Basal ganglia is structure in brain usually at above the level of midbrain

1. BASAL
GANGLIA
Presented by,
DHANUSH K M
4th Year BPT

2. Contents
1. Introduction
2. Anatomy
Components
Connections
Pathways
Functions
3. Parallel circuits in the Basal Ganglia
4. Lesions of the Basal Ganglia
5. Reference

3. Introduction
• The basal ganglia, also known as the basal nuclei, are a group of
subcortical structures found deep within the white matter of the brain,
located at the base of forebrain.
• Basal ganglia are the scattered masses of grey matter submerged in
subcortical substance of cerebral hemi-sphere.
• Basal ganglia form the part of extra pyramidal system, which is
concerned with motor activities.
• These structures play a crucial role in coordinating and fine-tuning
voluntary motor activity and are involved in several higher cortical
functions

4. Basal Ganglia
Amygdala
Corpus Striatum
Neostriatum
(Striatum)
Paleostraitum
( Pallidum )
Caudate Putamen
Globus
pallidas
Lentiform
nucleus

5. Lenticular / Lentiform Nucleus

6. Components of Basal Ganglia
Basal ganglia include three primary components:
1. Corpus striatum
2. Substantia nigra
i. Substantia nigra reticulata (SNr)
ii. Substantia nigra compacta (SNc)
3. Subthalamic nucleus
****** Some evidence suggests that the nucleus accumbens
and the ventral pallidum should also be classified among the
Basal Ganglia ******

7. 1. Corpus striatum
• Corpus striatum is a mass of grey matter situated at the base of
cerebral hemispheres in close relation to thalamus.
• Corpus striatum is incompletely divided into two parts by internal
capsule.
i. Caudate nucleus
ii. Lenticular nucleus

8. a. Caudate Nucleus :
It’s a elongated arched grey mass lying medil to internal capsule, which
surronds the thalamus and it itself surronded by lateral ventricle.
Caudate nucleus has head , body and tail portion.
• Anterior part in front of interventricular foramen is called Head.
• Head gradually and imperceptibility tapers caudally into the body.
• The body is long and narrow, and forms the floor of central part of
lateral ventricle.
• A tail which merges at its anterior extremity with an almond-shaped
mass of grey matter called Amygdaloid body.

9. b. Lentiform nucleus
● Appears triangular in the coronal section
with its tip directed medially.
● Divided by the thin lamina of white matter
known as external medullary lamina into
i. Lateral part- Putamen
ii. Medial part- Globus pallidus

10. Putamen
• The putamen is larger lateral part and consists of densely packed
small cells.
• It is darker in colour, and structurally similar to the caudate nucleus.
Globus pallidus
• The globlus pallidus is smaller medial part. It is lighter in colour and
consists of large (motor) cells. It is also known as pallidumas it
appears pale in section (pallid= pale).
• The globus pallidus is further subdivided into segments by the
internal medullary lamina :
i. Globus pallidus external ( Gpe )
ii. Globus pallidus internal ( Gpi )

11. 2. Substantia nigra
• It’s a large motor nucleus present in the midbrain between the tegmentum
and the basis pedunculi
• It is situated below red nucleus.
• It is made up of large pigmented and small nonpigmented cells. The
pigment contains high quantity of iron.
i. Substantia nigra reticulata (SNr) : ventral cell sparse portion,
functionally related to internal part of globus pallidas. They use the
inhibitory neurotransmitter GABA.
ii. Substantia nigra compacta (SNc) : dorsal cell rich portion. Neurons
here are pigmented because of neuromelanin, these cells contain
dopamine

13. 3. Subthalamic nucleus
• This small nucleus in the ventral part of the diencephalon looks like a
biconvex lens in coronal section.
• It is located caudal to the lateral half of the thalamus and inferomedial
to the globus pallidus.
• It is separated from thalamus by a smaller nucleus, called zona inserta.
• The subthalamic nucleus and globus pallidus are interconnected by the
subthalamic fasciculus which traverses the internal capsule

14. Connections of Basal Ganglia:
Forms three types of extensive connections with cerebral cortex and
thalamus
1. Afferent connections
2. Intermuscular connections
3. Efferent connections

15. 1. Afferent connections :
Afferent terminate in neostraitum are excititory (cholinergic) & includes
a. Cortico-striate projection :-
receives afferent from all parts of cerebral cortex, especially
from frontal & parietal lobes to neostraitum.
b. Thalamo-striate projection :-
receives afferent from intralaminar, mediodorsal, ventralant &
centeromedian nuclei of thalamus to neostriatum.
c. Raphestriate projection :-
receives afferent from dorsal raphe nucleus to striatum.

17. a. Niagrostriatal tract ( dopaminergic ) :-
pars compacta of subthalamic nucleus contains cell body
having (-) Niagrostriatal tract – dopamine & its axons
terminate in neostriatum , i.e, in caudate nucleus and putamen.
b. GABAergic (-) projections –
➡️ the neostriatum projects
-- to pars reticulata of SN.
-- to both segments of GP.
➡️ external segment of GP projects to subthalamic nucleus
c. Subthalamic nucleus projects to internal segment of GP & SN
2. Internuclear connections :

19. 2. Efferent connections :
Are mainly from GP & SN ( GABAergic – inhibitory )
a. From internal segment of GP
to VPL & CM nuclei of thalamus, then to prefrontal & premotor
cortex
b. From pars reticulata of SN
-- to VPL & VA nuclei of thalamus
-- to Superior colliculus & pendunculopontine nucleus
• Projections from GP & SN to thalamus are (-) GABAergic
&
• Thalamic nuclei projections on to motor cortex are (+) cholinergic

21. Functions of Basal Ganglia :
● Concerned with planning and programming of voluntary movements.
● Determine how rapidly a movement is to be performed and how large the
movement must be.
● Decrease muscle tone and inhibit unwanted muscular activity.
● Regulate the muscle tone and thus helps in smoothening the voluntary motor
activities of the body.
● Control automatic associated movements, like swinging of arms during
walking.

22. Neural pathways through Basal Ganglia
1. Direct pathway
2. Indirect pathway
• These pathways are involved in control of motor activities

23. 1. Direct pathway

24. 2. Indirect pathway

25. Applied Physiology – Disorders of Basal ganglia
1. PARKINSON DISEASE
2. WILSON DISEASE
3. CHOREA
4. ATHETOSIS
5. CHOREOATHETOSIS
6. HUNTINGTON CHOREA
7. HEMIBALLISMUS
8. KERNICTERUS

26. Reference
1. Essentials of Medical Physiology - K. Sembulingam and Prema
Sembulingam
2. Pathophysiology of the Motor Systems: Principles and Clinical
Presentations Christopher M. fredericks, lisa k. saladin
3. Textbook of Clinical Neuroanatomy ; 3rd Edition – Vishram Singh
4. Guyton & Hall Textbook of Medical Physiology
5. Comprehensive textbook of medical physiology 3rd edition

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THANK YOU !
the_.dhanush