Regulation and Integration of the Body
of the cerebral hemispheres causes their surfaces to crease and
(Figure 12.2c), which increases their sur-
face area and allows more neurons to occupy the limited space.
Regions and Organization
Some textbooks discuss brain anatomy in terms of the
(see Figure 12.1c), but in this text, we will consider
the brain in terms of the medical scheme and the four adult
brain regions shown in Figure 12.2c: (1) cerebral hemispheres,
(2) diencephalon, (3) brain stem (midbrain, pons, and medulla
oblongata), and (4) cerebellum.
Te basic pattern of the CNS is a central cavity surrounded
by gray matter (mostly neuron cell bodies), external to which
is white matter (myelinated ﬁber tracts). Te spinal cord ex-
hibits this basic pattern, but the brain has additional regions
of gray matter not present in the spinal cord. Both the cerebral
hemispheres and the cerebellum have an outer layer or “bark”
of gray matter called a cortex. Tis pattern changes with descent
through the brain stem—the cortex disappears, but scattered
gray matter nuclei are seen within the white matter. At the cau-
dal end of the brain stem, the basic pattern is evident. Knowl-
edge of the basic pattern of the CNS will help you explore the
brain, moving from the most rostral region (cerebrum) to the
most caudal (brain stem). But ﬁrst, let’s explore the central hol-
low cavities that lie deep within the brain—the ventricles.
are continuous with one another and with
the central canal of the spinal cord
. Te hollow ven-
tricular chambers are ﬁlled with cerebrospinal ﬂuid and lined by
, a type of neuroglia (see Figure 11.3c on p. 389).
, one deep within each cerebral
hemisphere, are large C-shaped chambers that reﬂect the pat-
tern of cerebral growth. Anteriorly, the lateral ventricles lie close
together, separated only by a thin median membrane called the
sid-um; “transparent wall”). (See
Figure 12.10, p. 440.)
Each lateral ventricle communicates with the narrow
in the diencephalon via a channel called an
Te third ventricle is continuous with the
via the canal-like
that runs through the mid-
brain. Te fourth ventricle lies in the hindbrain dorsal to the
pons and superior medulla. It is continuous with the central ca-
nal of the spinal cord inferiorly. Tree openings mark the walls
of the fourth ventricle: the paired
in its side
walls and the
in its roof. Tese apertures con-
nect the ventricles to the
a ﬂuid-ﬁlled space surrounding the brain.
Check Your Understanding
Which ventricle is surrounded by the diencephalon?
Which two areas of the adult brain have an outside layer
of gray matter in addition to central gray matter and
surrounding white matter?
What is the function of convolutions of the brain?
For answers, see Appendix H.
List the major lobes, ﬁssures, and functional areas of the
Explain lateralization of hemisphere function.
(a) Week 5:
Two major flexures form, causing the telencephalon
and diencephalon to angle toward the brain stem.
(b) Week 13:
Cerebral hemispheres develop and grow
posterolaterally to enclose the diencephalon and the rostral brain
Shows adult pattern of structures and convolutions.
Initially, the cerebral surface is
smooth. Folding begins in month 6, and convolutions become more
obvious as development continues. See-through view in (b) and (c).