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CHAPTER ELEVEN
Nervous System II
Researchers observe the responses in certain muscles or the
specif c sensations that result. Based on such investigations,
researchers have divided the cerebral cortex into sensory,
association, and motor areas that overlap somewhat.
Sensory Areas
Sensory areas in several lobes oF the cerebrum interpret
impulses From sensory receptors, producing Feelings or sen-
sations. ±or example, the sensations oF temperature, touch,
pressure, and pain in the skin arise in the postcentral gyri oF
the anterior portions oF the parietal lobes along the central sul-
cus and in the posterior wall oF this sulcus
(f g. 11.17)
. The
posterior parts oF the occipital lobes provide vision, whereas
the superior posterior portions oF the temporal lobes contain
the centers For hearing. The sensory areas For taste are near
the bases oF the central sulci along the lateral sulci, and the
sense oF smell arises From centers deep in the cerebrum.
Like motor Fibers, sensory Fibers, such as those in the
fasciculus cuneatus tract,
cross over in the spinal cord or the
brainstem (see f g. 11.12). Thus, the centers in the right central
hemisphere interpret impulses originating From the leFt side
oF the body, and vice versa. However, the sensory areas con-
cerned with vision receive impulses From both eyes, and those
concerned with hearing receive impulses From both ears.
Not all sensory areas are bilateral. The
sensory speech
area,
also called
Wernicke's area,
is in the parietal lobe near
the temporal lobe, just posterior to the lateral sulcus, usu-
ally in the leFt hemisphere (f
g. 11.17). This area receives
and relays input From both the visual cortex and auditory
cortex and is important For understanding written and spo-
ken language.
sensory or motor impulses From the cortex to nerve centers
in the brain or spinal cord.
In a “stroke,” or
cerebrovascular accident
(CVA), a sudden interrup-
tion in blood f
ow in a vessel supplying brain tissues damages the
cerebrum. The aFFected blood vessel may rupture, bleeding into
the brain, or be blocked by a clot. In either case, brain tissues down-
stream From the vascular accident die or permanently lose Function.
Temporary interruption in cerebral blood Flow, perhaps by a clot
that quickly breaks apart, produces a much less serious
transient
ischemic attack
(TIA).
Functions of the Cerebrum
The cerebrum provides higher brain Functions: interpreting
impulses From sense organs, initiating voluntary muscular
movements, storing inFormation as memory, and retrieving
this inFormation in reasoning. The cerebrum is also the seat
oF intelligence and personality.
Functional Regions of the Cortex
The regions oF the cerebral cortex that perForm specif c Func-
tions have been located using a variety oF techniques. ±rom
Science to Technology 2.3, f gure 2E (p. 71), shows how PET
scanning is used to localize particular Functions to specif c
areas oF the cerebral cortex. Clues to cerebral Functioning also
come From people who have suFFered brain disease or injury.
In other studies, areas oF cortices have been exposed
surgically and stimulated mechanically or electrically.
Frontal eye field
Central sulcus
Sensory areas involved with
cutaneous and other senses
Parietal lobe
Sensory speech area
(Wernicke’s area)
Occipital lobe
Combining
visual images,
visual recognition
of objects
Visual area
Cerebellum
Brainstem
Temporal lobe
Interpretation of auditory patterns
Lateral sulcus
Motor speech area
(Broca’s area)
Frontal lobe
Auditory area
Concentration, planning,
problem solving
Motor areas involved with the control
of voluntary muscles
FIGURE 11.17
Some sensory association and motor areas oF the leFt cerebral cortex.
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