The Central Nervous System
is implicated in
failure to thrive
, a condition characterized by
delay in growth or development that occurs when a child is de-
prived of a warm, nurturing relationship.
Te most dorsal portion of the diencephalon, the
forms the roof of the third ventricle. Extending from its
posterior border and visible externally is the
e-al; “pine cone shaped”) (see Figures 12.10 and
12.13c). Te pineal gland secretes the hormone
sleep-inducing signal and antioxidant; see Chapter 16) and,
along with hypothalamic nuclei, helps regulate the sleep-wake
forms the caudal border of the
Check Your Understanding
Why is the thalamus called the “gateway to the cerebral cortex”?
The hypothalamus oversees a branch of the peripheral
nervous system. Which branch?
For answers, see Appendix H.
Identify the three major regions of the brain stem, and
note the functions of each area.
From superior to inferior, the brain stem regions are mid-
brain, pons, and medulla oblongata (Figures 12.10, 12.12,
and 12.13). Each roughly an inch long, collectively they ac-
count for only 2.5% of total brain mass. Histologically, the
organization of the brain stem is similar (but not identical)
to that of the spinal cord—deep gray matter surrounded by
white matter ﬁber tracts. However, the brain stem has nuclei
of gray matter embedded in the white matter, a feature not
found in the spinal cord.
Brain stem centers produce the rigidly programmed, auto-
matic behaviors necessary for survival. Positioned between the
cerebrum and the spinal cord, the brain stem also provides a
pathway for ﬁber tracts running between higher and lower neu-
ral centers. Additionally, brain stem nuclei are associated with
10 of the 12 pairs of cranial nerves (which we will describe in
Chapter 13), so it is heavily involved with innervating the head.
is located between the diencephalon and pons
). On its ventral aspect two
klz) form vertical
pillars that seem to hold up the cerebrum, hence their name
meaning “little feet of the cerebrum” (Figure 12.13a, b, and
(“leg of the cerebrum”) of
each peduncle contains a large pyramidal (corticospinal)
motor tract descending toward the spinal cord. Te
(synapse point of
cranial nerve I)
Optic nerve (II)
Inferior view of the brain,
showing the three parts of the brain stem:
midbrain, pons, and medulla oblongata.
a small portion of the midbrain is visible in this
view. (For a related image, see
A Brief Atlas of the
, Figure 49.)