(1) Brain matter. There are two types of matter in the brain: gray matter
and white matter. Gray matter is in the active portion of the brain. Gray matter receives
and stores impulses. Answering impulses originate in the brain's gray matter. Cell
bodies of neurons and neuroglia are in the gray matter. White matter in the brain
carries impulses to and from gray matter. White matter is composed of nerve fibers
(2) Cerebrum. The cerebrum forms the bulk of the brain and is supported
on the brain stem. The cerebrum is divided into two hemispheres. Each hemisphere
controls the activities of the side of the body opposite that hemisphere. Each
hemisphere is further subdivided into four lobes:
(a) Frontal lobe. This lobe is responsible for voluntary motor function
(origin of pyramidal motor system) and higher mental functions such as judgment and
foresight, affect, and personality.
(b) Temporal lobes. These lobes are responsible for hearing, speech
in the dominant hemisphere, vestibular sense, behavior, and emotion.
(c) Parietal lobe. This lobe is responsible for sensory function, sensory
association areas, higher level processing of general sensory modalities, e.g.,
stereognosis -- recognizing the size and shape of objects by the sense of touch.
(d) Occipital lobe. This lobe is responsible for vision.
(3) Cerebellum. The cerebellum is located behind and below the cerebrum.
Its functions include the following:
(a) Awareness of posture, movement, and voluntary muscle
(b) Receipt of relayed tactile, auditory, and visual input; for example,
processing of information obtained by what you see and hear.
Fine motor coordination; for example, writing.
(4) Midbrain. The midbrain is located above the pons, extending from the
pons to the lower part of the diencephalon. The midbrain provides conduction pathways
to and from higher and lower centers. The righting, postural, and audiovisual reflexes
are reflex centers located in the midbrain. The righting reflex helps keep the head right-
side up. Postural reflexes deal with positioning the head in relation to the trunk of the
body. Visual and auditory reflexes cause you to respond by turning your head in the
direction of a loud noise.