<s>
In	O
physiology	O
,	O
electrotonus	B-Algorithm
refers	O
to	O
the	O
passive	O
spread	O
of	O
charge	O
inside	O
a	O
neuron	O
and	O
between	O
cardiac	O
muscle	O
cells	O
or	O
smooth	O
muscle	O
cells	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potential	I-Algorithm
(	O
or	O
graded	B-Algorithm
potential	I-Algorithm
)	O
,	O
a	O
non-propagated	O
local	O
potential	O
,	O
resulting	O
from	O
a	O
local	O
change	O
in	O
ionic	O
conductance	O
(	O
e.g.	O
</s>
<s>
Action	B-Algorithm
potential	I-Algorithm
,	O
a	O
propagated	O
impulse	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
represent	O
changes	O
to	O
the	O
neuron	O
's	O
membrane	O
potential	O
that	O
do	O
not	O
lead	O
to	O
the	O
generation	O
of	O
new	O
current	O
by	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
However	O
,	O
all	O
action	B-Algorithm
potentials	I-Algorithm
are	O
begun	O
by	O
electrotonic	B-Algorithm
potentials	I-Algorithm
depolarizing	O
the	O
membrane	O
above	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
which	O
converts	O
the	O
electrotonic	B-Algorithm
potential	I-Algorithm
into	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
Neurons	O
which	O
are	O
small	O
in	O
relation	O
to	O
their	O
length	O
,	O
such	O
as	O
some	O
neurons	O
in	O
the	O
brain	O
,	O
have	O
only	O
electrotonic	B-Algorithm
potentials	I-Algorithm
(	O
starburst	O
amacrine	O
cells	O
in	O
the	O
retina	O
are	O
believed	O
to	O
have	O
these	O
properties	O
)	O
;	O
longer	O
neurons	O
utilize	O
electrotonic	B-Algorithm
potentials	I-Algorithm
to	O
trigger	O
the	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
have	O
an	O
amplitude	O
that	O
is	O
usually	O
5-20	O
mV	O
and	O
they	O
can	O
last	O
from	O
1	O
ms	O
up	O
to	O
several	O
seconds	O
long	O
.	O
</s>
<s>
In	O
order	O
to	O
quantify	O
the	O
behavior	O
of	O
electrotonic	B-Algorithm
potentials	I-Algorithm
there	O
are	O
two	O
constants	O
that	O
are	O
commonly	O
used	O
:	O
the	O
membrane	O
time	O
constant	O
τ	O
,	O
and	O
the	O
membrane	O
length	O
constant	O
λ	O
.	O
</s>
<s>
The	O
membrane	O
time	O
constant	O
measures	O
the	O
amount	O
of	O
time	O
for	O
an	O
electrotonic	B-Algorithm
potential	I-Algorithm
to	O
passively	O
fall	O
to	O
1/e	O
or	O
37%	O
of	O
its	O
maximum	O
.	O
</s>
<s>
The	O
membrane	O
length	O
constant	O
measures	O
how	O
far	O
it	O
takes	O
for	O
an	O
electrotonic	B-Algorithm
potential	I-Algorithm
to	O
fall	O
to	O
1/e	O
or	O
37%	O
of	O
its	O
amplitude	O
at	O
the	O
place	O
where	O
it	O
began	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
are	O
conducted	O
faster	O
than	O
action	B-Algorithm
potentials	I-Algorithm
,	O
but	O
attenuate	O
rapidly	O
so	O
are	O
unsuitable	O
for	O
long-distance	O
signaling	O
.	O
</s>
<s>
The	O
electrotonic	B-Algorithm
potential	I-Algorithm
travels	O
via	O
electrotonic	B-Algorithm
spread	O
,	O
which	O
amounts	O
to	O
attraction	O
of	O
opposite	O
and	O
repulsion	O
of	O
like-charged	O
ions	O
within	O
the	O
cell	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
can	O
sum	O
spatially	O
or	O
temporally	O
.	O
</s>
<s>
Because	O
the	O
ionic	O
charge	O
enters	O
in	O
one	O
location	O
and	O
dissipates	O
to	O
others	O
,	O
losing	O
intensity	O
as	O
it	O
spreads	O
,	O
electrotonic	B-Algorithm
spread	O
is	O
a	O
graded	O
response	O
.	O
</s>
<s>
It	O
is	O
important	O
to	O
contrast	O
this	O
with	O
the	O
all-or-none	O
law	O
propagation	O
of	O
the	O
action	B-Algorithm
potential	I-Algorithm
down	O
the	O
axon	O
of	O
the	O
neuron	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potential	I-Algorithm
can	O
either	O
increase	O
the	O
membrane	O
potential	O
with	O
positive	O
charge	O
or	O
decrease	O
it	O
with	O
negative	O
charge	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
that	O
increase	O
the	O
membrane	O
potential	O
are	O
called	O
excitatory	O
postsynaptic	O
potentials	O
(	O
EPSPs	O
)	O
.	O
</s>
<s>
This	O
is	O
because	O
they	O
depolarize	O
the	O
membrane	O
,	O
increasing	O
the	O
likelihood	O
of	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
As	O
they	O
sum	O
together	O
they	O
can	O
depolarize	O
the	O
membrane	O
sufficiently	O
to	O
push	O
it	O
above	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
,	O
which	O
will	O
then	O
cause	O
an	O
action	B-Algorithm
potential	I-Algorithm
to	O
occur	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
which	O
decrease	O
the	O
membrane	O
potential	O
are	O
called	O
inhibitory	O
postsynaptic	O
potentials	O
(	O
IPSPs	O
)	O
.	O
</s>
<s>
They	O
hyperpolarize	O
the	O
membrane	O
and	O
make	O
it	O
harder	O
for	O
a	O
cell	O
to	O
have	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
Because	O
of	O
the	O
continuously	O
varying	O
nature	O
of	O
the	O
electrotonic	B-Algorithm
potential	I-Algorithm
versus	O
the	O
binary	O
response	O
of	O
the	O
action	B-Algorithm
potential	I-Algorithm
,	O
this	O
creates	O
implications	O
for	O
how	O
much	O
information	O
can	O
be	O
encoded	O
by	O
each	O
respective	O
potential	O
.	O
</s>
<s>
Electrotonic	B-Algorithm
potentials	I-Algorithm
are	O
able	O
to	O
transfer	O
more	O
information	O
within	O
a	O
given	O
time	O
period	O
than	O
action	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
This	O
difference	O
in	O
information	O
rates	O
can	O
be	O
up	O
to	O
almost	O
an	O
order	O
of	O
magnitude	O
greater	O
for	O
electrotonic	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
Ribbon	O
synapses	O
are	O
a	O
type	O
of	O
synapse	O
often	O
found	O
in	O
sensory	O
neurons	O
and	O
are	O
of	O
a	O
unique	O
structure	O
that	O
specially	O
equips	O
them	O
to	O
respond	O
dynamically	O
to	O
inputs	O
from	O
electrotonic	B-Algorithm
potentials	I-Algorithm
.	O
</s>
