<s>
Peripheral	B-Algorithm
chemoreceptors	I-Algorithm
(	O
of	O
the	O
carotid	O
and	O
aortic	O
bodies	O
)	O
are	O
so	O
named	O
because	O
they	O
are	O
sensory	B-Architecture
extensions	O
of	O
the	O
peripheral	O
nervous	O
system	O
into	O
blood	O
vessels	O
where	O
they	O
detect	O
changes	O
in	O
chemical	O
concentrations	O
.	O
</s>
<s>
As	O
transducers	B-Algorithm
of	O
patterns	O
of	O
variability	O
in	O
the	O
surrounding	O
environment	O
,	O
carotid	O
and	O
aortic	O
bodies	O
count	O
as	O
chemosensors	O
in	O
a	O
similar	O
way	O
as	O
taste	O
buds	O
and	O
photoreceptors	O
.	O
</s>
<s>
Taste	O
buds	O
,	O
olfactory	O
bulbs	O
,	O
photoreceptors	O
,	O
and	O
other	O
receptors	O
associated	O
with	O
the	O
five	O
traditional	O
sensory	B-Architecture
modalities	O
,	O
by	O
contrast	O
,	O
are	O
exteroceptors	O
in	O
that	O
they	O
respond	O
to	O
stimuli	O
outside	O
the	O
body	O
.	O
</s>
<s>
As	O
for	O
their	O
particular	O
function	O
,	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
help	O
maintain	O
homeostasis	O
in	O
the	O
cardiorespiratory	O
system	O
by	O
monitoring	O
concentrations	O
of	O
blood	O
borne	O
chemicals	O
.	O
</s>
<s>
Hypoxia	O
and	O
hypercapnia	O
are	O
the	O
most	O
heavily	O
studied	O
and	O
understood	O
conditions	O
detected	O
by	O
the	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
.	O
</s>
<s>
Both	O
carotid	O
bodies	O
and	O
aortic	O
bodies	O
increase	O
sensory	B-Architecture
discharge	O
during	O
hypoxia	O
.	O
</s>
<s>
Carotid	O
bodies	O
are	O
considered	O
the	O
primary	O
peripheral	B-Algorithm
chemoreceptor	I-Algorithm
and	O
have	O
been	O
shown	O
to	O
contribute	O
more	O
to	O
a	O
hypoxic	O
response	O
.	O
</s>
<s>
However	O
,	O
in	O
the	O
chronic	O
absence	O
of	O
the	O
carotid	O
body	O
,	O
the	O
aortic	O
body	O
is	O
able	O
to	O
perform	O
a	O
similar	O
respiratory	O
regulatory	O
role	O
,	O
suggesting	O
that	O
it	O
possesses	O
efficacious	O
mechanisms	O
of	O
signal	O
transduction	B-Algorithm
as	O
well	O
.	O
</s>
<s>
Each	O
of	O
these	O
bodies	O
is	O
composed	O
of	O
a	O
similar	O
collection	O
of	O
cells	O
,	O
and	O
it	O
is	O
the	O
post-transduction	O
signal	O
processing	O
that	O
differentiates	O
their	O
responses	O
.	O
</s>
<s>
Each	O
of	O
these	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
is	O
composed	O
of	O
type	O
I	O
glomus	O
cells	O
and	O
glia-like	O
type	O
II	O
cells	O
.	O
</s>
<s>
Type	O
I	O
cells	O
are	O
densely	O
packed	O
with	O
vesicles	O
containing	O
various	O
neurotransmitters	O
,	O
including	O
dopamine	O
,	O
ATP	O
,	O
serotonin	O
,	O
catecholamine	O
,	O
released	O
during	O
transduction	B-Algorithm
.	O
</s>
<s>
Sensitivity	O
and	O
physiology	O
of	O
the	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
changes	O
throughout	O
the	O
lifespan	O
.	O
</s>
<s>
During	O
this	O
period	O
of	O
development	O
,	O
it	O
is	O
proposed	O
that	O
neonates	O
heavily	O
rely	O
on	O
other	O
oxygen-sensing	O
chemoreceptors	O
,	O
such	O
as	O
the	O
aortic	O
body	O
or	O
central	B-Algorithm
chemoreceptors	I-Algorithm
.	O
</s>
<s>
Increased	O
base	O
rate	O
of	O
ventilation	O
and	O
sensitivity	O
to	O
both	O
hypoxia	O
and	O
hypercapnia	O
occur	O
in	O
pregnant	O
women	O
after	O
gestation	O
week	O
20	O
,	O
and	O
studies	O
suggest	O
this	O
is	O
due	O
at	O
least	O
in	O
part	O
to	O
changes	O
in	O
peripheral	B-Algorithm
chemoreceptor	I-Algorithm
sensitivity	O
.	O
</s>
<s>
However	O
,	O
findings	O
tying	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
to	O
pregnancy-induced	O
variations	O
in	O
breathing	O
could	O
just	O
be	O
correlational	O
,	O
so	O
further	O
studies	O
are	O
needed	O
to	O
identify	O
the	O
cause	O
behind	O
this	O
relation	O
.	O
</s>
<s>
Peripheral	B-Algorithm
chemoreceptors	I-Algorithm
were	O
identified	O
as	O
necessary	O
to	O
breathing	O
regulation	O
much	O
sooner	O
than	O
their	O
mechanisms	O
for	O
acquiring	O
information	O
from	O
the	O
bloodstream	O
were	O
beginning	O
to	O
be	O
understood	O
.	O
</s>
<s>
Both	O
carotid	O
and	O
aortic	O
bodies	O
are	O
composed	O
of	O
type	O
I	O
and	O
type	O
II	O
cells	O
and	O
are	O
believed	O
to	O
transduce	O
signals	O
from	O
blood	O
chemicals	O
in	O
the	O
same	O
way	O
,	O
though	O
post-transduction	O
signal	O
communication	O
may	O
differ	O
.	O
</s>
<s>
Chemosensory	O
transduction	B-Algorithm
in	O
these	O
receptors	O
is	O
still	O
an	O
active	O
area	O
of	O
research	O
,	O
and	O
not	O
all	O
studies	O
agree	O
,	O
but	O
there	O
is	O
growing	O
support	O
for	O
a	O
transduction	B-Algorithm
mechanism	O
dependent	O
upon	O
mitochondrial	O
consumption	O
of	O
oxygen	O
affecting	O
the	O
AMPK	O
enzyme	O
.	O
</s>
<s>
The	O
process	O
of	O
identifying	O
signal	O
transduction	B-Algorithm
in	O
interoceptors	O
such	O
as	O
the	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
requires	O
moving	O
backward	O
from	O
membrane	O
depolarization	O
to	O
discover	O
the	O
previous	O
steps	O
,	O
often	O
internal	O
to	O
the	O
cell	O
,	O
that	O
transduces	O
blood	O
chemicals	O
to	O
a	O
neural	O
signal	O
.	O
</s>
<s>
Some	O
studies	O
propose	O
that	O
heme-oxygenase	O
2	O
is	O
the	O
transducer	B-Algorithm
;	O
however	O
,	O
since	O
its	O
deletion	O
in	O
mice	O
does	O
not	O
affect	O
chemoreceptor	O
oxygen	O
sensitivity	O
,	O
this	O
hypothesis	O
is	O
open	O
to	O
question	O
.	O
</s>
<s>
The	O
difference	O
may	O
actually	O
lie	O
in	O
the	O
cell	O
's	O
metabolism	O
,	O
rather	O
than	O
the	O
AMPK	O
enzyme	O
;	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
display	O
very	O
high	O
background	O
rates	O
of	O
oxygen	O
consumption	O
,	O
supported	O
by	O
its	O
dense	O
network	O
of	O
capillaries	O
.	O
</s>
<s>
In	O
this	O
way	O
,	O
transduction	B-Algorithm
in	O
peripheral	B-Algorithm
chemoreceptor	I-Algorithm
cells	O
is	O
relatively	O
unique	O
.	O
</s>
<s>
Peripheral	B-Algorithm
chemoreceptors	I-Algorithm
are	O
put	O
under	O
stress	O
in	O
a	O
number	O
of	O
situations	O
involving	O
low	O
access	O
to	O
oxygen	O
,	O
including	O
exercise	O
and	O
exposure	O
to	O
high	O
altitude	O
.	O
</s>
<s>
Under	O
sustained	O
hypoxic	O
stress	O
,	O
regardless	O
of	O
the	O
cause	O
,	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
show	O
a	O
great	O
deal	O
of	O
plasticity	O
;	O
they	O
will	O
both	O
swell	O
the	O
size	O
of	O
chemosensing	O
cells	O
and	O
increase	O
their	O
number	O
.	O
</s>
<s>
Though	O
researchers	O
were	O
previously	O
unsure	O
how	O
carotid	O
and	O
aortic	O
bodies	O
came	O
to	O
increase	O
their	O
numbers	O
so	O
rapidly	O
,	O
recent	O
findings	O
point	O
to	O
the	O
type	O
II	O
cells	O
,	O
which	O
were	O
previously	O
thought	O
to	O
have	O
only	O
a	O
supportive	O
role	O
and	O
are	O
now	O
believed	O
to	O
retain	O
properties	O
of	O
stem	O
cells	O
and	O
can	O
differentiate	O
into	O
type	O
I	O
transducer	B-Algorithm
cells	O
.	O
</s>
<s>
Several	O
studies	O
suggest	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
play	O
a	O
role	O
in	O
ventilation	O
during	O
exercise	O
.	O
</s>
<s>
Several	O
studies	O
point	O
to	O
increased	O
circulation	O
of	O
catecholamine	O
or	O
potassium	O
during	O
exercise	O
as	O
a	O
potential	O
effector	O
on	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
;	O
however	O
,	O
the	O
specifics	O
of	O
this	O
effect	O
are	O
not	O
yet	O
understood	O
.	O
</s>
<s>
All	O
suggestions	O
of	O
peripheral	B-Algorithm
chemoreceptor	I-Algorithm
involvement	O
conclude	O
that	O
they	O
are	O
not	O
solely	O
accountable	O
for	O
this	O
response	O
,	O
emphasizing	O
that	O
these	O
receptors	O
are	O
only	O
one	O
in	O
a	O
suite	O
of	O
oxygen-sensing	O
cells	O
that	O
can	O
respond	O
in	O
times	O
of	O
stress	O
.	O
</s>
<s>
In	O
addition	O
to	O
ventilatory	O
effects	O
,	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
may	O
influence	O
neuroendocrine	O
responses	O
to	O
exercise	O
that	O
can	O
influence	O
activities	O
other	O
than	O
ventilation	O
.	O
</s>
<s>
Circulation	O
of	O
the	O
glucose-promoting	O
hormone	O
,	O
glucagon	O
and	O
a	O
neurotransmitter	O
,	O
norepinephrine	O
,	O
is	O
increased	O
in	O
carotid	O
-	O
and	O
aortic-body-enervated	O
dogs	O
,	O
suggesting	O
that	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
respond	O
to	O
low	O
glucose	O
levels	O
in	O
and	O
may	O
respond	O
to	O
other	O
neuroendocrine	O
signals	O
in	O
addition	O
to	O
what	O
is	O
traditionally	O
considered	O
to	O
be	O
their	O
sole	O
role	O
of	O
ventilatory	O
regulation	O
.	O
</s>
<s>
Peripheral	B-Algorithm
chemoreceptors	I-Algorithm
work	O
in	O
concert	O
with	O
central	B-Algorithm
chemoreceptors	I-Algorithm
,	O
which	O
also	O
monitor	O
blood	O
but	O
do	O
it	O
in	O
the	O
cerebrospinal	O
fluid	O
surrounding	O
the	O
brain	O
.	O
</s>
<s>
A	O
high	O
concentration	O
of	O
central	B-Algorithm
chemoreceptors	I-Algorithm
is	O
found	O
in	O
the	O
ventral	O
medulla	O
,	O
the	O
brainstem	O
area	O
that	O
receives	O
input	O
from	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
.	O
</s>
<s>
Taken	O
together	O
,	O
these	O
blood	O
oxygen	O
monitors	O
contribute	O
nerve	O
signals	O
to	O
the	O
vasomotor	O
center	O
of	O
the	O
medulla	O
which	O
can	O
modulate	O
several	O
processes	O
,	O
including	O
breathing	O
,	O
airway	O
resistance	O
,	O
blood	O
pressure	O
,	O
and	O
arousal	O
,	O
with	O
central	O
chemoformation	O
about	O
medullary	O
oxygen	O
levels	O
and	O
peripheral	B-Algorithm
chemoreceptors	I-Algorithm
about	O
arterial	O
oxygen	O
.	O
</s>
