BASAL GANGLIA
1.
The basal ganglia are several groups of nuclei
in each cerebral hemisphere. Two ganglia lateral to the thalamus are the globus
pallidus (closer to thalamus) and the putamen. (closer to the cerebral cortex).
2.
The third basal ganglion is the caudate nucleus.
The globus pallidus and the putamen together called the lentiform
nucleus and the three together known as the corpus striatum.
3.
Near by structures that are functionally linked
to the basal ganglia are the subtantia nigra (midbrain) and the subthalmic
nuclei.
4.
A major function of the basal ganglia is to help
regulate initiation and terminate of movements.
5.
Activity of neurons in the putamen precedes or
anticipates body movements and that in the caudate nucleous occurs prior to eye
movements.
6.
The globus pallidus helps regulate the
muscle tone required for specific body movements. They also control
subconscious contractions of skeletal muscles (e.g., automatic arm swinging
while walking).
7.
Basal ganglia also help intiate and
terminate same cognitive processes (eg, attention,memory,and planning) and may
act with the limbic system to regulate emotional behaviours.
v
Same psychiatric disorders, such as obsessive
compulsive disorder,schizophrenia, and
chronic anxiety, are thought to involve dysfunction of circuits between
the basal ganglia and the limbic system.
v
Damage to the basal ganglia results in
uncontrollable shaking (tremor), muscular rigidity (stiffness), and involuntary
muscle movements. In Parkinson disease, neurons that extend from the substantia
nigra to the putamen and caudate nucleus denerate causing movement disruptions.
THE LIMBIC SYSTEM :-
A ring of structures on the inner border of the cerebrum and
floor of the diencephalon constitute the limbic system .
The main components of limbic system are as follows.
·
The limbic lobe (rim of cerebral cortex
on the medial surface of each hemisphere ) includes the cingulate gyrus
(lies above the corpus collasum), and the parahippocampal gyrus.
·
The hippocampus is a portion of the
parahippocampal gyrus that extends into the floor of the lateral ventricles.
·
The dentate gyrus lies between the
hippocampus and parahippocampal gyrus.
·
The amygdala (almond - shaped) is located
close to the tail of the caudate nucleus.
·
The septal nuclei are located within the
septal area (regions under the corpus callosum and the paraterminal gyrus).
·
The mammillary bodies of the hypothalamus
(two round masses) lie close to the midline near the cerebral peduncles.
·
The anterior and medial nuclei of the thalamus
participate in limbic circuits.
·
The fornix, stria terminalis,stria terminails,
stria medullaris, medial forebrain bundle, and mammilothalamic tract are linked
by bundles of interconnecting myelinated axons.
Functions of limbic system :-
1.
It controls emotional behavior expressed in the
form of joy,sorrow,fear,friendship,fight,liking and disliking,and is also
called “emotional brain.
2.
It controls food habits necessary for the
survival of the individual.
3.
It also controls sex behavior necessary for
survival of the species.
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