<s>
In	O
electrophysiology	B-Application
,	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
is	O
the	O
critical	O
level	O
to	O
which	O
a	O
membrane	O
potential	O
must	O
be	O
depolarized	O
to	O
initiate	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
In	O
neuroscience	O
,	O
threshold	B-Algorithm
potentials	I-Algorithm
are	O
necessary	O
to	O
regulate	O
and	O
propagate	O
signaling	O
in	O
both	O
the	O
central	O
nervous	O
system	O
(	O
CNS	O
)	O
and	O
the	O
peripheral	O
nervous	O
system	O
(	O
PNS	O
)	O
.	O
</s>
<s>
Most	O
often	O
,	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
is	O
a	O
membrane	O
potential	O
value	O
between	O
–	O
50	O
and	O
–	O
55	O
mV	O
,	O
but	O
can	O
vary	O
based	O
upon	O
several	O
factors	O
.	O
</s>
<s>
Along	O
with	O
reconstructing	O
the	O
action	B-Algorithm
potential	I-Algorithm
in	O
the	O
1950s	O
,	O
Alan	O
Lloyd	O
Hodgkin	O
and	O
Andrew	O
Huxley	O
were	O
also	O
able	O
to	O
experimentally	O
determine	O
the	O
mechanism	O
behind	O
the	O
threshold	O
for	O
excitation	O
.	O
</s>
<s>
Through	O
use	O
of	O
voltage	O
clamp	O
techniques	O
on	O
a	O
squid	O
giant	O
axon	O
,	O
they	O
discovered	O
that	O
excitable	O
tissues	O
generally	O
exhibit	O
the	O
phenomenon	O
that	O
a	O
certain	O
membrane	O
potential	O
must	O
be	O
reached	O
in	O
order	O
to	O
fire	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
Since	O
the	O
experiment	O
yielded	O
results	O
through	O
the	O
observation	O
of	O
ionic	O
conductance	O
changes	O
,	O
Hodgkin	O
and	O
Huxley	O
used	O
these	O
terms	O
to	O
discuss	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
They	O
soon	O
discovered	O
that	O
at	O
threshold	B-Algorithm
potential	I-Algorithm
,	O
the	O
inward	O
and	O
outward	O
currents	O
,	O
of	O
sodium	O
and	O
potassium	O
ions	O
respectively	O
,	O
were	O
exactly	O
equal	O
and	O
opposite	O
.	O
</s>
<s>
As	O
opposed	O
to	O
the	O
resting	O
membrane	O
potential	O
,	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
's	O
conditions	O
exhibited	O
a	O
balance	O
of	O
currents	O
that	O
were	O
unstable	O
.	O
</s>
<s>
The	O
basis	O
is	O
that	O
at	O
a	O
certain	O
level	O
of	O
depolarization	O
,	O
when	O
the	O
currents	O
are	O
equal	O
and	O
opposite	O
in	O
an	O
unstable	O
manner	O
,	O
any	O
further	O
entry	O
of	O
positive	O
charge	O
generates	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
This	O
specific	O
value	O
of	O
depolarization	O
(	O
in	O
mV	O
)	O
is	O
otherwise	O
known	O
as	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
The	O
threshold	O
value	O
controls	O
whether	O
or	O
not	O
the	O
incoming	O
stimuli	O
are	O
sufficient	O
to	O
generate	O
an	O
action	B-Algorithm
potential	I-Algorithm
.	O
</s>
<s>
In	O
that	O
case	O
,	O
subthreshold	B-Algorithm
membrane	I-Algorithm
potential	I-Algorithm
oscillations	I-Algorithm
are	O
observed	O
in	O
some	O
type	O
of	O
neurons	O
.	O
</s>
<s>
The	O
signals	O
can	O
only	O
continue	O
along	O
the	O
neuron	O
to	O
cause	O
an	O
action	B-Algorithm
potential	I-Algorithm
further	O
down	O
if	O
they	O
are	O
strong	O
enough	O
to	O
make	O
it	O
past	O
the	O
cell	O
's	O
membrane	O
resistance	O
and	O
capacitance	O
.	O
</s>
<s>
The	O
threshold	B-Algorithm
potential	I-Algorithm
has	O
also	O
been	O
shown	O
experimentally	O
to	O
adapt	O
to	O
slow	O
changes	O
in	O
input	O
characteristics	O
by	O
regulating	O
sodium	O
channel	O
density	O
as	O
well	O
as	O
inactivating	O
these	O
sodium	O
channels	O
overall	O
.	O
</s>
<s>
The	O
delayed-rectifier	O
potassium	O
channels	O
are	O
responsible	O
for	O
the	O
late	O
outward	O
phase	O
of	O
the	O
action	B-Algorithm
potential	I-Algorithm
,	O
where	O
they	O
open	O
at	O
a	O
different	O
voltage	O
stimulus	O
compared	O
to	O
the	O
quickly	O
activated	O
sodium	O
channels	O
.	O
</s>
<s>
The	O
action	B-Algorithm
potential	I-Algorithm
is	O
recorded	O
downstream	O
from	O
the	O
triggering	O
impulse	O
.	O
</s>
<s>
The	O
stimulus	O
is	O
automatically	O
decreased	O
in	O
steps	O
of	O
a	O
set	O
percentage	O
until	O
the	O
response	O
falls	O
below	O
the	O
target	O
(	O
generation	O
of	O
an	O
action	B-Algorithm
potential	I-Algorithm
)	O
.	O
</s>
<s>
Tracking	O
threshold	O
has	O
advantages	O
over	O
other	O
electrophysiological	B-Application
techniques	O
,	O
like	O
the	O
constant	O
stimulus	O
method	O
.	O
</s>
<s>
Furthermore	O
,	O
it	O
can	O
be	O
used	O
to	O
identify	O
characteristics	O
of	O
significant	O
medical	O
conditions	O
through	O
comparing	O
the	O
effects	O
of	O
those	O
conditions	O
on	O
threshold	B-Algorithm
potential	I-Algorithm
with	O
the	O
effects	O
viewed	O
experimentally	O
.	O
</s>
<s>
The	O
role	O
of	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
has	O
been	O
implicated	O
in	O
a	O
clinical	O
context	O
,	O
namely	O
in	O
the	O
functioning	O
of	O
the	O
nervous	O
system	O
itself	O
as	O
well	O
as	O
in	O
the	O
cardiovascular	O
system	O
.	O
</s>
<s>
With	O
patch	O
clamp	O
recording	O
,	O
an	O
analogous	O
state	O
was	O
replicated	O
in	O
vitro	O
in	O
rat	O
cortical	O
neurons	O
after	O
induction	O
of	O
febrile	O
body	O
temperatures	O
;	O
a	O
notable	O
decrease	O
in	O
threshold	B-Algorithm
potential	I-Algorithm
was	O
observed	O
.	O
</s>
<s>
As	O
ischemia	O
occurs	O
through	O
inhibition	O
of	O
the	O
sodium-potassium	O
pump	O
,	O
abnormalities	O
in	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
are	O
hence	O
implicated	O
.	O
</s>
<s>
When	O
the	O
threshold	O
is	O
reached	O
and	O
the	O
resulting	O
action	B-Algorithm
potential	I-Algorithm
fires	O
,	O
a	O
heartbeat	O
results	O
from	O
the	O
interactions	O
;	O
however	O
,	O
when	O
this	O
heartbeat	O
occurs	O
at	O
an	O
irregular	O
time	O
,	O
a	O
potentially	O
serious	O
condition	O
known	O
as	O
arrythmia	B-Application
may	O
result	O
.	O
</s>
<s>
A	O
variety	O
of	O
drugs	O
can	O
present	O
prolongation	O
of	O
the	O
QT	B-Algorithm
interval	I-Algorithm
as	O
a	O
side	O
effect	O
.	O
</s>
<s>
Prolongation	O
of	O
this	O
interval	O
is	O
a	O
result	O
of	O
a	O
delay	O
in	O
sodium	O
and	O
calcium	O
channel	O
inactivation	O
;	O
without	O
proper	O
channel	O
inactivation	O
,	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
is	O
reached	O
prematurely	O
and	O
thus	O
arrhythmia	B-Application
tends	O
to	O
result	O
.	O
</s>
<s>
These	O
drugs	O
,	O
known	O
as	O
pro-arrhythmic	O
agents	O
,	O
include	O
antimicrobials	O
,	O
antipsychotics	O
,	O
methadone	O
,	O
and	O
,	O
ironically	O
,	O
antiarrhythmic	B-Algorithm
agents	I-Algorithm
.	O
</s>
<s>
The	O
use	O
of	O
such	O
agents	O
is	O
particularly	O
frequent	O
in	O
intensive	O
care	O
units	O
,	O
and	O
special	O
care	O
must	O
be	O
exercised	O
when	O
QT	B-Algorithm
intervals	I-Algorithm
are	O
prolonged	O
in	O
such	O
patients	O
:	O
arrhythmias	B-Application
as	O
a	O
result	O
of	O
prolonged	O
QT	B-Algorithm
intervals	I-Algorithm
include	O
the	O
potentially	O
fatal	O
torsades	B-Algorithm
de	I-Algorithm
pointes	I-Algorithm
,	O
or	O
TdP	O
.	O
</s>
<s>
Diet	O
may	O
be	O
a	O
variable	O
in	O
the	O
risk	O
of	O
arrhythmia	B-Application
.	O
</s>
<s>
Polyunsaturated	O
fatty	O
acids	O
,	O
found	O
in	O
fish	O
oils	O
and	O
several	O
plant	O
oils	O
,	O
serve	O
a	O
role	O
in	O
the	O
prevention	O
of	O
arrhythmias	B-Application
.	O
</s>
<s>
By	O
inhibiting	O
the	O
voltage-dependent	O
sodium	O
current	O
,	O
these	O
oils	O
shift	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
to	O
a	O
more	O
positive	O
value	O
;	O
therefore	O
,	O
an	O
action	B-Algorithm
potential	I-Algorithm
requires	O
increased	O
depolarization	O
.	O
</s>
<s>
Clinically	O
therapeutic	O
use	O
of	O
these	O
extracts	O
remains	O
a	O
subject	O
of	O
research	O
,	O
but	O
a	O
strong	O
correlation	O
is	O
established	O
between	O
regular	O
consumption	O
of	O
fish	O
oil	O
and	O
lower	O
frequency	O
of	O
hospitalization	O
for	O
atrial	O
fibrillation	O
,	O
a	O
severe	O
and	O
increasingly	O
common	O
arrythmia	B-Application
.	O
</s>
