar to the asymetric
compartment
object, and its use is more fully described in the
documentation for compartment. However, the division of
Ra
requires different messages to be used when linking
symcompartments.
For linear chains of symmetric compartments, all of the
connection messages are equivalent, and all compartments
may
be linked by exchanging RAXIAL messages. However, for
branched structures, the the incoming current must be
calculated differently, depending on whether it is from a
parent, child, or connected sibling in the tree of
compartments, using the messages described above.
Because of
this added complexity, it is best to use the readcell
routine
with a cell parameter file when constructing cells with
symcompartments. This will link the compartments with
the
proper messages.
Example:
from
Use the showmsg command to examine the messages to and
/CA3/soma, /CA3/apical_10, /CA3/basal_8, etc. in the
traub91
simulation.
See also:
compartment, readcell