Dendritic Integration Flashcards
1D model of chemical signals
t = x^2/2D
t = time constant
x = displacement in one dimension in time
D = diffusion coefficent )10um^2/s)
limitations of the 1D model
diffusion is inefficent
therefore use electrical signals (1m in 10ms)
cable theory of neurons
resistor of core is the cytoplasm
signal dissipates away from core
capacitor - charge builds up on both side of core
insulation - membrane can be leaky
what is the length constant
how far something travels?
distance over which voltage decays to approx 37% (1/e) its initial value
factors which influence length constant
Ri - axial resistance unit length of cable
Rm - membrane resistance of unit length of cable
Cm - capacitance of unit length cable
how to increase length constant
increase Rm (better insulated cable)
decrease Ri (better conducting inner core)
why does the soma have a slower EPSP
more membrane to depolarise
EPSP amplitude at the dendrites
bigger at the thinner distal inputs
EPSP amplitude at the soma
smaller and slower further away from a dendrite
temporal and spatial summation
temporal summation - multiple inputs from a single neuron (time dependent) -long time constant for AP
spatial summation - inputs from mutiple/several neurons - long length for AP
what does cable filtering at the dendritic EPSPs cause
decreases amplitude at soma and slows time course at soma
where are inputs integrated
at the axon initial segment
synaptic integration
independent of CA1 neurons in hippocampus (except neocortical layer 5 pyramidal neurons)
why do distal dendrites have a large amplitude
more AMPA receptors
HCN1 expression
expressed differentially along dendrites
