- The largest portion of the brain is the cerebrum.
- Cerebrum consists of two large, hemispheres (the left and the right cerebral hemispheres).
- A deep median longitudinal fissure, called a longitudinal cerebral fissure, partly separates two cerebral hemispheres.
- Both hemispheres are connected by the corpus callosum.
- The cerebral hemisphere’s surface is convoluted, consisting of a sequence of gyri (elevations), spaced by sulci (small depressions), and fissures (deep grooves).
- Each cerebral hemisphere is made up of an inner core of white matter (cerebral medulla) and a surface layer of grey matter known as the cerebral cortex.
- Large masses of grey matter, known as basal nuclei/ganglia are found in the basal part of white matter.
Basal nuclei/ganglia
- These are large masses of grey matter located within the white core of each cerebral hemisphere.
- Basal ganglia consist of –
- Corpus striatum
- Claustrum
- Amygdaloid body
Corpus Striatum
- It is present at the lateral side of thalamus.
- It is divided into a lentiform nucleus (lenticular nucleus) and a caudate nucleus by the internal capsule (a band of nerve fibres).
- Medial part of lentiform nucleus is called as globus pallidus and lateral part is called as putamen.
- Outer to lentiform nucleus, a band of nerve fibres is present called as External capsule.
Claustrum
- Itis a thin concave mass of grey matter present outer to External capsule.
Amygdaloid body
- It is an almond-shaped mass of grey matter called as Amygdaloid body is present in the temporal lobe.
Functions of Basal ganglia
- They are involved in controlling movements during voluntary motor activities.
- Control reflex muscular activity.
- control muscle tone for specific body movements.
- Inhibit unwanted muscular activity.
