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Corpus callosum
VetBooks.ir Thalamus Epithalamus
(pineal gland)

Cerebellum

Olfactory bulb
Diencephalon
Hypothalamus
Pituitary gland Medulla
Midbrain
(mesencephalon) Pons

Figure 10-9. Median (midsagittal) section of the brain.

sensory and motor functions. Anatomic control autonomic and endocrine func-
regions defined by consistent gyri and sulci tions, emotional behaviors, and memory, a
and general function are referred to as fact that accounts for the striking ability of
lobes. The cerebral cortex is the site at odors to affect these functions.
which voluntary movements are initiated,
sensations are brought to consciousness, Diencephalon. The diencephalon derives
and higher functions, such as reasoning from the prosencephalon. The thalamus,
and planning, take place. epithalamus, hypothalamus, and the
The cortices of the two hemispheres are third ventricle are included in the
connected anatomically and functionally diencephalon.
by a massive bundle of axons, the corpus The thalamus is an important relay
callosum. This structure allows the two center for nerve fibers connecting the cer-
halves of the brain to share and integrate ebral hemispheres to the brainstem, cere-
information. bellum, and spinal cord. The epithalamus,
Deep to the cerebral cortex are aggre- dorsal to the thalamus, includes the pineal
gates of subcortical gray matter called the gland, which is an endocrine organ in
basal nuclei (an older term, basal ganglia, mammals. Its primary secretion, mela-
is discouraged, as the word ganglion usually tonin, appears to be important in circadian
refers to an accumulation of cell bodies out- (daily) rhythms and sleep cycles. In addi-
side the CNS). The basal nuclei are impor- tion, activity of the pineal gland is likely to
tant in initiation and maintenance of normal be important in species with seasonal
motor activity. In humans, Sydenham’s reproductive cycles.
chorea and Parkinson’s disease are move- The hypothalamus, ventral to the thal-
ment disorders caused by degeneration amus, surrounds the ventral part of the
of parts of the basal nuclei. Basal nuclear third ventricle and comprises many nuclei
disease is uncommon in animals. that function in autonomic activities and
The rhinencephalon is, from an evolu- behavior. Attached to the ventral part of
tionary standpoint, one of the oldest parts the hypothalamus is the hypophysis, or
of the cerebrum. It comprises a series of pituitary gland, one of the most impor-
ventral and deep cortical structures associ- tant endocrine glands. The neuronal
ated primarily with the sense of smell (olfac- connections between the hypothalamus
tion). The rhinencephalon has prominent and the hypophysis constitute a critical
connections to the parts of the brain that point of integration of the two primary