The Central Nervous System
dah-loid), an almond-shaped nucleus that sits on the
tail of the caudate nucleus, and other parts of the rhinencephalon
, the C-shaped
). In the diencephalon, the main
limbic structures are the
(“arch”) and other ﬁber tracts link these limbic
system regions together.
Te limbic system is our
. Te amygdaloid body and the anterior part of the
seem especially important in emotions. Te
amygdaloid body is critical for responding to perceived threats
(such as angry or fearful facial expressions) with fear or aggres-
sion. Te cingulate gyrus plays a role in expressing our emo-
tions through gestures and in resolving mental conﬂicts when
we are frustrated.
Odors oFen trigger emotional reactions and memories.
Tese responses reﬂect the origin of much of the limbic system
in the primitive “smell brain” (rhinencephalon). Our reactions
to odors are rarely neutral (a skunk smells
and repulses us),
and odors oFen recall memories of emotion-laden events.
Extensive connections between the limbic system and lower
and higher brain regions allow the system to integrate and re-
spond to a variety of environmental stimuli. Most limbic sys-
tem output is relayed through the hypothalamus. Because the
hypothalamus is the neural clearinghouse for both autonomic
(visceral) function and emotional response, it is not surprising
that some people under acute or unrelenting emotional stress
fall prey to visceral illnesses, such as high blood pressure and
heartburn. Such emotion-induced illnesses are called
Because the limbic system interacts with the prefrontal lobes,
there is an intimate relationship between our feelings (mediated
Cognitive Functions of the Cerebellum
Neuroanatomy, imaging studies, and observations of patients
with cerebellar injuries suggest that the cerebellum also plays
a role in thinking, language, and emotion. As in the motor sys-
tem, the cerebellum may compare the actual output of these
systems with the expected output and adjust accordingly. Much
still remains to be discovered about the precise role of the cer-
ebellum in nonmotor functions.
Check Your Understanding
In what ways are the cerebellum and the cerebrum similar?
In what ways are they different?
For answers, see Appendix H.
Functional Brain Systems
Locate the limbic system and the reticular formation, and
explain the role of each functional system.
±unctional brain systems are networks of neurons that work
together but span relatively large distances in the brain, so
they cannot be localized to speciﬁc regions. Te
are excellent examples.
summarizes their functions, as well as those of the cerebral
hemispheres, diencephalon, brain stem, and cerebellum.
The Limbic System
is a group of structures located on the medial
aspect of each cerebral hemisphere and diencephalon. Its cerebral
structures encircle (
ring) the upper part of the brain stem
. Te limbic system includes the
of the limbic system
Fiber tracts connecting
limbic system structures
Cerebral structures of
the limbic system
The limbic system.
Lateral view of the brain, showing some of the structures
of the limbic system, the emotional-visceral brain. The brain stem is not illustrated.