Basal Ganglia.

BASAL GANGLIA
  • Basal ganglia are the scattered masses of gray matter submerged in subcortical substance of cerebral hemisphere.
  • Basal ganglia form the part of extra pyramidal system, which is concerned with motor activities.
COMPONENTS OF BASAL GANGLIA
  • Basal ganglia include three primary components:
1. Corpus striatum
2. Substantia nigra
3. Subthalamic nucleus of Luys.
  • Corpus striatum is incompletely divided into two parts by internal capsule:
  1. Caudate nucleus
  2.  Lenticular nucleus.
  • Lenticular Nucleus:A vertical plate of white matter called external medullary lamina, divides lenticular nucleus into two portions:
  1. Outer putamen
  2. Inner globus pallidus.
FUNCTIONS OF BASAL GANGLIA
1. CONTROL OF MUSCLE TONE Basal ganglia decrease the muscle tone by inhibiting gamma motor neurons through descending inhibitory reticular system in brainstem. During the lesion of basal ganglia, muscle tone increases leading to rigidity.
2. CONTROL OF MOTOR ACTIVITY
  • Regulation of Voluntary Movements
  • Regulation of Conscious Movements
  •  Regulation of Subconscious Movements
3. CONTROL OF REFLEX MUSCULAR ACTIVITY
4. CONTROL OF AUTOMATIC ASSOCIATED MOVEMENTS
5. ROLE IN AROUSAL MECHANISM
  • Globus pallidus and red nucleus are involved in arousal mechanism because of their connections with reticular formation.
6. ROLE OF NEUROTRANSMITTERS IN THE FUNCTIONS OF BASAL GANGLIA
  1. Dopamine released by dopaminergic fibers from substantia nigra to corpus striatum (putamen and caudate nucleus: dopaminergic nigrostriatal fibers): deficiency of dopamine leads to parkinsonism 
  2. Gammaaminobutyric acid (GABA) secreted by intrinsic fibers of corpus striatum and substantia nigra
  3.  Acetylcholine released by fibers from cerebral cortex to caudate nucleus and putamen
  4. Substance P released by fibers from globus pallidus reaching substantia nigra
  5. Enkephalins released by fibers from globus pallidus reaching substantia nigra
  6. Noradrenaline secreted by fibers between basal ganglia and reticular formation
  7. Glutamic acid secreted by fibers from subthalamic nucleus to globus pallidus and substantia nigra.The highest density of glutamate receptors in basal ganglia are found in Putamen.
  • Among these neurotransmitters, dopamine and GABA are inhibitory neurotransmitters.
DISORDERS OF BASAL GANGLIA
  1. Parkinsom's Disease
  2. Wilson's Disease
  3. Chorea is due to the lesion in caudate nucleus and putamen.
  4. Athetosis because of the lesion in caudate nucleus and putamen.
  5. Choreoathetosis.
  6. Huntington Chorea:Huntington disease is an inherited progressive neural disorder due to the degeneration of neurons secreting GABA in corpus striatum and substantia nigra.
  7. Hemiballismus occurs due to degeneration of subthalamic nucleus. 8.Kernicterus
  8. Obsessive compulsive disorder (OCD) is likely to involve an overactive caudate. On the other hand, an underactive caudate may be involved in various disorders, such as ADD, depression, aspects of schizophrenia, and just plain lethargy.
  9. 10.Tourette's syndrome : Due to involvement of Putamen.
CAUSES OF BASAL GANGLIA CALCIFICATION
  • Endocrinal :Hypo & Pseudo hypo-parathyroidism,(Albright's syndrome),Secondary hyperparathyroidism -Hypothyroidism
  • Toxic : Hypoxia (Birth anoxia) ,Carbonmonoxide/Lead poisoning
  • Chemo/RadioTherapy
  • Infection :TORCH (toxoplasma, congenital rubella, cytomegalo virus, Herpes simplex) HIV - Cysticercosis- TB
  • Metabolic: Fahr's ds, Cockayne's syndrome, mitochondrial disorder (Cytopathy)
  • Vascular malformation: Mineralizing micro angiography
  • Tumor
Exam Question of:
  • Most common site of intracranial hemorrhage in hypertensive hemorrhage is Basal Ganglia.
  • Basal ganglia is involved primarily in Planning and programming of voluntary movements.
  • The highest density of glutamate receptors in basal ganglia are found in Putamen.
  • Subthalamic nucleus of basal ganglia is primarily glutaminergic.
  • Area of brain involved in OCD is Basal Ganglia.
  • Causes of Basal Ganglia Calcification:
  • Endocrinal :Hypo & Pseudo hypo-parathyroidism,(Albright's syndrome),Secondary hyperparathyroidism -Hypothyroidism
  • Toxic : Hypoxia (Birth anoxia) ,Carbonmonoxide/Lead poisoning
  • Chemo/RadioTherapy
  • Infection :TORCH (toxoplasma, congenital rubella, cytomegalo virus, Herpes simplex) HIV - Cysticercosis- TB
  • Metabolic: Fahr's ds, Cockayne's syndrome, mitochondrial disorder (Cytopathy)
  • Vascular malformation: Mineralizing micro angiography
  • Tumor
  • A decorticate rigidity is made by removing the whole cerebral cortex but leaving the basal ganglia intact.
  • The basal ganglia function from thalamus is con­trolled by Anterior Nucleus.
  • Component's of Basal Ganglia: 1. Corpus striatum {i. Caudate nucleus ii. Lenticular nucleus.(a. Outer putamen b. Inner globus pallidus.)}2. Substantia nigra 3. Subthalamic nucleus of Luys.
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