Electrical Synapses
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Transcript of Electrical Synapses
• Relatively non-specific.• Molecular movement through passive diffusion.• Selectivity based upon molecular size (- allow movement of molecules whose molecular weight <1000Da.) (- allow movement of molecules whose diameter < 1.2nm.)
Cell #1Cell #1 Cell #2Cell #2
Gap junctionsGap junctions
Structural arrangement of Gap junctionsStructural arrangement of Gap junctions
ConnexinConnexon
( A hemi-channel)
Structural arrangement of Gap junctionsStructural arrangement of Gap junctions
Two docked connexons(a gap junction channel)Gap junction plaque
Electric synapses Electric synapses vs.vs. Chemical synapses Chemical synapses
Synaptic Synaptic delaydelay
No delay0.2ms-2ms
Direction of Direction of conductanceconductance
Bi- directional, but not necessarily symmetric
unidirectional
Two coupled cells in VitroTwo coupled cells in Vitro
Cell 2
Cell 1
II22II11
The equivalent electrical circuitThe equivalent electrical circuit
r1
rc
r2
Cell 2Cell 1
V1V1 V2V2
The equivalent electrical circuitThe equivalent electrical circuit
V1V1
I2I2I1I1V2V2
The equivalent electrical circuitThe equivalent electrical circuit
r1
rc
r2
Cell 2Cell 1
V1V1 V2V2
Basic conceptsBasic concepts
I1, I2
V11,V22, V21, V12
V 1 1
Voltage in cell Current injected to cell
r1
rc
r2
Cell 2Cell 1
V1V1 V2V2
Input resistancesInput resistances
21
21
1
1111
)(
rrr
rrr
I
VR
c
c
r1
rc
r2
Cell 2Cell 1
Input resistancesInput resistances
21
12
2
2222
)(
rrr
rrr
I
VR
c
c
If rc << r2 and rc << r1
Then 21
212211 rr
rrRR
r1
rc
r2
Cell 2Cell 1
Transfer resistancesTransfer resistances
1
2121 I
VR
2
1212 I
VR
r1
rc
r2
Cell 2Cell 1
r1
rc
r2
Cell 2Cell 1
21
121221 rrr
rrRR
c
Cell 2Cell 1 Cell 2Cell 1
Coupling coefficientsCoupling coefficients
Potential in un-injected cell
Potential in injected cell
rrV
VCCc
2
11
2112
1
1
rrV
VCCc
1
22
1221
1
1
A typical traceA typical trace
I1
V11 V12
V21 V22
I2
Cell 2Cell 1Traces!Traces!
0 0.5 1.0 1.5 2.0
-0.5 nA, injected to cell 2 (left cell).
Cell1Cell1
Cell2Cell2
Cell 2Cell 1
-0.5 nA, injected to cell 1 (right cell).
Traces!Traces!
Cell1Cell1
Cell2Cell2
Cell 2Cell 1
Cell1Cell1
Cell2Cell2
Traces!Traces!
+0.4 nA, injected to cell 2 (left cell).
Cell 2Cell 1
accommodation
summation
Traces!Traces!
+0.4 nA, injected to cell 2 (left cell).
Cell1Cell1
Cell2Cell2