Prev: Compartments Contents Next: Synapses

Chapter 6: Channels

Channels line the cell membrane and influence the cell's behavior. There are many types of channels. So far, three channels from the K+ family have been implemented in NCS. These are the m-channel, the a-channel, and the ahp-channel abbreviated Km, Ka, and Kahp, respectively.
KeywordValueDescription
CHANNEL
family(string)
Starts a channel definition section. The family value given indicates what kind of channel is to be created.
The current available choices are Km, Ka, and Kahp. Each has some exclusive parameters listed in each's subsection.
More families will be added at a later date.
TYPE
name(string)
The name which this channel will be refered to in the input file
M_INITIAL
mean(real)
stdev(real)
The activating (m) value of the channel
M_POWER
mean(real)
stdev(real)
When the m value is used, it is raised by the M_POWER
m^M_POWER
REVERSAL_POTENTIAL
mean(real)
stdev(real)
Used in calculating a channel's current status.
Its contribution to the equations is determined by Channel type
UNITARY_G
mean(real)
stdev(real)
Used in calculating a channel's current status.
Is used as a multiplier for all Channels.
STRENGTH
mean(real)
stdev(real)
Used in calculating a channel's current status.
Is used as a multiplier for all Channels.
END_CHANNEL
N/A
Indicates the completion of a channel definition section.

Km channels

M-Channels (Km) have only an activation particle (m). Inhibits its parent cell from reaching threshold.
KeywordValueDescription
E_HALF_MIN_M
mean(real)
stdev(real)
SLOPE_FACTOR_M
(real)(real)
(real)
TAU_SCALE_FACTOR_M
mean(real)
stdev(real)

Example

CHANNEL Km
        TYPE                            m
        M_INITIAL                       0.0             0.0
        REVERSAL_POTENTIAL              -80             0
        M_POWER                         1
        E_HALF_MIN_M                    -44
        SLOPE_FACTOR_M                  40 	20	8.8
        TAU_SCALE_FACTOR_M              0.303
        UNITARY_G			5
        STRENGTH                        0.00015
END_CHANNEL

Kahp channels

AHP-Channels or After Hyper Polarization Channels (Kahp) are voltage independant but Calcium dependant.
KeywordValueDescription
SEED
value(integer)
The seed to be used to generate random numbers for this channel object
CA_SCALE_FACTOR
mean(real)
stdev(real)
CA_EXP_FACTOR
mean(real)
stdev(real)
CA_HALF_MIN
mean(real)
stdev(real)
CA_TAU_SCALE_FACTOR
mean(real)
stdev(real)

Example

CHANNEL Kahp
        TYPE                            ahp1
        SEED                            999999
        M_INITIAL                       0.0             0.0
        REVERSAL_POTENTIAL              -80             0 
        M_POWER                         2
        UNITARY_G			6
        STRENGTH                        0.00015
        CA_SCALE_FACTOR                 0.000125
        CA_EXP_FACTOR                   2
        CA_HALF_MIN                     2.5
        CA_TAU_SCALE_FACTOR             0.01
END_CHANNEL

Ka channels

A-Channels (Ka) help the cell deal with bacground noise. Has both an activation (m) and an inactivation (h) particle.
KeywordValueDescription
H_INITIAL
mean(real)
stdev(real)
H_POWER
mean(real)
stdev(real)
E_HALF_MIN_M
mean(real)
stdev(real)
E_HALF_MIN_H
mean(real)
stdev(real)
SLOPE_FACTOR_M
mean(real)
stdev(real)
SLOPE_FACTOR_H
mean(real)
stdev(real)
V_TAU_VALUE_M
values+(real)
V_TAU_VOLTAGE_M
values+(real)
V_TAU_VALUE_H
values+(real)
V_TAU_VOLTAGE_H
values+(real)

Example

CHANNEL Ka
        TYPE                            a
        M_INITIAL                       0.0             0.0
        H_INITIAL                       1.0             0.0
        REVERSAL_POTENTIAL              -80             0
        M_POWER                         1
        H_POWER                         1
        E_HALF_MIN_M                    11
        E_HALF_MIN_H                    -56
        SLOPE_FACTOR_M                  18
        SLOPE_FACTOR_H                  18
        UNITARY_G			0.12
        STRENGTH                        2.5
        V_TAU_VALUE_M                   0.0002		9999
        V_TAU_VALUE_H                   0.03	0.08	0.13	0.18	0.23
        V_TAU_VOLTAGE_M                 100
        V_TAU_VOLTAGE_H                 -21	-1	10	21
END_CHANNEL
Prev: Compartments Contents Next: Synapses
Last updated Monday 6/5/2006