Chapter 9a
The Central
Nervous System
About this Chapter
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Anatomy of the central nervous system
The spinal cord
The brain
Brain function
The Embryonic Nervous System
• The neural tube
specializes into the
seven major regions
of the central
nervous system
• A 4-week human
embryo showing the
anterior end of the
neural tube, which
has specialized into
three brain regions
Hindbrain
Forebrain Midbrain
Spinal
cord
Lumen of neural tube
(a)
Figure 9-3a
The Embryonic Nervous System
• At 6 weeks, the
neural tube has
differentiated into
the brain regions
present at birth. The
central cavity
(lumen) shown in
the cross section
will become the
ventricles of the
brain. (see Fig. 9.5)
Hindbrain
Medulla
oblongata
Cerebellum
and Pons
Midbrain
Forebrain
Diencephalon
Cerebrum
Spinal
cord
Cerebrum
Diencephalon
(b)
Eye Midbrain Medulla
oblongata
Figure 9-3b
The Embryonic Nervous System
Cerebrum
• By 11 weeks of
embryonic
development,
the growth of
the cerebrum is
noticeably more
rapid than that
of the other
divisions of the
brain.
Diencephalon
Midbrain
Cerebellum
Pons
Medulla
oblongata
Spinal
cord
(c)
Figure 9-3c
Early
Developmental
Regions
Late Developmental
Regions
Structure Derived
from Regions
Thalamus
Encephalons Development
CNS: Bone and Connective Tissue
• Brain is encased in bony skull or cranium
• Spinal cord runs through vertebral column
• Meninges lies between bone and tissues
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•
Dura mater
Arachnoid membrane
Pia mater
Meningeal layers of the brain cushion and
protect delicate neural tissue
Anatomy of the Central Nervous System
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
SECTIONAL VIEWS OF THE CNS
Cranium
Cranium
Dura mater
Cerebral
hemispheres
Venous sinus
Arachnoid
membrane
Pia mater
Cerebellum
Brain
Subdural
space
Cervical spinal
nerves
Subarachnoid
space
(b) Meningeal layers of the brain cushion and protect delicate neural tissue.
Central canal
Gray matter
White matter
Thoracic spinal
nerves
Spinal
nerve
Spinal
cord
Sectioned
vertebrae
Body of
vertebra
Pia mater
Arachnoid
membrane
Dura mater
Meninges
Autonomic
ganglion
Lumbar spinal
nerves
Sacral spinal
nerves
Coccygeal
nerve
Spinal
nerve
(c) Posterior view of spinal cord and vertebra
(a) Posterior view
Figure 9-4
CNS: Gray and White Matter
• Gray matter
• Unmyelinated nerve cell bodies
• Dendrites
• Axon terminals
• White matter
• Myelinated axons
• Contains very few cell bodies
CNS: Gray and White Matter
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
Central canal
Gray matter
White matter
Thoracic spinal
nerves
Spinal
nerve
Spinal
cord
Sectioned
vertebrae Body of
vertebra
Lumbar spinal
nerves
Sacral spinal
nerves
Coccygeal
nerve
(a) Posterior view
Pia mater
Arachnoid
membrane
Dura mater
Meninges
Autonomic
ganglion
Spinal
nerve
(c) Posterior view of spinal cord and vertebra
Figure 9-4 (2 of 2)
CNS: Gray and White Matter
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
Central canal
Gray matter
White matter
Spinal
nerve
Spinal
cord
Pia mater
Arachnoid Meninges
membrane
Dura mater
Body of
vertebra
Autonomic
ganglion
Spinal
nerve
(c) Posterior view of spinal cord and vertebra
Figure 9-4c
CNS: Bone and Connective Tissue
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
Cranium
Cerebral
hemispheres
Dural Sinses
• drain CSF
• only between dura
SECTIONAL VIEWS OF THE CNS
Cranium
Dura mater
Venous sinus
Arachnoid
membrane
Pia mater
Cerebellum
Brain
Cervical spinal
nerves
Subdural Subarachnoid
space
space
(b) Meningeal layers of the brain cushion and
protect delicate neural tissue.
Figure 9-4 (1 of 2)
CNS: Bone and Connective Tissue
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
SECTIONAL VIEWS OF THE CNS
Cranium
Dura mater
Venous sinus
Arachnoid
membrane
Pia mater
Brain
Subdural Subarachnoid
space
space
(b) Meningeal layers of the brain cushion
and protect delicate neural tissue.
Figure 9-4b
CNS: Ventricles of the Brain
ANATOMY SUMMARY
VENTRICLES OF THE BRAIN
Cerebrum
Lateral ventricles
Third ventricle
Fourth ventricle
Cerebellum
Central canal
Spinal cord
(a)
Lateral view
Frontal view
Figure 9-5a
CNS: Cerebrospinal Fluid
ANATOMY SUMMARY
CEREBROSPINAL FLUID CIRCULATION
Cerebrospinal fluid
Arachnoid
villi
Bone of skull
Dura mater
Endothelial
lining
Choroid plexus
of third ventricle
Blood in
venous sinus
Pia mater
Cerebral
cortex
Arachnoid
membrane
Pia Subarachnoid Arachnoid
mater
space
membrane
Fluid
movement
Arachnoid
villus
Dura mater
(inner layer)
Subdural
space
(d)
(b)
Sinus
Choroid plexus
of fourth ventricle
Spinal cord
Central canal
Subarachnoid
space
Arachnoid
membrane
Dura mater
Figure 9-5b-d
CNS: Cerebrospinal Fluid
ANATOMY SUMMARY
CEREBROSPINAL FLUID CIRCULATION
Cerebrospinal fluid
Bone of skull
Dura mater
Endothelial
lining
Blood in
venous sinus
Cerebral
cortex
Pia Subarachnoid Arachnoid
mater
space
membrane
(d)
Fluid
movement
Arachnoid
villus
Dura mater
(inner layer)
Subdural
space
Figure 9-5d
CSF Flow
CNS: Blood-Brain Barrier
Astrocyte
(a)
★★
Astrocyte foot processes
secrete paracrines that
promote tight
junction formation.
Tight junction prevents
solute movement
between endothelial cells.
Figure 9-6a
CNS: Blood-Brain Barrier
Figure 9-6b
CNS: Neural Tissue – Metabolic Needs
• Oxygen
• Passes freely across blood-brain barrier
• Brain receives 15% of blood pumped by heart
• Glucose
• Brain responsible for about half of body’s
glucose consumption
• Membrane transporters move glucose from
plasma into the brain interstitial fluid
• Progressive hypoglycemia leads to confusion,
unconsciousness, and death
Spinal Cord: Overview
ANATOMY SUMMARY
CENTRAL NERVOUS SYSTEM
Cranium
Cerebral
hemispheres
Cerebellum
• Central nervous system,
posterior view
Cervical spinal
nerves
Thoracic spinal
nerves
Sectioned
vertebrae
Lumbar spinal
nerves
Sacral spinal
nerves
Coccygeal
nerve
(a) Posterior view
Figure 9-4a
Spinal Cord: Anatomy
• Specialization in the spinal cord
White matter
Gray matter
Dorsal root:
carries sensory
(afferent)
information
to CNS.
(a) One segment of spinal cord,
ventral view, showing its pair of nerves.
Ventral root:
carries motor
(efferent) information
to muscles and
glands.
Figure 9-7a
Spinal Cord: Anatomy
Visceral sensory nuclei
Somatic
sensory
nuclei
Dorsal root
ganglion
Lateral
horn
Dorsal
horn
Ventral
horn
Ventral
root
Autonomic
efferent
nuclei
Somatic
motor nuclei
(b) Gray matter consists of sensory and motor nuclei.
Figure 9-7b
Spinal Cord: Anatomy
• Propriospinal tracts remain within the cord
Figure 9-7c (1 of 2)
Spinal Cord: Anatomy
Figure 9-7c (2 of 2)
Spinal Cord: Integrating Center
Sensory information
goes to the brain
Spinal
cord
Stimulus
Sensory
information
Integrating
center
Interneuron
A spinal reflex initiates
a response without input
from the brain.★
Command to
muscles or
glands
Response
Figure 9-8
Anatomy of the Brain
ANATOMY SUMMARY
ANATOMY OF THE BRAIN
LATERAL VIEW
OF THE CNS
Frontal lobe
Frontal lobe
Cingulate gyrus
Parietal
lobe
Cerebrum
Parietal lobe
Corpus callosum
Thalamus
Occipital lobe
Occipital
lobe
Spinal Temporal
lobe
cord
Pons
Vertebrae
Cerebellum
Medulla oblongata
Temporal
lobe
Cerebellum
Pons
Medulla oblongata
(c) Mid-sagittal view of brain
(b) Lateral view of brain
Thalamus
Cut edge of
ascending
tracts to
cerebrum
(a)
Optic tract
Midbrain
Pons
Cranial
nerves
Frontal
bone
Parietal
bone
Temporal
bone
Cut edges of tracts
leading to cerebellum
Medulla
oblongata
(d) Lateral view
of brain stem
Occipital
bone
(e) The skull
Spinal cord
Figure 9-9
The Brain: The Brain Stem
• Most cranial nerves originate along brain
stem
• Cranial nerves can include sensory fibers,
efferent fibers, or both (mixed nerves)
• Many nuclei are associated with reticular
formation
• Medulla
• Somatosensory and corticospinal tracts in
white matter • Pyramids
The Brain: The Brain Stem
ANATOMY SUMMARY
ANATOMY OF THE BRAIN
Thalamus
Cut edge of
ascending
tracts to
cerebrum
Optic tract
Midbrain
Pons
Cranial
nerves
(d) Lateral view
of brain stem
Cut edges of tracts
leading to cerebellum
Medulla
oblongata
Spinal cord
Figure 9-9d
The Brain: Cerebellum
ANATOMY SUMMARY
ANATOMY OF THE BRAIN
Frontal lobe
Parietal
lobe
Occipital
lobe
Temporal
lobe
Pons
Cerebellum
Medulla oblongata
(b) Lateral view of brain
Figure 9-9b
The Brain: Diencephalon
Thalamus
Epithalamus
Hypothalamus
Thalamus
Hypothalamus
Anterior
pituitary
Pineal
gland
Posterior pituitary
Figure 9-10
The Brain: Hypothalamus
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Activates sympathetic nervous system
Maintains body temperature
Controls body osmolarity
Controls reproductive functions
Controls food intake
Interacts with limbic system to influence behavior
and emotions
• Influences cardiovascular control center in medulla
oblongata
• Secretes trophic hormones that control release
of hormones from anterior pituitary gland
The Brain: Mid-Sagittal View
ANATOMY SUMMARY
ANATOMY OF THE BRAIN
Frontal lobe
Cingulate gyrus
Parietal lobe
Corpus callosum
Thalamus
Occipital lobe
Cerebellum
Temporal
lobe
Pons
Medulla oblongata
(c) Mid-sagittal view of brain
Figure 9-9c
The Brain: Gray Matter of the Cerebrum
Corpus
callosum
Basal
ganglia
Lateral
ventricle
Tracts of
white matter
Tip of lateral
ventricle
Gray matter of
cerebral cortex
Figure 9-11
The Brain: Cell Bodies in the Cerebral Cortex Form
Distinct Layers
Figure 9-12
The Brain: The Limbic System
• Emotion, memory, and learning
Cingulate gyrus
plays a role
in emotion.
Thalamus
Hippocampus is
involved in learning
and memory.
Amygdala is
involved in emotion
and memory.
Figure 9-13