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The Anatomy of the Human Brain
The Brain is the most intricate structure in the known universe.
It dictates a plethora of bodily
actions; processing sensory information; modifying biochemical
processes; coordinating movementand of course, providing us the
ability of higher thought/perception. There are three primary
areas
of the human brain:
The rhombencephalon
The midbrain
The forebrain
Hindbrain
The hindbrain is made up of the brain stem and cerebellum and
controls a great variety of actions. It
is positioned in the cranial cavity.
One key form that makes up the hindbrain is the medulla
oblongata. The medulla oblongata is
connected to the spine and is so crucial to life that pathogens
disturbing it are often fatal.
Another important area is the cerebellum. This region is
sometimes called the little brain. It looks
different to the rest of the brain. It has a surface of densely
folded gray matter. It is mainly involved
with movement.
The Pons measures approximately 3cm long and lies next to the
Mid-brain and the lower part of thebrain stem (medulla). It
contains nuclei that have a role with sleep, respiration,
swallowing, bladder
control, hearing, equilibrium, taste, eye movement, facial
expressions, facial sensation, and posture.
Midbrain
The Midbrain/Mesencephalon is superior to the Pons and below the
cerebral hemispheres. The rear
structure of the midbrain is known as the tectum, it is involved
in reflexes relating to auditory
processes and visual processes (e.g. the eye movement, pupil
size, lens shape). The ventral portion
of the midbrain is known as the tegmentum, it is an elaborate
interconnected network of nerves in
charge of unconscious homeostatic and reflexive pathways.
Prosencephalon
The Forebrain is above both the rhombencephalon and the midbrain
as well as being the most
ventral. It has significant roles in the following actions:
Mastication
Directs sensory impulses through the body
Equilibrium
Vision
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Eye movement
Facial sensation
Hearing
Phonation
Intelligence
Memory
Personality
Respiration
Salivation
Swallowing
Smell
Taste
The rhombencephalon is split into 2 fundamental structures:
Telencephalon
The cerebral cortexis the folded outer structure of the brain,
in humans it is between just less than
half a cm thick. It has the highest levels of non- insulated
grey matter of any section of the brain. The
cortex forms folded bulges (thus significantly expanding the
part without increasing the volume)
called gyri; so much so that more than 2 thirds of the brain lie
in these crevices (known as sucli).
The Frontal lobe is the most forward region of the lobes and is
additionally superior to the temporal
lobe. This structure of the brain is related with some of of the
the most central traits associated with
personality (e.g ability to know future results of actions),
learning, impulse control, and prioritising
actions. It is host to most of the brains dopamine receptors
(these are the significant feedback
through which learning is waged).
The temporal lobes are inferior to the frontal and parietal lobe
and anterior to the occipital lobe.
Studies suggest they are the fundamental area of the brain
involved in declarative memory; damage
to the temporal lobes can result in an inability to form memory
after the point of damage
(anterograde amnesia). They contain the hippocampus (long-term
memory) and are concernedhearing and higher visual perception (e.g.
facial recognition).
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The parietal lobe is ahead of the occipital lobe, behind the
frontal lobe and above of the temporal
lobes. The border between the frontal lobe and the parietal lobe
is marked by the central sulcus. The
border between the occipital lobe and the parietal lobe is
marked by the parieto-occipito sulcus and
the border between the temporal lobe and the parietal lobe is
marked by the lateral sulcus. The
parietal lobe coordinates information from multiple senses in
order to establish spatial orientation.
The Occipital lobe is the most posterior of all the main lobes
of the brain. Anatomically this part
contains most of the visual cortex (Brodmann area 17) and damage
to the occipital lobes results in
crucial homonomous vision loss (i.e. the effect is the same in
both eyes). The occipital lobes are
where shape, colour, and like the temporal lobes, facial
recognition take place. Projections from the
occipital lobe to the superior temporal-parietal area are major
for perceiving motion of objects.
The basal ganglia are a region of the corpus striatum and are in
essentially a set of interconnected
nuclei within the brain. Nervous impulses from the cerebral
cortex pass to the basal ganglia where it
is processed and then sent back through the thalamus. There are
a great deal of connections and
pathways within and although the basal ganglia have long been
known to be involved in movement;
it is known this is not there only function, though the exact
process in relation to behaviour control
have yet to be properly established. Evidence suggests that
during learning, basal ganglia and medial
temporal lobe memory systems are activated simultaneously and
that in some learning situations
competitive interference exists between these two systems. One
theory suggests the basal ganglia
decides which out of a number of possible actions the cortex may
be planning, actually gets
executed. Fitting this with idea that dopamine is used as a
reward system for learning.
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