Lecture 8,9 Basal Ganglia PDF

Lecture 8,9 Basal Ganglia DR. DOHA AL-AFIFI Objectives At the end of this lecture the student will be able to: Describe the Structure of basal ganglia. Describe disorders result from basal ganglia lesion. Differentiate between parkinsonian and Huntington's disease.  Over view T...

Lecture 8,9 Basal Ganglia DR. DOHA AL-AFIFI Objectives At the end of this lecture the student will be able to: Describe the Structure of basal ganglia. Describe disorders result from basal ganglia lesion. Differentiate between parkinsonian and Huntington's disease.  Over view The term “basal ganglia” refers to the large, strongly interconnected nuclear masses deep within the cerebral hemispheres, diencephalon, and midbrain that have a dual function: In regulating movements: enabling desired movements to occur And simultaneously inhibiting competing, non intended movements from occurring. Anatomical consideration The term basal ganglion is generally related to 5 structure: A- There are large nuclear masses: 1- Caudate 2- Putamen 3- globus Pallidus 4- The subthalamic nucleus (in the diencephalon), 5-The substantia nigra (in the midbrain). Functionally : The basal ganglia are : The corpus striatum (in the cerebral hemisphere), The subthalamic nucleus (in the diencephalon), and the substantia nigra (in the midbrain).  The Corpus Striatum The corpus striatum is subdivided anatomically into the caudate and lentiform nuclei. These two large nuclear masses are deep within the cerebral hemisphere. The caudate nucleus is divided into three parts: head, body, and tail. The head is the largest part. The lentiform nucleus is wedge-shaped and consists of several segments that form the putamen and the globus pallidus. The putamen is in the most lateral position and is located between the external capsule and globus pallidus. The globus pallidus is located between the putamen and the internal capsule and is divided into lateral (outer) and medial (inner) segments. The caudate nucleus and putamen are referred to as the striatum The Striatum The caudate nucleus and putamen are referred to as the striatum Is the largest component of the basal ganglia. Has a striped appearance. The striatum has two masses of grey matter separated by a large tract of white of white matter called the internal capsule. They named these two masses the “caudate” nucleus and “putamen” The Striatum The globus pallidus The globus pallidus is located between the putamen and the internal capsule and is divided into lateral (outer) and medial (inner) segments. The globus pallidus, however, is morphologically and physiologically dissimilar from the rest of the corpus striatum. It is referred to as the pallidum. They have inhibitory effects on their targets. As a result, the corpus striatum consists of the caudate nucleus, the putamen, and the Globus pallidus structurally, but the striatum and pallidum functionally. The substantia nigra Substantia Nigra pars compacta Subthalamic nucleus Function of basal ganglia Motor function Regulation and integration of voluntary motor activity. Regulation and maintenance of muscle tone. Regulation and maintenance of Emotional function as ( fascial expression) and associated movement as ( arm swing). Cognitive Function The basal ganglia appear to be necessary for certain forms of implicit memory tasks. The basal ganglia are involved in selecting and enabling various cognitive, executive or emotional programs that are stored in other cortical areas. Disorder of the basal ganglia The abnormalities associated with malfunctions of the basal ganglia are the result of an imbalance in activity in the direct and indirect pathways as a result of the loss of control normally exerted on the striatum by the substantia nigra or on the pallidum by the striatum and subthalamic nucleus Disorders of basal ganglion Abnormalities of the basal ganglia result in movement disorders, such as Parkinson and Huntington diseases, where voluntary intended movements can occur coincidently with involuntary unintended movements. Parkinsonian disease Huntington's disease Case Study A 63-year-old man has been bothered by the shaking of his hands and generalized body stiffness that have become progressively worse during the past 3 years. He moves slowly and deliberately, shuffling his feet as he walks. His shoulders and trunk stoop forward, and his arms hang at his sides. His face remains masklike with no changes of expression. In both hands, a resting tremor of the pill-rolling type stops only when the patient performs a voluntary movement such as picking up a pencil. Examination reveals a generalized hypertonicity with greatly increased resistance to passive stretch in all directions. Although the patient moves his limbs infrequently, examination reveals no paralysis or sensory disturbances in any part of the body.