Write a short note on the Forebrain.

(N/A) The forebrain consists of three main regions:
$(i)$ Cerebrum $(ii)$ Thalamus $(iii)$ Hypothalamus.
$(i)$ Cerebrum: It forms the major part of the human brain. $A$ deep cleft divides the cerebrum longitudinally into two halves,which are termed as the left and right cerebral hemispheres.
The hemispheres are connected by a tract of nerve fibres called corpus callosum.
The layer of cells which covers the cerebral hemisphere is called the cerebral cortex and is thrown into prominent folds (Gyri,Sulci,and Fissures).
The cerebral cortex is referred to as the grey matter due to its greyish appearance. The neuron cell bodies are concentrated here,giving it this colour.
The cerebral cortex contains motor areas,sensory areas,and large regions that are neither clearly sensory nor motor in function. These regions are called association areas. They are responsible for complex functions like intersensory associations,memory,and communication.
Fibres of the tracts are covered with the myelin sheath,which constitutes the inner part of the cerebral hemisphere. They give an opaque white appearance to the layer and hence,are called the white matter.
$(ii)$ Thalamus: The cerebrum wraps around a structure called the thalamus. It is a major coordinating centre for sensory and motor signaling.
$(iii)$ Hypothalamus: It lies at the base of the thalamus. It contains a number of centres which control body temperature,and the urge for eating and drinking.
Hypothalamus also contains several groups of neurosecretory cells,which secrete hormones called hypothalamic hormones.
Limbic System: The inner parts of cerebral hemispheres and a group of associated deep structures like amygdala,hippocampus,etc.,form a complex structure called the limbic system.
It is involved in the regulation of sexual behaviour,expression of emotional reactions (e.g.,excitement,pleasure,rage,fear,and motivation).