Chapter 3 Structure of the Nervous System

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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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•
•
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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Copyright © 2008 Pearson Allyn & Bacon Inc.
•
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.
101
Copyright © 2008 Pearson Allyn & Bacon Inc.
102
Copyright © 2008 Pearson Allyn & Bacon Inc.
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