<s>
Graded	B-Algorithm
potentials	I-Algorithm
are	O
changes	O
in	O
membrane	O
potential	O
that	O
vary	O
in	O
size	O
,	O
as	O
opposed	O
to	O
being	O
all-or-none	O
.	O
</s>
<s>
They	O
include	O
diverse	O
potentials	O
such	O
as	O
receptor	B-Algorithm
potentials	I-Algorithm
,	O
electrotonic	B-Algorithm
potentials	I-Algorithm
,	O
subthreshold	B-Algorithm
membrane	I-Algorithm
potential	I-Algorithm
oscillations	I-Algorithm
,	O
slow-wave	B-Algorithm
potential	I-Algorithm
,	O
pacemaker	B-Algorithm
potentials	I-Algorithm
,	O
and	O
synaptic	O
potentials	O
,	O
which	O
scale	O
with	O
the	O
magnitude	O
of	O
the	O
stimulus	O
.	O
</s>
<s>
They	O
occur	O
at	O
the	O
postsynaptic	O
dendrite	O
in	O
response	O
to	O
presynaptic	O
neuron	O
firing	B-Algorithm
and	O
release	O
of	O
neurotransmitter	O
,	O
or	O
may	O
occur	O
in	O
skeletal	O
,	O
smooth	O
,	O
or	O
cardiac	O
muscle	O
in	O
response	O
to	O
nerve	O
input	O
.	O
</s>
<s>
The	O
magnitude	O
of	O
a	O
graded	B-Algorithm
potential	I-Algorithm
is	O
determined	O
by	O
the	O
strength	O
of	O
the	O
stimulus	O
.	O
</s>
<s>
Graded	B-Algorithm
potentials	I-Algorithm
that	O
make	O
the	O
membrane	O
potential	O
less	O
negative	O
or	O
more	O
positive	O
,	O
thus	O
making	O
the	O
postsynaptic	O
cell	O
more	O
likely	O
to	O
have	O
an	O
action	B-Algorithm
potential	I-Algorithm
,	O
are	O
called	O
excitatory	O
postsynaptic	O
potentials	O
(	O
EPSPs	O
)	O
.	O
</s>
<s>
Depolarizing	O
local	O
potentials	O
sum	O
together	O
,	O
and	O
if	O
the	O
voltage	O
reaches	O
the	O
threshold	B-Algorithm
potential	I-Algorithm
,	O
an	O
action	B-Algorithm
potential	I-Algorithm
occurs	O
in	O
that	O
cell	O
.	O
</s>
<s>
When	O
the	O
presynaptic	O
neuron	O
has	O
an	O
action	B-Algorithm
potential	I-Algorithm
,	O
Ca2+	O
enters	O
the	O
axon	O
terminal	O
via	O
voltage-dependent	O
calcium	O
channels	O
and	O
causes	O
exocytosis	O
of	O
synaptic	O
vesicles	O
,	O
causing	O
neurotransmitter	O
to	O
be	O
released	O
.	O
</s>
<s>
If	O
the	O
EPSP	O
is	O
not	O
large	O
enough	O
to	O
trigger	O
an	O
action	B-Algorithm
potential	I-Algorithm
,	O
the	O
membrane	O
subsequently	O
repolarizes	O
to	O
its	O
resting	O
membrane	O
potential	O
.	O
</s>
<s>
This	O
shows	O
the	O
temporary	O
and	O
reversible	O
nature	O
of	O
graded	B-Algorithm
potentials	I-Algorithm
.	O
</s>
<s>
Graded	B-Algorithm
potentials	I-Algorithm
that	O
make	O
the	O
membrane	O
potential	O
more	O
negative	O
,	O
and	O
make	O
the	O
postsynaptic	O
cell	O
less	O
likely	O
to	O
have	O
an	O
action	B-Algorithm
potential	I-Algorithm
,	O
are	O
called	O
inhibitory	O
post	O
synaptic	O
potentials	O
(	O
IPSPs	O
)	O
.	O
</s>
<s>
The	O
typical	O
neuron	O
has	O
a	O
threshold	B-Algorithm
potential	I-Algorithm
ranging	O
from	O
–	O
40	O
mV	O
to	O
–	O
55	O
mV	O
.	O
</s>
<s>
Temporal	O
summation	O
occurs	O
when	O
graded	B-Algorithm
potentials	I-Algorithm
within	O
the	O
postsynaptic	O
cell	O
occur	O
so	O
rapidly	O
that	O
they	O
build	O
on	O
each	O
other	O
before	O
the	O
previous	O
ones	O
fade	O
.	O
</s>
<s>
An	O
action	B-Algorithm
potential	I-Algorithm
occurs	O
when	O
the	O
summated	O
EPSPs	O
,	O
minus	O
the	O
summated	O
IPSPs	O
,	O
in	O
an	O
area	O
of	O
membrane	O
reach	O
the	O
cell	O
's	O
threshold	B-Algorithm
potential	I-Algorithm
.	O
</s>
