Page 21 - Handbook of Electronic Assistive Technology

8 HANDBOOK OF ELECTRONIC ASSISTIVE TECHNOLOGY

Central Nervous System

We have a brain that initiates and modifies neuronal signals, which inputs links between areas
and outputs, and a spinal cord that sends messages, down to control movement and up from
a variety of sensory organs to allow us to feel different elements of sensation. This is the CNS.
From here messages pass to and from somatic senses and motor functions via smaller
nerves – the peripheral nervous system.
We also have subconscious control of normal body functions, such as heart rate, blood
pressure and sweating, via the autonomic nervous system, and also ways of controlling
our digestive and bowel habit – the alimentary or enteric nervous system.
By the time we reach 18 years our brain on average weighs 1.275 kg in women and
1.36 kg in men. From that point the integrity of the pathways and cellular matrices starts
to deteriorate; little hope for those of us in the latter stages of our working life.
The brain itself is basically subdivided into three main functional areas.
The forebrain: Sitting on the top, covered by a complex system of folded and convoluted
cellular areas, which as we have previously stated optimises surface area in a limited skull
volume, is the cerebrum. This is partially split into two hemispheres – a left and a right.
Underneath it sits the midbrain – the brain stem – and behind this at the base of the
brain is the hindbrain – the cerebellum.
Each of the hemispheres is then divided into four main lobes (Fig. 1-5) named after
the bones that overlie them rather than any easy area of surface delineation: the frontal,
parietal, temporal and occipital lobes. These have specific roles to play in our senses,
thoughts, words and deeds.
There are also two other specific areas important in consciousness and emotional
response, which are highly developed in most humans and are found at their confluence –
the limbic system and insular cortex.

FIGURE 1-5 Lobes of the brain� Courtesy of Fig. 2 Lobes of the brain. Fuller, G., Manford, M., 2010. Neurology
ebook and Illustrated Coloured Text, third ed. Elsevier.