Detailed Chapter Summary
Chapter 15, The Brain and Cranial Nerves
15.1 Overview of the Brain (p. 399)
The adult brain weighs 1,450 to 1,600 g. It is divided into the
In brain anatomy, the directional term
refers to structures relatively close to the forehead, or
anterior to another structure, whereas
refers to more posterior structures, closer to the rear of the
head or closer to the spinal cord.
The cerebrum is conspicuously divided into right and left
separated by a deep
The two hemispheres are joined by a bridge, the
bottom of this fissure. The corpus callosum constitutes a prominent
-shaped landmark in median
sections of the brain.
The cerebellum, the second largest part of the brain, lies inferior to the cerebrum in the posterior
The cerebrum and cerebellum are conspicuously marked by surface
The brainstem is a vertical stalk composed of the
diencephalon, midbrain, pons,
from rostral to caudal; many authorities, however, consider only the last three of these to be
the brainstem. The brainstem is continuous caudally with the spinal cord.
Like the spinal cord, the brain is composed of two kinds of nervous tissue:
. Gray matter constitutes the surface
of the cerebrum and cerebellum,
and nuclei of the brainstem.
White matter lies deep to the cortex and consists of
The brain is surrounded by a the same three meninges as the spinal cord: dura mater, arachnoid
mater, and pia mater. The dura mater is divided into two layers,
some places are separated by blood-filled
. In some places, the dura folds inward to
separate major brain regions, such as the
that separates the two cerebral hemispheres, the
between the cerebrum and cerebellum, and the
between the right and
left halves of the cerebellum. A
separates some areas of dura from the arachnoid, and a
separates arachnoid from pia.