Copyright © 2008 Pearson Allyn & Bacon Inc. 1 Chapter 3 Structure of the Nervous System This multimedia product and its contents are protected under copyright.

Copyright © 2008 Pearson Allyn & Bacon Inc.1

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



• 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.




• ___________• 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.



• ____________• “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.



• __________• “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.



• ___________• 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.



• _______________• 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.



• _____________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.




• 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.



• 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.



• 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.



Dura mater

Arachnoid membrane

Subarachnoid space[Blood vessels and cerebrospinal fluid (CSF)]

Pia mater

Central nervous system tissue


• 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.



• 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_____________________.




• 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.




• 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.




• 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.


• CSF Reabsorbtion:

• CSF production and reabsorption must occur at the __________.

• Reabsorbtion occurs in the subarachnoid space around the CNS (reabsorbed into the blood).

• Hydrocephalic??


• Hydrocephalic skull




• 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.


• Subdivisions of the brain:

• Forebrain• ___encephalon (end brain)• ___encephalon (interbrain)

• Midbrain• ___encephalon

• Hindbrain• ___encephalon (afterbrain)• __elencephalon (marrowbrain)





• 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.




• 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.

• Cerebral cortex grows from the inside out:

• Neurons _____ along the radial fibers like _________, pushing past the neurons that were born earlier.






• 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.)




• ___________________ 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.

• 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!


Neurogensis:

Old Belief: adult brains do not display neurogensis.

New Data: stem cells (founder cells) are found in olfactory bulb & ____________


• Neurogensis:

• Exposure to new odors increases survival rate of new olfactory bulb neurons.

• Learning tasks enhance neurogenesis in the hippocampus (declarative memory tasks)


• Suppression of neurogenesis:

• Depression and stress depress neurogenesis in the hippocampus.

• Drugs that reduce stress and depression reinstate neurogenesis in the hippocampus.


• 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.





• 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.




• 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.




• 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.

•Axons & cell bodies

•________matter: myelinated axons.

•______matter: cell bodies.






• 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 primaryvisual cortex is located along its upper and lowerbanks.




• 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.




• 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.




• 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.





• Frontal lobe• The anterior portion of the cerebral cortex,

rostral to the parietal lobe and dorsal to thetemporal lobe. This includes everything in frontof the central sulcus.

• Parietal lobe• The region of the cerebral cortex caudal to the

frontal lobe and dorsal to the temporal lobe.




• 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.






• Sensory ____________ cortex• Those regions of the cerebral cortex that receive

information from regions of the primary sensorycortex. Perception takes place here and memoriesare stored here.

• Motor association cortex (premotor cortex)• The region of the frontal lobe rostral to the primary

cortex; also known as the premotor cortex. Controlsoverall _________________________.




• 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.




• ______________• 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.




• Cingulate gyrus• A strip of limbic cortex lying along the lateral

walls of the groove separating the cerebral

hemispheres, just above the corpus callosum.



• The forebrain-limbic system

• __________ system• A group of brain regions including the anterior

thalamic nuclei, amygdala, hippocampus, limbiccortex, and parts of the hypothalamus, as wellas 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.

•Limbic System Function:

•Most important for the development of emotional responses and __________.




• 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 mammillarybodies of the hypothalamus.



• The forebrain -limbic system

• Mammillary bodies• A protrusion of the bottom of the brain at the

posterior end of the hypothalamus, containingsome hypothalamic nuclei.

• Serve as relay stations in reflexes related to thesense of smell.




• 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.




• The forebrain-diencephalon

• Diencephalon• Situated between the telencephalon and the

mesencephalon.

• A region of the forebrain surrounding the thirdventricle.

• The most important structures include the __________and the _________________.




• ____________ (Greek thalamos, “inner chamber”)• The largest portion of the diencephalon, located

above the hypothalamus; contains nuclei thatproject information to specific regions of the cerebralcortex 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.




• Thalamus

• Lateral geniculate nucleus• A nucleus of the thalamus that receives fibers

from the _________ and projects fibers to the primary

_________ cortex.




• 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 motorcortex.




• _________________• 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.





• Hypothalamus

• Optic chiasm• A connection between the optic nerves where half

of the fibers of the optic nerve cross to the

contralateral side




• Hypothalamus

• Anterior _________ gland• The “master gland”.

• The anterior part of the pituitary gland; an

endocrine gland whose secretions are controlled

by the hypothalamic hormones.




• Hypothalamus

• Neurosecretory cell• A neuron that secretes a hormone or hormone-

like substance.

• Posterior pituitary gland• The posterior part of the pituitary gland; an

endocrine gland that contains hormone-secretingterminal buttons of axons whose cell bodies liewithin the hypothalamus.




• The midbrain-mesencephalon

• Midbrain• The midbrain; a region of the brain that surrounds

the cerebral aqueduct; includes the tectum andtegmentum.

• The mesencephalon; the central of the three majordivisions of the brain.



• 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




• 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.




• 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.




• Tegmentum

• Periaqueductal gray matter• The region of the midbrain surrounding the cerebral

aqueduct; contains neural circuits involved in species-typical 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.




• Tegmentum

• Substantia nigra (“black substance”)• A darkly stained region of the tegmentum that

contains neurons that communicate with thecaudate nucleus and putamen in the basal ganglia.

• Degeneration of the substantia nigra is involvedin _______________ disease.




• 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, coveredwith the cerebellar cortex; important component ofthe motor system.




• 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 andsend projections out of the cerebellum to other partsof the brain.

• 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.





• 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 thecerebellum; appears to be important in ___________________________________.



• The hindbrain-meyencephalon

• Medulla oblongata• The most caudal portion of the brain, located in

the myelencephalon, immediately rostral to thespinal cord.

• Includes nuclei that control ________________ suchas the cardiovascular system, respiration, andskeletal muscle tone.



• 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 forma spinal nerve.




• 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 localanesthetic into the cerebrospinal fluid surroundingthe cauda equina.



• The spinal cord

• Dorsal root• The spinal root that contains _____________ (afferent)

sensory fibers.

• Ventral root• The spinal root that contains the ____________ (efferent)

motor fibers.



• 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.



• 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.





• Cranial nerves

• Cranial nerves• ___________ pairs of peripheral nerves attached

directly to the brain that serve sensory andmotor 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 divisionof the autonomic nervous system to organs ofthe thoracic and abdominal cavities.




• The autonomic nervous system

• Somatic nervous system• The part of the peripheral nervous system

that controls the movement of skeletal musclesor transmits somatosensory information to thecentral nervous system.

• Autonomic nervous system• The portion of the peripheral nervous system

that controls the body’s vegetative functions.



• 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.




• Preganglionic neuron• The efferent neuron of the autonomic nervous system

whose cell body is located in a cranial nerve nucleusor in the intermediate horn of the spinal gray matterand whose terminal buttons synapse uponpostganglionic neurons in the autonomic nervous system.

• Postganglionic neuron• Neurons of the autonomic nervous system that form

synapses directly with their target organ.




• Adrenal medulla• The inner portion of the adrenal gland, located

atop the kidney, controlled by sympathetic nervefibers; secretes epinephrine and norepinephrine.



• 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.


Copyright © 2008 Pearson Allyn & Bacon Inc. 1 Chapter 3 Structure of the Nervous System This multimedia product and its contents are protected under copyright.

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