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0:00
My name is Brian MacVicar
and I'm going to
talk to you about
the "Control of Cerebral
Blood Vessels by Astrocytes".
0:10
This image shows a view of
astrocytes taken with
a two-photon laser
scanning microscope.
The astrocytes are shown in
green and the blood
vessels in red.
Astrocytes are small
star-shaped cells that
are distributed
throughout the brain
and actually outnumbered
nerve cells.
0:30
It is only in the last
few years that we
have shown that astrocytes
actually, directly
interact with cerebral
blood vessels and can
modulate cerebral blood flow.
The question of how
cerebral blood flow is
regulated is a very old
question in neuroscience.
Over 100 years ago,
Roy and Sherrington,
shown in this picture
in the slide,
published a paper
in which they said,
"the brain possesses
an intrinsic mechanism
which its vascular supply
can be varied locally
in correspondence
with local variations of
functional activity".
This observation was seminal in
describing how
cerebral blood flow
can be modified in response
to the local activity
in nerve cells.
This, of course,
is now the basis
for functional
neuroanatomical techniques
which MRI or PET techniques are
used to map out areas
of brain activity.
1:28
It is very important
that cerebral
blood flow is matched to the
metabolism of the brain tissue,
even though the brain is only
2 percent of bodyweight,
15 percent of the blood
flow goes to the brain.
The oxygen consumption and
glucose consumption are
also extremely high,
20 percent and 50 percent of
the body demands, respectively.
If there is a mismatch of
cerebral blood flow to
the metabolic demand,
it has terrible consequences on
the functioning of the brain.
It was thought that
vascular dementia results
from a decrease in
blood flow that
does not match the
metabolic demands and leads
to synaptic disruption and
cognitive dysfunction.
In ischemic stroke and after
subarachnoid hemorrhage,
there are unexplained decreases
in cerebral blood
flow that causes
secondary effects and lead
to terrible consequences
to patients.
