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Chapter 13
The Central Nervous System
I. The Central Nervous System (p. 373, Fig. 13.1)
A. The CNS is composed of the brain and spinal cord.
B. Directional terms unique to the CNS are rostral and caudal.
II. The Spinal Cord (pp. 373–378, Figs. 13.2–13.6, 13.34–13.36, and Tables 13.6–13.7)
A. The spinal cord extends from the foramen magnum to L1 or L2 inferiorly. The three major functions of the
spinal cord are: it provides a two-way conduction pathway for signals between the body and brain; it is a major
reflex center; and it is the site of attachment for spinal nerves. (p. 373)
B. The gross anatomy of the spinal cord includes several physical characteristics, including the filum terminals,
conus medullaris, cervical and lumbar enlargements, and the cauda equina. (pp. 373–374)
C. Spinal cord segments refer to the region of the spinal cord from which the fibers of a given spinal nerve
emerge. (p. 375, Fig. 13.3)
D. White matter is composed of myelinated axons and it forms the outer regions of the spinal cord. Tracts of white
matter are classified according to the direction in which they run: ascending, descending, or commissural. (p.
375)
E. Gray matter of the spinal cord is composed of neuronal cell bodies, neuroglia, short unmyelinated axons, and
dendrites. Gray matter forms the H-shaped central region of the spinal cord. Gray matter is arranged into
functionally related groups based on the innervation of somatic or visceral regions of the body. (pp. 375–377,
Figs. 13.4–13.5)
F. Three separate layers of meninges protect the spinal cord: the dura mater, arachnoid mater, and the pia mater.
Cerebrospinal fluid fills the subarachnoid space and the ventricles of the brain and spinal cord. (pp. 377–378,
Fig. 13.6)
III. The Brain (pp. 378–420, Figs. 13.7–13.38, and Tables 13.1–13.5)
A. The human brain along with the spinal cord comprises the CNS; brain functions direct voluntary and
involuntary movements, integration of sensory input, consciousness, and cognitive functions. (p. 378)
B. The embryonic brain develops from the rostral end of the neural tube; by week 5, the three primary brain
vesicles have become the five secondary vesicles; identify the adult structural derivatives and the adult
derivatives of the embryonic neural canal. (pp. 379–380, Figs. 13.7–13.8)
C. A favored classification scheme for the brain includes four parts: the cerebrum (or cerebral hemispheres), the
diencephalon, the brain stem (midbrain, pons, and medulla), and the cerebellum. (pp. 379–380)
D. Names and locations of ventricles of the brain are as follows: paired lateral ventricles in the cerebral
hemispheres, third ventricle in the diencephalon, cerebral aqueduct in the midbrain, and fourth ventricle in the
hindbrain. (pp. 380–382, Fig. 13.11)
E. The brain stem is the most caudal of the four major brain regions. Its primary functions are to produce
programmed automatic behaviors, provide a passageway for fiber tracts running between the cerebrum and
spinal cord, and provide innervation of the face and head through cranial nerves III–XII. There are three
regions of the brain stem. (pp. 382–387, Figs. 13.9–14.1, and Tables 13.1 and 13.5)
1. The medulla oblongata is attached to the five most inferior pairs of cranial nerves, is reticular in formation,
and contains the cardiac, respiratory, and vasomotor centers.
2. The pons forms a “bridge” between the brain stem and cerebellum. Cranial nerves V–VII attach to the pons
and the middle cerebellar peduncles carry information between the cerebral cortex and cerebellum.
3. The midbrain is the most rostral of the three parts of the brain stem. Cell bodies of cranial nerves III and IV
are located in the midbrain. Periaqueductal gray matter initiate the “fight-or-flight response” and the corpora
quadrigemina are brain nuclei involved in visual and auditory reflexes.
F. The cerebellum is the brain’s second largest region. Its functions are smoothing and coordinating body
movements and maintaining posture and equilibrium. (pp. 387–389, Figs. 13.15–13.16, and Table 13.2)
1. Major components of the cerebellum are the anterior, posterior, and flocculonodular lobes, vermis, folia,
cortex, cerebellar peduncles, and arbor vitae (white matter of the cerebellum).
2. The cerebellum receives information on equilibrium, current movements of limbs, neck and trunk, and
information from the cerebral cortex. All fibers to and from the cerebellum are ipsilateral.
G. The diencephalon forms the central core of the forebrain and is surrounded by the cerebral hemispheres. The
components of the diencephalon are the thalamus, hypothalamus, and epithalamus. (pp. 389–393, Figs.
13.16–13.19, and Table 13.3)
1. The thalamus is a relay station for sensory information ascending to primary sensory areas of the cerebral
cortex; the thalamus is the “gateway” to the cerebral cortex.
2. The hypothalamus is the main visceral control center of the body and regulates many activities of visceral
organs including control of the ANS.
3. The epithalamus is the pineal gland, which secretes melatonin.
H. The cerebrum is the most rostral portion of the brain, comprising 83% of the brain’s mass. Gross anatomical
features of the cerebrum include the lobes, gyri, sulci, and fissures. (pp. 393–405, Figs. 13.20–13.27, and
Tables 13.4–13.5)
1. The cerebral cortex is the location of the “conscious mind” and is made of gray matter and composed
primarily of neuronal cell bodies and dendrites. The cerebral cortex is arranged into functionally distinct
areas: the motor areas, sensory areas, and multimodal association areas. Lateralization of cortical
functioning is exhibited by 90–95% of the human population; the left cerebral hemisphere has control
over logic, whereas the right hemisphere is more involved with emotion and artistic and musical skills.
(pp. 393–401, Figs. 13.20–13.25)
2. Myelinated fibers of the cerebral white matter are organized into tracts, which are classified as
commissural, projection, or association tracts. Corpus callosum, internal capsule, and corona radiata are
examples of cerebral white matter. (p. 401, Figs. 13.26–13.27)
3. Deep gray matter of the cerebrum consists of the basal ganglia (motor control), basal forebrain nuclei
(formation of memory), and claustrum. (pp. 401–403, 405, Figs. 13.26–13.27)
I. Functional brain systems are networks of neurons that work together and span large distances in the brain.
The two functional brain systems are the limbic system and the reticular formation. (pp. 405–406, Figs.
13.28–13.29, and Table 13.5)
1. The limbic system is known as the “emotional brain”; a group of structures on the medial aspect of the
cerebral hemispheres and the diencephalon.
2. The reticular formation has branching axons that project to the thalamus, cerebellum, and spinal cord,
which make it ideal for governing the arousal of the brain as a whole.
J. Physical protection of the brain is provided by skull bones, the continuation of meninges surrounding the
spinal cord, and by cerebrospinal fluid. The blood-brain barrier protects the brain from most harmful toxins.
(pp. 408–410, Figs. 13.30–13.32)
1. The skull provides a bony housing for the delicate brain.
2. The dura mater, arachnoid mater, and pia mater surround the brain, but with several significant
modifications to the dura mater to accommodate venous blood drainage and CSF reabsorption.
K. Sensory and motor pathways in the CNS connect the brain and spinal cord to the rest of the body. (pp. 410–
416, Figs. 13.34–13.36, and Tables 13.6–13.7)
1. Ascending pathways conduct general sensory impulses superiorly through chains of two or three neurons
to specific brain regions.
2. Descending pathways transport motor instructions from the brain to the spinal cord.
IV. Disorders of the Central Nervous System (pp. 416–419)
A. Many disorders affect the brain; examples of brain disorders are traumatic brain injuries, such as concussion
and contusion, and degenerative brain diseases, including cerebrovascular accidents (strokes) and Alzheimer’s
disease. (pp. 416–419, Fig. 13.37)
B. Disorders of the spinal cord are paralysis and parathesia. (p. 419)
V. The Central Nervous System Throughout Life (pp. 419–420)
A. Embryonic development and congenital birth defects that involve the brain are anencephaly, spina bifida, and
cerebral palsy. (pp. 419–420, Fig. 13.38)
B. Postnatal changes in the brain represent many neuronal connections during childhood that are based on early
experiences; brain growth stops in early adulthood, and cognitive functions decrease with age.
SUPPLEMENTAL STUDENT MATERIALS to Human Anatomy,
Fifth Edition
Chapter 13: The Central Nervous System
To the Student
This chapter most likely will be one of the most challenging and intriguing ones you will deal with in your study of
human anatomy. Much is known about the structure and function of the brain and spinal cord. But, so much is
unknown that many scientists consider the brain a final frontier in the study of neuroanatomy. It is amazing that the
most highly organized structure known to man does not understand itself. Only the future will answer questions about
memory, senility, and mental illness. Approach your study with a clear understanding of the overall organization of the
nervous system and the details and concepts presented to you in Chapter 13 will be easier to understand.
Step 1: Describe the spinal cord.
- Describe the gross anatomy of the spinal cord, including location, enlargements, and conus medullaris.
- Summarize functions of the spinal cord.
- Describe the meningeal coverings of the spinal cord and indicate the differences from cranial meninges.
- Distinguish between the epidural space, subdural space, and subarachnoid space.
- Distinguish between dorsal sensory roots and ventral motor roots.
- Describe the organization of the white matter of the spinal cord.
- Distinguish between ascending tracts (sensory pathways) and descending tracts (motor pathways) of the spinal
cord.
Step 2: Describe the embryological development, basic parts, organization,
and protection of the brain.
- Summarize basic functions of the brain and describe its consistency and weight.
- Define rostral and caudal.
- Draw a diagram with labels representing the primary brain vesicles of the neural tube dividing into secondary
brain vesicles followed by differentiation into adult structures. Refer to Figure 13.2 for help.
Step 3: Describe the basic parts and organization of the brain.
- Devise a quick reference vocabulary list of all the bold terms and key terms, adding to it as your study progresses.
- Classify the brain parts according to the system used by your textbook.
- Explain the organization of the white matter and gray matter of the brain stem and compare it to that of the matter
in the cerebrum and cerebellum.
- Explain the ventricles of the brain as adult neural canal regions, including specific locations.
- Describe the gross anatomy of the cerebral hemispheres, including sulci, gyri, fissures, and lobes.
- Identify specific functions of the cerebral cortex as well as structural (Brodmann) areas.
- List three functional areas of the cerebral cortex.
- Identify specific functional areas for (1) recognizing objects, (2) spatial relationships, and (3) language.
- Define somatotopy and give examples, including “homunculus.”
- Describe pyramidal tracts.
- Distinguish left cerebral hemisphere specialization from right hemisphere specialization.
- Distinguish between commissural tracts, association tracts, and projection tracts in the white matter.
- Distinguish between the caudate, lentiform, and amygdala basal nuclei of gray matter.
- Name the three parts of the diencephalon and describe the basic function, location, and any associated structural
details for each part.
- Name the three parts of the brain stem and describe the basic function, location, and any associated structural
details for each part.
- Describe the structure and function of the cerebellum.
- Explain the functional brain systems: limbic system and reticular formation.
Step 4: Describe the protective structures associated with the brain.
- Name four structures that protect the brain.
- Describe the three meninges, including the dural extensions.
- Describe cerebrospinal fluid (CSF), including formation and circulation pattern.
- Describe the blood-brain barrier.
Step 5: Describe sensory and motor pathways in the CNS.
- Describe each of the ascending spinal tracts and their functions.
- Describe each of the descending spinal tracts and their functions.
Step 6: Describe disorders of the CNS.
- Distinguish among spinal cord injuries based upon level of injury to the spinal cord.
- Distinguish between contusion and concussion.
- Describe what happens to cause a stroke and the potential results of stroke.
- Describe the progress of Alzheimer’s disease.
Step 7: Describe the CNS throughout life.
- List several birth defects that involve the brain and spinal cord.
- Discuss the formation of neuronal connections during early childhood.
- List results of normal aging to the CNS.