Chapter 3
Structure of the Nervous
System
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Chapter 3 Outline
• Basic Features of the Nervous System
• The Central Nervous System
• The Peripheral Nervous System
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•
Basic Features of the Nervous System
• Neur_____
• An imaginary line drawn through the center of
the length of the central nervous system, from
the bottom of the spinal cord to the front of the
forebrain.
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•
Basic Features of the Nervous System
• ___________
• With respect to the central nervous system,
located near or toward the head.
• _____________
• With respect to the central nervous system, located
near or toward the tail.
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•
Basic Features of the Nervous System
• ____________
• “Toward the ______”; with respect to the central
nervous system, in a direction along the neuraxis
toward the front of the face.
• ____________
• “Toward the _____”; with respect to the central nervous
system, in a direction along the neuraxis away from
the front of the face.
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Basic Features of the Nervous System
• __________
• “Toward the_____”; with respect to the central
nervous system, in a direction perpendicular
to the neuraxis toward the top of the head or the back.
• ______________
• “Toward the ________”; with respect to the central
nervous system, in a direction perpendicular to
the neuraxis toward the bottom of the skull or the
front surface of the body.
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Basic Features of the Nervous System
• ___________
• Toward the side of the body, away from the _______.
• ___________
• Toward the middle of the body, away from the side.
• _____________
• Located on the same side of the body.
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Basic Features of the Nervous System
• _______________
• Located on _______________ side of the body.
• Cross section or Frontal section
• A transverse cut like a salami.
• With respect to the central nervous system, a slice taken
at right angles to the neuraxis.
• A slice through the brain __________to the forehead.
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Basic Features of the Nervous System
• _____________section
• A slice through the brain parallel to the ground.
• _____________section
• A slice through the brain parallel to the neuraxis and
perpendicular to the ground.
• Midsagittal
• The plane through the neuraxis perpendicular to the
ground; divides the brain into two symmetrical halves.
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•
Basic Features of the Nervous System
• Meninges
• Meninges
• The three layers of tissue that encase the central
nervous system; the dura mater, arachnoid membrane,
and the pia mater.
• ________mater
• The outermost of the meninges; tough and flexible.
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Basic Features of the Nervous System
• Meninges
• Arachnoid membrane
• From the Greek arachne, meaning “spider”.
• The middle layer of the meninges, located between the
dura mater and the inner pia mater.
• _________ mater
• The layer of the meninges adjacent to the surface of the
brain; thin and delicate.
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Basic Features of the Nervous System
• Meninges
• ______________ space
• The fluid-filled space that cushions the brain; located
between the arachnoid membrane and the pia mater.
• _________________ fluid
• A clear fluid, similar to blood plasma, that fills the
ventricular system of the brain and the subarachnoid
space surrounding the brain and spinal cord.
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Dura mater
Arachnoid membrane
Subarachnoid space
[Blood vessels and cerebrospinal fluid (CSF)]
Pia mater
Central nervous system tissue
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Basic Features of the Nervous System
• The ventricular system and production of
cerebrospinal fluid
• ________________ (“little bellies”):
• ________ hollow spaces located inside the brain.
• Each ventricle produces CSF.
• CSF supports the weight of the brain. (The ___ brain
weights about __ ounces when supported by CSF).
• Helps reduce shock to the CNS caused by sudden head
movements.
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Basic Features of the Nervous System
• The ventricular system and production of
cerebrospinal fluid
• The brain contains about 125 ml of CSF
• The half life of CSF is about three hours
• All of the CSF is replaced every six hours by
the_____________________.
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Basic Features of the Nervous System
• The ventricular system and production of
cerebrospinal fluid
• Ventricle
• One of the hollow spaces within the brain filled with
cerebrospinal fluid.
• Lateral ventricle
• One of the two ventricles located in the center of the
telencephalon.
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Basic Features of the Nervous System
• The ventricular system and production of
cerebrospinal fluid
• Third ventricle
• The ventricle located in the center of the diencephalon.
• Cerebral aqueduct
• A narrow tube interconnecting the third and fourth
ventricles of the brain, located in the center of the
mesencephalon.
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Basic Features of the Nervous System
• The ventricular system and production of
cerebrospinal fluid
• Fourth ventricle:
• The ventricle located between the cerebellum and the
dorsal pons, in the center of the metencephalon.
• ________________________:
• The highly vascular tissue that protrudes into the
ventricles and produces cerebrospinal fluid.
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• CSF Reabsorbtion:
• CSF production and reabsorption
must occur at the __________.
• Reabsorbtion occurs in the
subarachnoid space around the
CNS (reabsorbed into the blood).
• Hydrocephalic??
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• Hydrocephalic skull
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The Central Nervous System
• Development of the central nervous system
• Central nervous system development begins ___ days
after conception.
• Neural tube develops by twenty-first day to give rise to
the brain and spinal cord.
• Neural tube closes at day twenty-eight and forms the
ventricles, forebrain, mid brain, and hindbrain.
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• Subdivisions of the brain:
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•
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Forebrain
• ___encephalon (end brain)
• ___encephalon (interbrain)
Midbrain
• ___encephalon
Hindbrain
• ___encephalon (afterbrain)
• __elencephalon (marrowbrain)
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The Central Nervous System
• Development of the central nervous system
• Neural tube
• A hollow tube, closed at the rostral end, that forms from
ectodermal tissue early in embryonic development;
serves as the ______ of the central nervous system.
• Ventricular zone
• A layer of cells that line the inside of the neural tube,
contains _______ cells that divide and give rise to the
central nervous system.
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The Central Nervous System
• Development of the central nervous system
• Cerebral cortex (cortex means “bark”)
• The outmost layer of gray matter of the cerebral
hemispheres that is about 3 mm thick.
• Radial glia
• Special glia with fibers that grow radially outward
from the ventricular zone to the surface of the cortex;
provide ________ for neurons migrating outward during
brain development.
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Cerebral cortex grows from the inside out:
• Neurons _____ along the radial fibers like
_________, pushing past the neurons that were
born earlier.
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The Central Nervous System
• Development of the central nervous system
• Founder cells
• Cells of the ventricular zone that divide and give
rise to cells of the central nervous system.
• _____________ division
• Division of a founder cell that gives rise to two
identical founder cells; increases the size of the
ventricular zone and hence the brain that develops
from it. (This lasts until __ weeks of age.)
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The Central Nervous System
• Development of the central nervous system
• ___________________ division
• Division of a founder cell that gives rise to another
founder cell and a neuron, which migrates away
from the ventricular zone towards its final resting
place in the brain. (7 weeks to 3 months of age: about 1
billion neurons each day migrate along the radial glial
fibers).
• _____________ (literally, a “falling away”)
• Death of a cell caused by a chemical signal that
activates a genetic mechanism inside the cell.
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Survival of the fittest?
• About twice as many neurons are born then can fit
in the available space.
• Neurons _____________for synaptic receptor sites.
• Neurons that fail to form synaptic connects die by
apoptosis.
• General theme: Use it or ________ it!
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Neurogensis:
Old Belief: adult brains do
not display neurogensis.
New Data: stem cells
(founder cells) are found in
olfactory bulb & ____________
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• Neurogensis:
• Exposure to new odors increases
survival rate of new olfactory bulb
neurons.
• Learning tasks enhance
neurogenesis in the hippocampus
(declarative memory tasks)
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• Suppression of neurogenesis:
• Depression and stress depress
neurogenesis in the hippocampus.
• Drugs that reduce stress and
depression reinstate neurogenesis
in the hippocampus.
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• Brain Evolution:
• Chimpanzees and humans share 98.8% of
their genes.
• Corrected for body weight the human brain is
3 times larger than the chimp brain, and 10
times larger the rhesus monkey brain.
• 1-2 or 3-4 more ___________ of symmetrical
founder cells divisions would account for
these brain size differences.
• A simple process could account for huge
differences in brain size.
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The Central Nervous System
• The forebrain-telencephalon
• Forebrain
• The most rostral of the three major divisions
of the brain; includes the telencephalon and
diencephalon.
• Cerebral hemisphere
• One of the two major portions of the forebrain,
covered by the cerebral cortex.
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The Central Nervous System
• The forebrain-telencephalon
• Subcortical region
• The region located within the brain, beneath the
cortical surface.
• Contains the ________ system and the basal ganglia.
• __________
• A groove in the surface of the cerebral hemisphere,
smaller than a fissure.
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The Central Nervous System
• The forebrain-telencephalon
• Fissure
• A major groove in the surface of the brain, larger
than a sulcus.
• Gyrus
• A convolution of the cortex of the cerebral
hemispheres, separated by sulci or fissures.
The fissures and gyri increase the surface area 3-fold.
“Lower mammals” have a ___________surface area to
volume ratio.
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• Axons & cell bodies
• ________matter: myelinated
axons.
• ______matter: cell bodies.
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The Central Nervous System
• The forebrain-telencephalon
• Primary visual cortex
• The region of the posterior ___________ lobe whose
primary input is from the visual system.
• Calcarine fissure
• A fissure located in the occipital lobe on the
medial surface of the brain; most of the primary
visual cortex is located along its upper and lower
banks.
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The Central Nervous System
• The forebrain-telencephalon
• Primary auditory cortex
• The region of the superior __________lobe whose
primary input is from the auditory system.
• Lateral fissure
• The fissure that separates the temporal lobe from
the overlying frontal and parietal lobes.
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The Central Nervous System
• The forebrain-telencephalon
• Primary somatosensory cortex
• The region of the anterior parietal lobe whose
primary input is from the somatosensory system.
• Central sulcus
• The sulcus that separates the frontal lobe from
the parietal lobe.
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The Central Nervous System
• The forebrain-telencephalon
• Primary motor cortex
• The region of the posterior frontal lobe that
contains neurons that control __________ of
skeletal muscle.
• The connections of this region are _____________.
• The left primary motor cortex controls the right side
of the body and vice versa.
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The Central Nervous System
• The forebrain-telencephalon
• Frontal lobe
• The anterior portion of the cerebral cortex,
rostral to the parietal lobe and dorsal to the
temporal lobe. This includes everything in front
of the central sulcus.
• Parietal lobe
• The region of the cerebral cortex caudal to the
frontal lobe and dorsal to the temporal lobe.
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The Central Nervous System
• The forebrain-telencephalon
• Temporal lobe
• The region of the cerebral cortex rostral to the
occipital lobe and ventral to the parietal and frontal
lobes.
• Occipital lobe
• The region of the cerebral cortex caudal to the
parietal and temporal lobes. This is located posterior
to the central sulcus.
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The Central Nervous System
• The forebrain-telencephalon
• Sensory ____________ cortex
• Those regions of the cerebral cortex that receive
information from regions of the primary sensory
cortex. Perception takes place here and memories
are stored here.
• Motor association cortex (premotor cortex)
• The region of the frontal lobe rostral to the primary
cortex; also known as the premotor cortex. Controls
overall _________________________.
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The Central Nervous System
• The forebrain-telencephalon
• Prefrontal cortex
• The region of the frontal lobe rostral to the
motor association cortex. This region is involved
in formulating _____________________.
• Corpus callosum
• A large bundle of axons that ______________
corresponding regions of the association cortex
on each side of the brain.
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The Central Nervous System
• The forebrain-telencephalon
• ______________
• The phylogenetically newest cortex, including
the primary sensory cortex, primary motor cortex,
and association cortex.
• Limbic cortex
• Phylogenetically old cortex, located at the medial
edge of the cerebral hemispheres; part of the limbic
system.
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The Central Nervous System
• The forebrain-telencephalon
• Cingulate gyrus
• A strip of limbic cortex lying along the lateral
walls of the groove separating the cerebral
hemispheres, just above the corpus callosum.
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The Central Nervous System
• The forebrain-limbic system
• __________ system
• A group of brain regions including the anterior
thalamic nuclei, amygdala, hippocampus, limbic
cortex, and parts of the hypothalamus, as well
as their interconnecting fiber bundles.
• Hippocampus
• A forebrain structure of the temporal lobe,
constituting an important part of the limbic system;
includes the hippocampus proper, dentate gyrus,
and subiculum.
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• Limbic System Function:
• Most important for the
development of emotional
responses and __________.
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The Central Nervous System
• The forebrain -limbic system
• Amygdala
• A structure in the interior of the rostral temporal
lobe, containing a set of nuclei.
• Fornix
• A fiber bundle that connects the hippocampus with
other parts of the brain, including the mammillary
bodies of the hypothalamus.
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The Central Nervous System
• The forebrain -limbic system
• Mammillary bodies
• A protrusion of the bottom of the brain at the
posterior end of the hypothalamus, containing
some hypothalamic nuclei.
• Serve as relay stations in reflexes related to the
sense of smell.
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The Central Nervous System
• The forebrain-basal ganglia
• ___________________
• Part of the telencephalon, including the caudate
nucleus, the globus pallidus, and the putamen.
• ______________ disease is caused by degeneration
of the caudate nucleus and putamen.
• Parkinson’s disease includes weakness, tremors,
rigidity of the limbs, poor balance and difficulty initiating
movements.
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The Central Nervous System
• The forebrain-diencephalon
• Diencephalon
• Situated between the telencephalon and the
mesencephalon.
• A region of the forebrain surrounding the third
ventricle.
• The most important structures include the __________
and the _________________.
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The Central Nervous System
• The forebrain-diencephalon
• ____________ (Greek thalamos, “inner chamber”)
• The largest portion of the diencephalon, located
above the hypothalamus; contains nuclei that
project information to specific regions of the cerebral
cortex and receive information from it.
• Projection fiber
• An axon of a neuron in one region of the brain whose
terminals form synapses with neurons in another region.
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The Central Nervous System
• The forebrain-diencephalon
• Thalamus
• Lateral geniculate nucleus
• A nucleus of the thalamus that receives fibers
from the _________ and projects fibers to the primary
_________ cortex.
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The Central Nervous System
• The forebrain-diencephalon
• Thalamus
• ___________ geniculate nucleus
• A nucleus of the thalamus that receives fibers from
the auditory system and projects fibers to the auditory
cortex.
• Ventrolateral nucleus
• A nucleus of the thalamus that receives inputs from
the cerebellum and sends axons to the primary motor
cortex.
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The Central Nervous System
• The forebrain-diencephalon
• _________________
• A group of nuclei in the diencephalon situated
beneath the thalamus.
• Controls the autonomic nervous system.
• Controls the anterior and posterior pituitary glands.
• Organizes behavior such as fighting, feeding,
fleeing, and mating.
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The Central Nervous System
• The forebrain-diencephalon
• Hypothalamus
• Optic chiasm
• A connection between the optic nerves where half
of the fibers of the optic nerve cross to the
contralateral side
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The Central Nervous System
• The forebrain-diencephalon
• Hypothalamus
• Anterior _________ gland
• The “master gland”.
• The anterior part of the pituitary gland; an
endocrine gland whose secretions are controlled
by the hypothalamic hormones.
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The Central Nervous System
• The forebrain-diencephalon
• Hypothalamus
• Neurosecretory cell
• A neuron that secretes a hormone or hormonelike substance.
• Posterior pituitary gland
• The posterior part of the pituitary gland; an
endocrine gland that contains hormone-secreting
terminal buttons of axons whose cell bodies lie
within the hypothalamus.
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The Central Nervous System
• The midbrain-mesencephalon
• Midbrain
• The midbrain; a region of the brain that surrounds
the cerebral aqueduct; includes the tectum and
tegmentum.
• The mesencephalon; the central of the three major
divisions of the brain.
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The Central Nervous System
• The midbrain- mesencephalon
• Tectum (“roof”)
• The dorsal part of the midbrain; includes the
superior and inferior colliculi.
• ___________ colliculi
• Protrusions on top of the midbrain; part of the
visual system.
• In mammals they are primarily involved in visual
reflexes and reactions to moving stimuli
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The Central Nervous System
• The midbrain- mesencephalon
• Tectum
• ____________ colliculi
• Protrusions on top of the midbrain; part of the
auditory system.
• Brain stem
• The stem of the brain, from the medulla to the
diencephalon, excluding the cerebellum.
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The Central Nervous System
• The midbrain- mesencephalon
• Tegmentum (“covering”)
• The ventral part of the midbrain, includes the
periaqueductal gray matter, reticular formation,
red nucleus, and substantia nigra.
• ___________formation (reticulum means “little net”)
• A large network of neural tissue located in the central
part of the brain stem, from the medulla to the
diencephalon; plays a part in sleep, arousal attention,
movement, and various vital reflexes.
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The Central Nervous System
• The midbrain- mesencephalon
• Tegmentum
• Periaqueductal gray matter
• The region of the midbrain surrounding the cerebral
aqueduct; contains neural circuits involved in speciestypical behaviors such as fighting and mating; involved in
sensitivity to ________.
• Red nucleus
• A large nucleus of the midbrain that receives inputs from
the cerebellum and motor cortex and sends axons to
motor neurons in the spinal cord.
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The Central Nervous System
• The midbrain- mesencephalon
• Tegmentum
• Substantia nigra (“black substance”)
• A darkly stained region of the tegmentum that
contains neurons that communicate with the
caudate nucleus and putamen in the basal ganglia.
• Degeneration of the substantia nigra is involved
in _______________ disease.
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The Central Nervous System
• The hindbrain-metencephalon
• Hindbrain (4th ventricle)
• The most caudal part of the brain; includes
the metencephalon and myelencephalon.
• _____________ (“little brain”)
• A major part of the brain located dorsal to the pons,
containing the two cerebellar hemispheres, covered
with the cerebellar cortex; important component of
the motor system.
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The Central Nervous System
• The hindbrain-metencephalon
• Cerebellar cortex
• The cortex that covers the surface of the cerebellum.
• Deep cerebellar nuclei
• Nuclei located within the cerebellar hemispheres;
receive projections from the cerebellar cortex and
send projections out of the cerebellum to other parts
of the brain.
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• Cerebellum damage:
• Cerebellum receives visual,
auditory, vestibular, and
somatosensory input. It “smoothes”
and _____________ the outflow.
Damage results in poor
coordination, jerky, exaggerated
movements. Surgical or musical
abilities require the cerebellum.
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The Central Nervous System
• The hindbrain-metencephalon
• Cerebellar peduncle
• One of three bundles of axons that attach each
cerebellar hemisphere to the dorsal pons.
• Pons (“bridge”)
• The region of the metencephalon rostral to the
medulla, caudal to the midbrain, and ventral to the
cerebellum; appears to be important in
___________________________________.
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The Central Nervous System
• The hindbrain-meyencephalon
• Medulla oblongata
• The most caudal portion of the brain, located in
the myelencephalon, immediately rostral to the
spinal cord.
• Includes nuclei that control ________________ such
as the cardiovascular system, respiration, and
skeletal muscle tone.
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The Central Nervous System
• Spinal cord
• The cord of nervous tissue that extends caudally
from the medulla. (24 vertebrae)
• Spinal root
• A bundle of axons surrounded by connective
tissue that occur in pairs, which fuse and form
a spinal nerve.
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The Central Nervous System
• The spinal cord
• Cauda equina
• A bundle of spinal roots located caudal to the
end of the spinal cord.
• _________________
• The anesthesia and paralysis of the the lower
part of the body produced by injection of a local
anesthetic into the cerebrospinal fluid surrounding
the cauda equina.
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The Central Nervous System
• The spinal cord
• Dorsal root
• The spinal root that contains _____________ (afferent)
sensory fibers.
• Ventral root
• The spinal root that contains the ____________ (efferent)
motor fibers.
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• The Peripheral Nervous System
• The spinal nerves
• Spinal nerve
• A peripheral nerve attached to the spinal cord.
• Afferent axon
• An axon directed toward the central nervous system,
conveying _____________ information.
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The Peripheral Nervous System
• The spinal nerves
• Dorsal root ganglion
• A nodule on a dorsal root that contains cell bodies of
afferent spinal nerve neurons.
• Efferent axon
• An axon directed away from the central nervous system,
conveying _____________ commands to muscles and
glands.
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The Peripheral Nervous System
• Cranial nerves
• Cranial nerves
• ___________ pairs of peripheral nerves attached
directly to the brain that serve sensory and
motor functions of the head, neck, and shoulders.
13th cranial nerve: terminalis nerve – veromonasal organ.
• Vagus nerve (“wandering” – vagabond)
• The largest of the cranial nerves, conveying
efferent fibers of the parasympathetic division
of the autonomic nervous system to organs of
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The Peripheral Nervous System
• The autonomic nervous system
• Somatic nervous system
• The part of the peripheral nervous system
that controls the movement of skeletal muscles
or transmits somatosensory information to the
central nervous system.
• Autonomic nervous system
• The portion of the peripheral nervous system
that controls the body’s vegetative functions.
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The Peripheral Nervous System
• The autonomic nervous system-sympathetic
division
• _____________ division
• The portion of the autonomic nervous system that
controls functions that accompany arousal and
expenditure of energy.
• Sympathetic ganglia
• Nodules that contain synapses between preganglionic
and postganglionic neurons of the sympathetic nervous
system.
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The Peripheral Nervous System
• The autonomic nervous system-sympathetic
division
• Preganglionic neuron
• The efferent neuron of the autonomic nervous system
whose cell body is located in a cranial nerve nucleus
or in the intermediate horn of the spinal gray matter
and whose terminal buttons synapse upon
postganglionic neurons in the autonomic nervous system.
• Postganglionic neuron
• Neurons of the autonomic nervous system that form
synapses directly with their target organ.
99
Copyright © 2008 Pearson Allyn & Bacon Inc.
•
The Peripheral Nervous System
• The autonomic nervous system-sympathetic
division
• Adrenal medulla
• The inner portion of the adrenal gland, located
atop the kidney, controlled by sympathetic nerve
fibers; secretes epinephrine and norepinephrine.
100
Copyright © 2008 Pearson Allyn & Bacon Inc.
•
The Peripheral Nervous System
• The autonomic nervous system-parasympathetic
division
• Parasympathetic division
• The portion of the autonomic nervous system that
controls functions that occur during a relaxed state.
• Supports activities involved with increases in the body’s
supply of stored energy including salivation, gastric and
intestinal motility, secretion of digestive juices, and
increased blood flow to the gastrointestinal system.
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Copyright © 2008 Pearson Allyn & Bacon Inc.
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Copyright © 2008 Pearson Allyn & Bacon Inc.