Cerebrospinal fluid

Cerebrospinal fluid (CSF) is a watery liquid similar in composition to blood plasma. It is
formed in the choroid plexuses and circulates through the ventricles into the subarachnoid
space, where it is returned to the dural venous sinuses by the arachnoid villi. The prime
purpose of the CSF is to support and cushion the brain and help nourish it.  Figure 2–4
illustrates the flow of CSF through the central nervous system.

Major regions of the brain and their functions

The major regions of the brain (Figure 2–5) are the  cerebral hemispheres,  diencephalon,
brain stem and cerebellum

Cerebral hemispheres

The cerebral hemispheres (Figure 2–6), located on the most superior part of the brain, are
separated by the longitudinal fissure. They make up approximately 83% of total brain mass,
and are collectively referred to as the cerebrum. The cerebral cortex constitutes a 2-4 mm
thick grey matter surface layer and, because of its many convolutions, accounts for about
40% of total brain mass. It is responsible for conscious behaviour and contains three
different functional areas: the motor areas,  sensory areas and association areas. Located
internally are the white matter, responsible for communication between cerebral areas and
between the cerebral cortex and lower regions of the CNS, as well as the basal nuclei (or
basal ganglia), involved in controlling muscular movement.
Diencephalon
The  diencephalon is located centrally within the forebrain. It consists of the  thalamus,
hypothalamus and  epithalamus, which together enclose the third ventricle. The thalamus
acts as a grouping and relay station for sensory inputs ascending to the sensory cortex and
association areas. It also mediates motor activities, cortical arousal and memories. The
hypothalamus, by controlling the autonomic (involuntary) nervous system, is responsible
for maintaining the body’s homeostatic balance. Moreover it forms a part of the  limbic
system, the ‘emotional’ brain. The epithalamus consists of the pineal gland and the CSF-
producing choroid plexus.

Tweet