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13f compnents of basal ganglia - Coggle Diagram
13f
compnents of basal ganglia
According to anatomic definition,
basal ganglia are subcortical nuclear
masses which include
corpus striatum
(amygdaloid body and claustrum).
They are so named, as they develop in the basal part of cerebral hemisphere. However, from the physiological viewpoint, the term basal
ganglia include:
Corpus striatum,
Subthalamic nucleus (body of Luys) and
Substantia nigra.
Corpus striatum
Corpus striatum comprises
subcortical masses of grey matter,
which are situated in the
white core of each cerebral hemisphere.
It is divided almost completely by the fibres of internal capsule into two parts:
Caudate nucleus
(medial part)
Lenticular nucleus
(lateral part)
Putamen
(outer part)
Globus pallidus
(inner part)
Phylogenetically and functionally,
the corpus striatum can be divided
into two parts:
Neostriatum or striatum.
Phylogenetically, the caudate nucleus and
putamen are of more recent origin and hence called neostriatum or striatum in short.
Functionally and structurally also, the caudate
nucleus and putamen are similar.
The striatum is divided into:
Dorsal striatum
Ventral striatum
Paleostriatum
refers to globus pallidus,
which is an older and primitive part.
It is also called pallidum, as it is pale (pallid). Pallidum is subdivided into:
Dorsal pallidum
Ventral pallidum
Salient Features of Nuclei of Corpus Striatum
Caudate nucleus.
It is a highly curved,
comma-shaped band of grey matter.
It consists of head, body and a tail.
Caudate nucleus is separated from the lentiform nucleus almost completely by the fibres of internal capsule, except lower part of its
head where it is continuous with putamen nucleus (part of lentiform nucleus).
This area of continuity is known as fundus striati.
The tail of caudate nucleus ends by becoming continuous with putamen
and lies in close relation to the amygdaloid body.
Lenticular nucleus.
It is shaped like a biconvex lens
and is triangular in both coronal and horizontal sections.
It is divided into 2 parts by an
external lamina of white matter:
Putamen
is the outer part of lentiform nucleus.
It is dark in colour
and is roughly quadrilateral.
Globus pallidus
is the inner small part
which is paler in appearance.
It is further divided by an
internal lamina of white matter into:
External segment (GPe)
Internal segment (GPi)
Subthalamic nucleus
Subthalamic nucleus (body of Luys)
is a biconvex mass of grey matter,
which is situated lateral to red nucleus
and dorsal to substantia nigra in
the mesencephalon.
Subthalamic nucleus is separated from
the ventral nuclei of thalamus by
a thin sheet of grey matter
known as zona inserta.
Substantia nigra
Substantia nigra is a sheet made up of
small unpigmented and large pigmented nerve cells.
It appears dark in unstained sections as neurons
within it contain the pigment neuromelanin.
It extends along the entire length of midbrain.
Its cranial end reaches close to the subthalamic
nucleus.
Substantia nigra is divided into 2 parts:
Pars compacta
is the dorsal part of substantia nigra.
Pars compacta of the 2 sides are continuous with each other across the ventral tegmentum.
It contains 2 types of neurons:
Dopaminergic neurons constitute about 75% and
Cholinergic neurons are about 25%.
Pars reticularis
is the ventral part of substantia nigra.
Superiorly, it becomes continuous with the globus pallidus.
Most of the neurons in the pars reticularis are
GABA-ergic.
The striatum has 4 types of neurons;
95% are Gabanergic medium
spiny neurons,
and remaining 5% striatal neurons are nonspiny, which include:
large (cholinergic),
medium (somatostatinergic) and
small (Gabanergic)