Basal Nuclei
Introduction
They lie deep within the cerebral hemispheres there are groups of cell bodies called nuclei (previously called ganglia).
They act as relay stations where impulses are passed from one neurone to the next in a chain.
The important masses of grey matter are :-
Basal nuclei
Thalamus
Hypothalamus
Location And Subdivisions Of Basal Ganglia
Location :
Subcortical, lies deep within the cerebral hemispheres
Consist of the caudate nucleus, putamen, globus pallidus and substantia nigra
The putamen and caudate nucleus along with the interposed anterior limb of the internal capsule are collectively known as the corpus striatum (i.e. striated body) because of their appearance.
Similarly, the shape of the putamen and globus pallidus resembles a lens, and they are collectively called the lenticular nucleus.
(Putamen + caudate nucleus + internal capsule = corpus striatum
Putamen + globus pallidus = lenticular nucleus)
Functions
Basal ganglia : associated with motor and learning functions
It influences the skeletal muscle tone.
Establishes postures.
Monitors and coordinates slow, sustained contractions related to posture and support.
Controls voluntary movements
Selects and maintains purposeful motor activity
Suppresses unwanted or useless movement.
Inhibits muscle tone throughout the body; proper muscle tone is normally maintained through a balance of excitatory and inihibtory inputs to the neurones that innervate skeletal muscle
When the basal nuclei are affected by disease - say in disorders like Huntington disease, Parkinson's disease or Wilson's disease - the person has unwanted movements, such as involuntary jerking movements of an arm or leg or spasmodic movement of facial muscles.
Injury to this area leads to rigidity, hypotonia
In addition the basal ganglion houses the amygdala, which mediates inborn and acquired emotional responses.
Mediates both conscious and unconscious emotional feelings through connections with the prefrontal lobe.
Disorders linked with the basal ganglia
Huntington's disease
Parkinson's disease
Tourette's disorder
Obsessive-compulsive disorder
Attention-deficit hyperactivity disorder (ADHD)
Athymhormic syndrome (PAP syndrome)
Cerebral palsy: basal ganglia damage during second and third trimester of pregnancy
Tardive dyskinesia, caused by chronic antipsychotic treatment
Wilson Disease
(Hepatolenticular Degeneration)
Inheritance of a mutation on chromosome 13.
The mutation prevents the body from eliminating excess copper.
Ceruloplasmin is the protein that binds and removes excess copper and its levels are greatly reduced in this disorder. Too much copper in the system damages the cells of the liver and leads to cirrhosis. Neurological damage primarily occurs in the putamen and globus pallidus.
Symptoms : -
o A peculiar type of tremor in the upper extremities, slowness of movement and changes in temperament.
o Persons may become exceptionally argumentative,
o Overly emotional
o Decrease in mental capabilities.
o Kayser-Fleischer rings (a rusty brown discoloration at the rims of the corneas) as the copper begins to affect the nervous system.
o The disease first affects the liver, and if treatment is administered early enough, damage to the nervous system is dramatically reduced.
Treatment :-
o Elimination of copper containing foods such as chocolate and mushrooms.
o Chelate excess copper and eliminate it from the body.
