July 10, 2011
The brain,
considered the main control tower of the body has three levels; the forebrain, the
midbrain, and the hindbrain. Within these
three levels, are the five processing centers called divisions; these divisions
have specific functions that control the entire body. The forebrain houses the telencephalon and
the diencephalon, the midbrain the mesencephalon, and the hindbrain includes
the metencephalon and the myelencephalon.
The journey through the brain begins with the telencephalon, at the top
or superior of the brain traveling toward the ventral most posterior division,
the myelencephalon.
Within the
forebrain is located the telencephalon, controlling the most complex functions
of the body, it is also the largest division of the brain. Commonly referred to as the cerebral cortex,
this division is segregated anterior to posterior by the longitudinal fissure
into two hemispheres; left and right. The
hemispheres remain connected by the cerebral commissures; the largest along the
longitudinal fissure is called the corpus callosum. The neocortex section of the cerebral cortex
is multi-layered and contains different cells that play an important part in
connecting information relays throughout this newest development of the
cortex. In contrast the hippocampus, at
the medial edge of the cerebral cortex in the medial temporal lobe, is not
neocortex, and has only three major layers. The cerebral cortex is further divided into
four lobes by the central and lateral fissure; frontal, parietal, temporal, and
occipital lobes. The cortex also has
four gyri spaced throughout the lobes, caused by the folds of the cortex; they
are the precentral, postcentral, superior temporal, and cingulate gyri. General functions of these lobes are memory,
motor function, and complex cognitive functions. The telencephalon “initiates voluntary
movement, interprets sensory input [e.g. touch, hearing, and sight], and
mediates complex processes such as learning, speaking, and problem solving”
(Pinel, 2009, pp. 67-68). Another
structure in the telencephalon is the limbic system; the emotional control
center (e.g. love, laughter, and happiness).
It contains the limbic ring and includes the amygdala, hippocampus,
cingulate cortex, fornix, septum, and mammillary body. The final structure is the basal ganglia. Important to motor functions, the basal
ganglia structure contains the amygdala, striatum, both caudate and putamen,
and the globus pallidus. Deterioration
of the basal ganglia is known to play a part in Parkinson’s disease and other
muscle movement disorders (p. 72).
Medial the four
lobes of the telencephalon, or cerebral cortex, lay the diencephalon. This second division of the brain is composed
of two distinct structures; the hypothalamus, which controls the regulation of
hormones, superior to the hypothalamus, is a two lobed structure, the thalamus. The thalamus sends signals to the cerebral cortex
through its many pairs of nuclei. These nuclei
process, transmit, and receive information to and from the appropriate areas of
the sensory cortex; (e.g. visual, auditory, and somatosensory systems). Surrounding the thalamus is the limbic system,
which is involved in the regulations of motivated behaviors: fight or flight,
and basic needs such as eating and sex.
The mesencephalon,
also known as midbrain, consists of two divisions the tectum and the
tegmentum. The tectum is the dorsal
section of the mesencephalon and is composed of two pairs of bumps: the
superior colliculi and the inferior colliculi.
The superior colliculi organizes optical functions and the inferior
colliculi controls audial functions. The
second division of the mesencephalon is the tegmentum. According to Pinel (2009), ventral of
inferior colliculi, the tegmentum contains three structures that
biopsychologists are interested in: the periaqueductal gray the substantia
nigra, and the red nucleus. The
periaqueductal or gray matter that surrounds the cerebral aqueduct plays a role
in regulating pain, the substantia nigra and red nucleus are both components to
sensorimotor systems; both sensory and motor abilities.
To the dorsal end
of the hindbrain lies the metencephalon.
Consisting of two bulges, the first sits on the brain stem’s ventral
surface, called the pons, and the second sits on the dorsal surface of the
brain stem and is called the cerebellum.
Fibers connect the pons and the cerebellum. The pons connected to both the brain stem and
the cerebellum acts as a relay station for body functions and is important to
consciousness, sleep, and sensorimotor functions. The cerebellum, also known as the little brain
is a sensorimotor structure. The
cerebellum is involved in coordination, voluntary motor movement, balance,
equilibrium, and movement. The fifth and
final division of the brain is the myelencephalon. Also known as the medulla oblongata it is inferior
to the pons and anterior to the cerebellum; the lowest or hindmost part of the
brain. The medulla carries signals from
the rest of the brain to the body. The
medial myelencephalon houses the reticular formation; a complex network of
nuclei, responsible for various functions such as arousal, sleep, attention,
movement, and muscle tone. Pinel (2009)
also indicates that the reticular formation “controls various cardiac,
circulatory, and respiratory reflexes” (p. 66). The reticular formation is the medial section
that runs the length of the hindbrain through the dorsal division of the
tegmentum in the midbrain.
The brain is a
complex organ that receives and transmits signals to the rest of the body so
that everything works together to maintain a healthy, functioning
individual. With three sections
consisting of five divisions, each has many intricate functions that interlink
to allow the body to move, think, feel, and experience many sensations that
life has to offer. Whether a division
has only a few medial parts or many intricate structures that intertwine, the
brain tells the body what it needs; food, thought, pain mediation, or muscular
control. The brain is an organ that
should be respected and protected as even a small amount of damage could have
major ramifications on health or body function.
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