Basal Ganglia PDF

BASAL GANGLIA Dr. Mohammed Omer Alooba Assistant Professor  OBJECTIVES At the end of the lecture, the student should be able to:  Define “basal ganglia” and enumerate its components.  Enumerate parts of “Corpus Striatum” and their impor...

BASAL GANGLIA Dr. Mohammed Omer Alooba Assistant Professor  OBJECTIVES At the end of the lecture, the student should be able to:  Define “basal ganglia” and enumerate its components.  Enumerate parts of “Corpus Striatum” and their important relations.  Describe the structure of Caudate and Lentiform (Putamen & Globus Pallidus) nuclei.  Differentiate between striatum & paleostriatum in term of connections.  State briefly functions & dysfunctions of Corpus Striatum.  BASAL GANGLIA (NUCLEI)  Group of nerve cells deeply situated in cerebral CN hemispheres  Components: LN 1. Caudate Nucleus 2. Lentiform Nucleus: A divided into N Putamen & Globus Pallidus 3. Amygdaloid Nucleus  Caudate & Lentiform nuclei are functionally related to each other & called “Corpus Striatum”:Part of extrapyramidal motor system, principally involved in the control of posture and Amygdaloid Nucleus (part movements (primarily of limbic system) is only by inhibiting motor embryologically related to functions) Corpus Striatum  CORPUS STRIATUM (Nomenclature)  Bands of grey matter pass from lentiform nucleus across the internal capsule to the caudate nucleus, giving the striated appearance hence, the name corpus striatum.  PARTS  LENTIFORM NUCLEUS  SHAPE: three sided, wedge-shaped mass of grey matter, with a convex outer surface and an apex which lies against the genu of the internal capsule (G) G  DIVISION: divided into 1. Larger darker lateral portion called Putamen (P) 2. Smaller, lighter medial portion called Globus Pallidus (g)  Putamen is more closely related to Caudate nucleus (regarding development, function & connections) and together constitute the Neostriatum or Striatum.  Globus Pallidus is the oldest part of corpus striatum and is called Paleostriatum or Pallidum  PUTAMEN  Separated from globus pallidus by a thin sheath of nerve fibers, the Lateral Medullary Lamina  The white matter lateral to putamen is divided, by a sheath of grey matter, the Claustrum into two layers: Insula  External capsule (1) between the putamen and claustrum and 2 1  Extreme capsule (2) between the claustrum and the insula  GLOBUS PALLIDUS  Consists of two divisions, the Lateral & the Medial segments, separated by a thin sheath of nerve fibers, the Medial Medullary lamina.  The medial segment is similar, in terms of cytology and connections with the pars reticulata of substantia nigra  CAUDATE NUCLEUS  SHAPE: C-shaped mass of grey matter  COMPONENTS: head, body & tail Head: -Rounded in shape -Lies anterior to thalamus (in frontal lobe) -Completely separated from the putamen by the internal capsule except rostrally where it is continuous with the putamen  CAUDATE NUCLEUS Body: -Long & narrow -Extends above thalamus (in parietal lobe) Tail: -Long & tapering -Descends into temporal lobe -Continuous with Amygdaloid Nucleus  CORPUS STRIATUM (Important relations) Head of Caudate Nucleus lies:  Anterior to thalamus  Medial to Lentiform & separated from it by anterior limb of internal capsule (A) Lentiform Nucleus:  Lateral to thalamus & A separated from it by P posterior limb of internal capsule (P) STRIATUM (CAUDATE & PUTAMEN) “The input portion of Corpus striatum” Cerebral Cortex G.P. G.P. Thalamus Striatum Lateral Medial (Intralaminar segment segment nuclei) Pars compacta Substantia Nigra Pars Afferents reticulata Efferents  PALEOSTRIATUM (GLOBUS PALLIDUS) “The output portion of corpus striatum: medial segment of G.P. + Pars Reticulata of S.N.” Thalamic fasciculus Thalamus (Ventral lateral, G.P. G.P. Striatum Lateral Medial Ventral anterior, segment segment centromedian) Subthalamic fasciculus Subthalamic Nucleus Afferents Pars reticulata Efferents Substantia Nigra  CORPUS STRIATUM Function  The corpus striatum assists in regulation of voluntary movement and learning of motor skills as they:  Facilitate behavior and movement that are required and appropriate.  Inhibit unwanted or inappropriate movement.  Dysfunction  Its dysfunction does NOT cause: paralysis, sensory loss or ataxia  It leads to: I. Abnormal motor control: emergence of abnormal, involuntary movements (dyskinesias) II. Alteration in muscle tone: hypertonia/hypotonia