BIOL 251—Anatomy & Physiology I
Chapter 12—The Central Nervous System
I. The Brain (pp. 430–453; Figs. 12.1–12.4; Table 12.1)
A. Embryonic Development (pp. 430–431; Figs. 12.1–12.4)
At three weeks’ gestation, the ectoderm forms the neural plate, which
invaginates, forming the neural groove, flanked on either side by neural folds.
By the fourth week of pregnancy, the neural groove fuses, giving rise to the
neural tube, which rapidly differentiates into the CNS.
The neural tube develops constrictions that divide the three primary brain
vesicles: the prosencephalon (forebrain), mesencephalon (midbrain), and
B. Regions and Organization (p. 431)
The basic pattern of the CNS consists of a central cavity surrounded by a gray
matter core, external to which is white matter.
In the brain, the cerebrum and cerebellum have an outer gray matter layer, which
is reduced to scattered gray matter nuclei in the spinal cord.
C. Ventricles (pp. 431–433; Fig. 12.5)
The ventricles of the brain are continuous with one another, and with the central
canal of the spinal cord. They are lined with ependymal cells, and are filled with
a. The paired lateral ventricles lie deep within each cerebral hemisphere, and are
separated by the septum pellucidum.
b. The third ventricle lies within the diencephalon, and communicates with the
lateral ventricles via two interventricular foramina.
c. The fourth ventricle lies in the hindbrain and communicates with the third
ventricle via the cerebral aqueduct.
D. Cerebral Hemispheres (pp. 433–441; Figs. 12.6–12.11; Table 12.1)
1. The cerebral hemispheres form the superior part of the brain, and are
characterized by ridges and grooves called gyri and sulci.
2. The cerebral hemispheres are separated along the midline by the longitudinal
fissure, and are separated from the cerebellum along the transverse cerebral
3. The five lobes of the brain separated by specific sulci are: frontal, parietal,
temporal, occipital, and insular.
4. The cerebral cortex is the location of the conscious mind, allowing us to
communicate, remember, and understand.
5. The cerebral cortex has several motor areas located in the frontal lobes, which
control voluntary movement.
a. The primary motor cortex allows conscious control of skilled voluntary
movement of skeletal muscles.
b. The premotor cortex is the region controlling learned motor skills.