Download M555 Medical Neuroscience

M555 Medical Neuroscience
Limbic System
The Limbic System is a wide-spread system of interconnected neural structures located
around the border (or “limb”) of the lateral ventricle.
The Limbic System is involved in emotions, memory acquisition/consolidation and behaviors
and physiological responses such as eating and reproduction that have basic survival and
reproductive values. The structures of the limbic system include several regions of cerebral
cortex, nuclei deep to the cortex, the hypothalamus and thalamus as well as the connections
that tie all these neural structures together.
Look for large areas of cerebral cortex associated with the Limbic System.
cingulate gyrus
medial view
of left cerebral hemisphere
with corpus callosum (in black)
parahippocampal gyrus
The medial, inferior temporal lobe is the location of the parahippocampal gyrus.
Most areaes of cerebral coretx have six layers of cells and axons;
the cortex of the parahippocampal gyrus has three layers.
The cortex of the parahippocampal gyrus can be separated into regions of piriform cortex
and entorhinal cortex.
anterior
piriform
piriform cortex
brain
stem
entorhinal cortex
lateral
ventral view of temporal lobe
entorhinal
There are two major centers in the medial, inferior temporal lobe in the parahippocampal gyrus.
You can see them in dissected brains and in the plastic-embedded brains.
amygdaloid complex = a number of nuclei grouped together as the amygdala
The amygdala lies deep to the prirform cortex of the parahippocampal gyrus.
hippocampal complex = a number of structures grouped together as the hippocampus
The hippocampus lies deep to the entorhinal cortex of the parahippocampal gyrus.
anterior
piriform
uncus A
brain
H
stem
entorhinal
lateral
Two MAjor Limbic Pathways
(fornix)
amygdala
hippocampus
amygdala
figure 23-10 (5th) figure 23-15 (6th)
There are two major bundles of axons associated with these structures
- the stria terminalis and the fornix.
They are found near the lateral ventricles. Both follow a curved path - as though they are coming up
and forward from the temporal lobe. First, the smaller stria terminalis.
stria terminalis
A: amygdala
H: hypothalamus
in the diencepalon
below the thalamus
SN: septal nuclei
(in frontal lobe
near the lamina
terminals and
anterior commissure)
Fig 23-20 (5th)
Fig 23-21 (6th)
The stria terminalis contains axons that carry signals from the amygdala (A).
It’s not the only bundle of amygdalar efferents, but it is more easily seen than the
others. Axons in the stria terminalis terminate in the a region of the telencephalon
(septal nuclei) and in the hypothalamus.
fornix
The fornix is larger than the stria terminalis. It is subdivided into several parts.
Like the stria terminalis, the parts of the fornix follow a curved path coming up and forward
from the temporal lobe.
body
crus
body
crus
fimbria
column
column
hippocampus
precommissural anterior
fornix
commissure
Fimbria (near the hippocampus)
Crus (both fimbria come together along midline)
Body of Fornix (“hanging” from septum pellucidum beneath corpus callosum)
Columns of Fornix extending downward toward anterior commissure
and hypothalamus.
Some axons in the columns of the fornix columns go in front of the anterior commissure
to the septal nuclei (SN) and to the ventral part of the striatum (VS). This part of the fornix is called:
the precommissural fornix (smaller)
More axons in the columns of of the fornix go behind the anterior commissure
to the hypothalamus, including the mammillary bodies (MB). This part of the fornix is called:
the postcommissural fornix (larger)
H: hippocampus
Another major connection in the limbic system extends from the mammillary bodies
to the anterior nucleus of the thalamus.
This connection is called the mammillothalamic tract.
The anterior nucleus of the thalamus projects to the cingulate gyrus.
interventricular
foramen
anterior commissure
fornix
body
fornix
column
anterior
nucleus
mammillothalamic
tract
hypothalamus
septum
pellucidum
corpus callosum
hippocampal commissure
Important structures
amygdala
anterior commissure (as a point of reference)
anterior nucleus of thalamus
cingulate gyrus (not labeled on figures)
hippocampus
hypothalamus
mammillothalamic tract
parts of the fornix 9fimbria, crus, body, column)
fornix
body
fornix
column
fornix crus
fimbria
alveus
hippocampus
don’t be concerned with
alveus
hippocampal commissure
interventricular foramen
septum pellucidum
You should also be able to identify these structures.
stria terminalis
stria terminalis
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hypothalamus
figure 23-21 (5th) figure 23-20 (6th)
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