Basal ganglia D.Nimer D.Rania Gabr D.Safaa D.Elsherbiny

Objectives Understand the anatomical and functional definition of the basal ganglia. Identify the different components of the basal ganglia. Describe the connections of the different components of the basal ganglia and the indirect pathways from the basal ganglia to the lower motor neurons. Describe signs and symptoms of lesions which affect different components of the basal ganglia.

Basal Ganglia Definition: A group of nuclei, located deep within the cerebral hemispheres. They are part of the extrapyramidal motor system, which are involved in the control of posture and movements (primarily by inhibiting motor functions). But have NO direct input or output connections with spinal cord.

Components: They are composed of: Corpus Striatum: formed of: Caudate nucleus. Lentiform nucleus. Amygdaloid nucleus: Functionally, it is a part of the limbic system. Claustrum: N.B. Subthalmic nucleus and Substantia Nigra: are functionally related to the basal ganglia.

Basal Ganglia

BASAL GANGLIA BASAL GANGLIA CORPUS STRIATUM NEOSTRIATUM CAUDATE NUCLEUS PUTAMEN PALEOSTRIATUM GLOBUS PALLIDUS LENTIFORM NUCLEUS AMYGDALA CLAUSTRUM

Basal Ganglia: Organization Functionally The putamen is more closely allied to caudate nucleus and together constitute the neostriatum or STRIATUM. The globus pallidus is the oldest part of corpus striatum and is called paleostriatum or PALLIDUM. Anatomically the putamen and globus pallidus are together called the lentiform nucleus.

1. CAUDATE NUCLEUS Shape: is a C-shaped nucleus. Parts: Head , body and tail Head: It forms the lateral wall of the anterior horn of the lateral ventricle It is separated from the lentiform nucleus by the anterior limb of the internal capsule.

Body: It lies in the floor of the central part of the lateral ventricle Tail: Extends into the temporal lobe in the roof of the inferior horn of the lateral ventricle. It ends anteriorly at the amygdaloid nucleus.

Relations of Caudate Nucleus to lateral ventricle

LENTIFORM NUCLEUS Shape: Wedge-shaped. Its apex is directed medially. Parts: It is divided into two parts: Putamen: is the lateral part. Globus pallidus: is the medial part.

Relations: Medially: Related to the internal capsule. Anterior limb separates it from caudate nucleus. Posterior limb separates it from the thalamus. Laterally: Related to the external capsule, which separates it from the claustrum. Inferiorly: Related to the amygdaloid nucleus and the anterior commissure.

separating it from the lentiform nucleus. Extreme capsule: 3. CLAUSTRUM Relations: deep to the insula External capsule: separating it from the lentiform nucleus. Extreme capsule: separating it from the insula. 4. AMYGDALOID NUCLEUS It lies in the anterior part of the temporal lobe in the roof and in front of the tip of the inferior horn of the lateral ventricle. Function: It is a part of the limbic and olfactory systems.

Functions of the basal ganglia Part of extra-pyramidal motor system Facilitate behavior & movement – required and appropriate Inhibit unwanted & inappropriate The deficits tend to fall into one of two categories: 1- The presence of extraneous unwanted movements OR 2- An absence or difficulty with intended movements. The balance between the cerebellum and the basal ganglia allows smooth, coordinated movement, and a disturbance in either system will show up as movement disorders.

Basal Ganglia-Summary Dysfunction Disorders of the basal nuclei: Are of two types: Hyperkinetic disorders are those in which there are excessive and abnormal movements (chorea, athetosis, and ballism). Hypokinetic disorders are those in which there is a lack or slowness of movement. Parkinson disease includes both types of motor disturbances.

Diseases of basal ganglia Change in muscle tone Abnormal involuntary movement Parkinsonism Effect on the opposite side Degeneration of dopamine-producing cells in substantia nigra-depletion of dopamine in striatum Resting tremors Rigidity – simultaneous contraction of flexors and extensors Bradykinesia = Slowness of movement – brake cannot be released No paralysis, sensory loss, ataxia