THE NERVOUS SYSTEM
Chapter 7
• Monitors changes-__________________________-inside and outside the body
• Processes and interprets input________________________________
• Effects a response by activating muscles or
glands(effector)via_____________________________
________
Stimuli and gathered info is
sensory input
integration
Motor output
Organization of the Nervous
System
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Divided by structure and activities
Structural classification
_____________________________________-consists of brain and
spinal cord and is integrating command center
__________________________________-part of system outside CNSnerves extending beyond the brain and SC
_______________________________-carry messages to and from SC
and
______________________________-carry impulses to and from brain
CNS
Peripheral
nervous
system
Spinal
nerves
Cranial nerves
Functional classification
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Divides peripheral nervous sytem into 2 divisions
__________________or afferent division consists
of nerves conveying info to CNS via sensory
receptors in the body
__________________________-bring in impulses
from skin,skeletal muscles and joints
________________________________bring in
messages from inside and outside the body
sensory
Somatic
sensory
fibers
Visceral or
sensory
fibers or
afferents
effect
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Somatic nervous system
Voluntary nervous
sysyem
Motor or efferent division carry impulses from CNS to
effector organs-muscles and glands-They _________a motor
response
a)______________________allows us to consciously,or
voluntarily control skeletal musces-so this sytem is also
called ______________________________/some skeletal
responses are initially involuntary
b) __________________ regulates autonomic or involuntarylike smooth muscle ,cardiac muscle and glands…..commonly
called ______________________,which has 2 parts
:1)sympathetic-opposes parasympathetic-associated w/ flight
or fight 2)parasympathetic division-opposes sympathetic
and craniosacral division
Involuntary NS
Autonomic nervous
system
Nervous Tissue:Structure and
Function
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Either supporting cells or neurons
Supporting Cells-limped together as neuroglia
and includes cells that generally support,insulate
and protect delicate neurons---glial cells have
special functions:
• ______________________________-abundant star
shaped cells-swollen ends that cling to neurons,bracing
them and anchoring to nutrient
supply:________________________/They form a living
barrier between capillaries and neurons and help make
exchange between the 2-help protect neurons from
harmful substances in the blood and also help control
brain chemical environment by “mopping”up leaked K
ions and recapturing released neurotransmitters
• _____________________________-spider like
phagocytes to dispose of debris-like dead brain cells and
bacteria
astrocytes
capillaries
microglia
ependymal
oligiodendrocytes
• _____________________________-glial cells that line
the central cavities of the brain and SC …..beating of
cilia to distribute cerebrospinal fluid for those cavities
and provide a cushion
• _________________________________-glia that wrap
flat extensions tightly around nerve fibers-producing fatty
myelin sheath(an insulation)
• 2 major varieties in PNS:______________________form
myelin sheath and
______________________________-positive
cushioning cells
Schwann cells
Satellite cells
Neurons-- anatomy-all have cell body,which contains nucleus and
is metabolic center and one or slender extending processes
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Neurons-- anatomy-all have cell body,which contains nucleus
and is metabolic center and one or slender extending
processes
Cell Body-metabolic center
Transparent ________________ w/ a conspicuous nucleolus
Cytoplasm has usual organelles except centrioles
Rough ER is called______________________________and
_____________________________(intermediate filaments
used in maintaining cell shape)
nucleus
Nissal substance
neurofibrils
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Processes-or fibers- vary greatly in length from
microscopic - ~3-4 ft.Our longest reach from lumbar to
large toe
________________________-convey incoming
messages(electrical signals) towards cell body-may be
many of these for one nerve cell
_____________________- carry messages AWAY
from cell body-only 1 axon,but branch much 2 end
w/hundreds of axon
_____________________________.-they contain
100’s of tiny vesicles,or membranous sacs
w/___________________________chemicalsreleased into extracellular space
axons
dendrites
Axon
terminals
neurotransmitters
• _____________________________tiny gap that
separates axon terminal from next neuron(synapse)
• _____________________________-whitish ,fatty
material w/waxy appearance.It functions by
insulating or protecting fibers and Increases
transmission rate
Myelin sheath
Synaptic cleft
• Axons outside CNS are myelinated by
____________________________,which
is gradually squeezed tightly enclosing
axon
• External to Schwann cell is neurilemma-
Schwann cells
• Gaps between Schwann cells are called
__________________________
• Myelinated fibers also in CNS as
___________________________-around small segment of 1
nerve fiber-coiling around as many as 60 fibers at one
time…Since they lack neurilemma that contributes to non –
regeneration property
Nodes of
Ranvier
oligodendrites
• __________________________________
is a neurological disorder causing visual or
speech problems as wel as increasingle
degenerating muscle …This is all due to
an autoimmune response that destroys a
protein in the myelin and cause nerves to
short ciruit----Interferon is used
Multiple
sclerosis
Terminologynuclei
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ganglia
cell bodies in CNS are usually called ______________-carrying out metabolic functions/not regenerated
__________________small collections of cell bodies outside
CNS-in PNS
________________________ are bundles of nerve fibers
running through CNS
_____________________________________ are bundles of
nerve fibers running through PNS
_________________________-collections of myelinated fibers
in CNS
________________________CNS unmyelinated fibers
nerves
tracts
Gray matter
White matter
Classification
Sensory or
afferent
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Functionally groups neurons according to
direction of nerve transmission relative to CNS…if
carrying impulse from receptor to CNS____________________________neurons-found in
a ganglion outside CNS;dendrite endings of
sensory neurons are usually associated with
specialized recptors activated by specific nearby
changes-cutaneous sense organs
and_____________________________in muscle
and tendons
proprioreceptors
• _________________(efferent)neurons carry
impulses from CNS to visceraan/or muscles or
glands-cell bodies in CNS
• ________________________or association neurons
connect motor and sensory neurons in neural
pathways-cell bodies always in CNS
• Structurally based on # of processes extending from
cell body---if
several:____________________________-inc. all
motor and association
neurons/__________________neurons have 2
processes-rare in
adults/_____________________neurons have single
process –sensory neurons in PNS
motor
bipolar
interneurons
multipolarneuron
Unipolar neurons
6-Physiology
• NERVE INPULSES:Neurons have 2 major properties___________________________________________
• __________________________refers to inactive or
resting plasma membrane(fewer + ions on inner
face(K+ions)-outside are Na+ ions …if the inside is
more - ,it is inactive
Irritability and
conductivity
polarized
depolarization
repolarization
Action
potential
• Action Potential and generation:…many different stimuli
excite neurons—eg.light,sound,pressure-most excited by
neurotransmitters released by other neurons….changes
permeability of membrane changes briefly-gates of Na
channels open---changing polarity_________________________-inside now more +-graded potential
• If this strong enough it initiates
an_________________________(nerve impulse)-all-or
none response
• An outflow now of K+ ions will restore resting state__________________________________
• UNTIL REPOLARIZATION HAPPENS<A
NEURON CANNOT CARRY ANOTHER
IMPULSE !
• NA-K pump uses ATP
• The above describes unmyelinated impulses –
Myeinated sheaths conducts impulses faster__________________________________leaps from node to node
• Conductivity can be impaired by sedatives and
anesthetics by altering permeability
Salatory
conduction
• Synapse Transmission-impulse does not
traverse- synapse neurotransmitter do and
they cause Na+ entry ,depolarization,etc.brief transmission-electrochemical
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Reflexes-rapid and predictable and
involuntary response to stimuli
Somatic reflexes-stimulate skeletal
muscles
_____________________regulate
smooth muscles,heart and glands
Autonomic
reflexes
• _____________________________is a neural
pathway and has at least 5
elements:____________________________________
_____________________________________________
___________________
Relex arcs
Sensory receptor,effector
organ,sensory or motor
neurons and synapse-CNS
integration center
gyri
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sulci
III. CNS
Functional Anatomy of the Brain
– Brain is ~ 3 lbs.
– 4 regions-cerebral,diencephalons,brain
stem,cerebellum
• Cerebral hemispheres
Paired
Largest and most superior
____________-elevated regions of tissue separated
by shallow _______
______________________are less numerous
grooves and separate larger regions of brain
fissures
Longitudinal
fissure
• ______________-separates 2
hemispheres by deep fissure
• Other fissures or sulci divide into
lobes,named for corresponding cranial
bone
• 3 basic regions to ea
hemisphere:_______________________
Superficial cortex of gray matter,internal white
matter,and basal ganglia(Gray)
Cerebral Cortex:-includes speech,memory,logical and
emotional response, consciousness , interpretation of
sensation,and voluntary movement
– ________________________-posterior to central
sulcus-primary somatic sensory area-interprets
impulses traveling from body sensory
receptors(except for special senses)/allows you to
perceive pain,coldness or light touch….as shown in 714,p.245…body is represented in an upside down
manner in sensory area-such a spatial map is a
___________________-crossed pathways-left
primary somatic sensory area receives impulse from
right and vice verse
Primary somatic
sensory area in
parietal lobe
Sensory
homunculus
– __________________________visual area in
posterior
– ___________________________has auditory
area and has olafactory area
– _________________________is primary
motor area/the axons of these motor neurons
make ________-major voluntary motor tract
and it descends to cord-pathways again
crossed
– _________is map on motor cortex
Occipital lobe
Frontal
lobe
Temporal lobe
Corticospinal or
pyramidal tract
Motor
homunculus
– ______________________at base of precentral
gyrus-involved in speech-usually only in left
hemisphere-damage here can cause inability to say
words properly
– In anterior frontal lobes is believed to be intellectual
reasoning and socially acceptable behavior region
– The main _____________________is located at
junction of temporal,parietal,and occipital lobesusually only in 1 hemisphere also
– __________________is involved w/word meanings
– Cell bodies of neurons involved in cerebral
hemisphere are in outermost gray matter
Broca’s
area
Speech area
Frontal lobes
Cerebral White Matter-deeper,remaining cerebrumcomposed of fiber tracts carrying impulses to and from
or within cortex
• __________________________________-large fiber
tract that connects cerebral hemispheres(an
example of a commisure)-allows hemispheres to
communicate with each other….Association fiber
tracts connects areas w/in hemisphere and
projection fiber tract connects cerebrum
Corpus callosum
• _______________________________islands of gray matter buried in white
matter of cerebral hemispheres-help
regulate voluntary motor activities by
modifying instructions-esp. starting or
stopping
• basal ganglia
Basal nuclei
• ______________________________- genetic disease,
middle-age and leads to massive degeneration of
basal nuclei and then cerebral cortex-includes jerky
movements and an eventual vegetative state w/in 15
years fatal-overdrive in motor stimulation
• ______________-has basal nuclei problems-strikes
in 50’s-60’s and comes from a degeneration of
dopamine releasing neurons-dopamine deprived
basal nuclei become overactive-tremors,head
nodding etc.
Huntington’s
disease or
Chorea
Parkinson’s
disease
*Diencephalon-interbrain-atop brain stem and enclosed
by cerebral hemispheres
• ____________________________-encloses shallow
3rd ventricle of brain and is relay station for sensory
impulses passing upward to sensory cortex-interpret
sensation
• ____________________________________-is under
the thalamus makes up floor of diencephalons-helps
regulate body temp.,water balance and,metabolismalso centers for many drives and emotions-part of
___________________________-“emotional visceral
brain”-thirst,appetite and sex drive
Thalamus
hypothalamus
Limbic System
• Contains pituitary gland and mammillary
bodies that is involved in olafaction
• ___________________-roof of 3rd
ventricle/contains
____________________-an endocrine
organ,choroid plexus-form cerebrospinal
fluid
epithalamus
Pineal body
____________________________________-about the size of a
thumb in diameter and about 3’’ long…includes midbrain,pons
and medulla oblongata/provides a pathway for ascending and
descending tracts and has small gray matter areas
» 1)____________________________small/____________________________________
travels through midbrain and anteriorly midbrain
has cerebral peduncles that convey ascending
and descending impulses/dorsally are 4 rounded
corpora quadrigemina-reflex centers for vision
and hearing
midbrain
Brain stem
Cerebral
aqueduct
» 2)___________________----rounded just
below midbrain and has bridge of fiber
tracts and involves in control of
breathing
» 3)___________________________-most
inferior part and merges into SC…fiber
tract area and helps regulate visceral
activity
pons
Medulla oblongata
***Cerebellum-dorsally under occipital lobe and has 2
hemispheres-has outer cortex of gray matter and inner
cortex of white matter
» Provides timing factor for skeletal and
controls muscle activity
• ________________________-cerebellum damage
causing clumsiness and disorganization
ataxia
Protection of CNS
• A.__________-3 connective tissue membranes
protecting CNS
– 1)______________________-outermost layer and
leathery(“tough or hard mother”),double layered
where surrounds brain
Dura mater
meninges
• _____________________-attached to inner
surface of skull
• ___________________-Outermost covering of
brain and continues as dura mater of spinal cord
• Dural layers fused except in 3 areas where they
separate to enclose dural venous sinuses that
collect _________________________.
Periosteal layer
Venous blood
Meningeal layer
Inner dural membrane extends inward to form a
fold that attaches brain to cranial cavity
______________________________-middle
meningeal layer,weblike;spans
subarachnoid space to attach TO innermost
membrane.
Arachnoid
mater
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3)_____________________________-innermost
membrane(“gentle mother”)-clings tightly to
surface of brain and spinal cord,following every
fold
Subarachnoid space is filled w/ cerebrospinal
fluid and
______________________________protrude
through dura mater
Cerebrospinal fluid is absorbed into venous
blood in dural sinuses through arachnoid villi
Projections of arachnoid
membrane called
arachnoid villi
Pia mater
encephalitis
• ______________________________inflammation of meninges,serious threat to
brain(bacterial or viral) because may spread to the
nervous tissue of the CNS/spinal diagnostic taps
derived from subarachnoid space
• ___________________________-brain
inflammation
meningitis
Cerebrospinal Fluid(CSF)-somewhat watery and similar
to blood plasma,but contains less protein and more
vitamin C and a different ion composition
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CSF continually formed from blood by choroids
plexus(clusters of capillaries hanging from roof of each
of brain’s ventricles)
Forms a watery cushion to protect fragile nervous
tissue
Continually moves in brain,circulating from 2
_________________________into 3rd ventricle and
then through cerebral aquaduct of midbrain into 4th
ventricle….some of this continues down SC,but most
circulates into subarachnoid space
Lateral
ventricles
• CSF returns to blood in dural venous sinuses
through _____________________________
• Normal means CSF forms and drains at a
constant rate maintaining about ½ cup fluid.Any
significant changes-like blood cells or general
composition may mean
____________________
• Test w/ lumbar puncture
• ________________________________--if
drainage of CSF is obstructed-maybe by tumor
or born that way
Arachnoid villi
hydrocephalis
Sign of
miningitisor
certain brain
pathologies
such as tumor
or MS
Blood-Brain Barrier
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Brain is very sensitive to pressure and chemical changes
Thus,the least permeable capillaries in body—almost
seamlessly bound by tight junctions all around-passing only
water ,glucose and amino acids pass easily through—
preventing _________________________
Barrier useless against
____________________________(thus explains entrance of
alcohol,nicotine and anesthetics
Preventing urea,
toxins,proteins and
many drugs from
entering
Fats,respiratory gases
and other fat-soluble
molecules
Brain Dysfunctions
• _______________________________-progressive
degenerative disease of brain resulting,eventually, in
dementia;associated w/shortage of Ach and
structural changes in brain;gyri shrink and brain
atrophies
• _______________________-minor and not permanent
brain damage
• __________________________-marked tissue
destruction-severe forms always result in comas
Alzheimer’s
disorder
concussion
contusion
• ____________________________-after a blow to the head-bleed
from ruptured vessels
• ________________________-swelling of brain from
inflammatory response to injury
• ______________________________-3rd leading cause of death
in US-when blood circulation is blocked and vital tissue dies
• ____________________one sided paralysis
• _________________damage to left cerebrum and affects
speech
• __________________-temporary restriction of blood flow
Intracranial
hemorrhage
hemiplegia
Cerebral edema
Cerebrovascular
accidents-CVAie.stroke
aphasias
Transient ischemic attack
-TIA
SPINAL CORD-cylindrical and appx.17” long,glistening
white;2 way conduction pathway to and from brain and
reflex center
• Extends from foramen magnum to
_________________________________,ending below the
ribs(thus L3 good for spinal tap)
• Protected by CSF and meningeal coverings
• 31 prs spinal nerves-arise from cord and exit from vertebral
column to serve nearby area of body
• ____________________collection of spinal nerves at end of
vertebral canal
1st or 2nd lumbar
vertebra
Cauda equina
A)Gray matter of SC and spinal roots
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Looks like butterfly in crosssection
Contains dorsal horns(has interneurons) ,ventral
horns(contain cell bodies of motor somatic{voluntary}
nervous sytem and surrounds central canal of SC
,containing CSF)
Cell bodies of sensory neurons enter cord by dorsal root
and are called ___________________________________-If
severed ,sensation at that point is lost
Ventral horn sends its axons out
______________________
Dorsal and ventral roots fuse to form
________________________________
____________________________-damage to ventral
root/affecting muscles served;muscles will atrophy
Spinal nerves
Dorsal root
ganglion
Ventral root of cord
Flaccid paralysis
B-White matter of SC
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Myelinated fiber tracts-serving higher centers,some travel
brain to SC and some innervate one or the other side of the
SC
Dorsal,lateral and ventral columns-3 regions of white matter
Tracts conducting Sensory impulse to brain by
_________________or afferent tracts
Motor(efferent tracts) carry from
__________________________________
__________________________________-if SC is cut
crosswise or crushed-afferent stay intact and involuntary
movement of those muscles results and sensation loss
below cut-compare quadriplegic to paraplegic
sensory
Brain to skeletal
muscles