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O Desenvolvimento
do Sistema Nervoso
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Funo
receber informaes sobre as variaes externas e
internas e produzir respostas a essas variaes
atravs dos msculos e glndulas. a memria, que corresponde a capacidade de
armazenar informaes e depois resgat-las, o
aprendizado, o intelecto, o pensamento e a
personalidade.
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Organizao do Sistema NervosoSistema Nervoso
Sistema Nervoso Central Sistema Nervoso Perifrico
Encfalo Medula espinhal Diviso Aferente Diviso Eferente
NeurniosSensitivos
Somticos
NeurniosSensitivos
Viscerais
SistemaNervoso
Autnomo
SistemaNervoso
Somtico
Parte Simptica Parte Parassimptica
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Organizao do Sistema Nervoso
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Estrutura de um neurnio:
Corpo Celular
Ncleos
Centros
Gnglios
Componentes do Sistema Nervoso
Neurnios:
Unidade Morfofuncional do SN
No se multiplicam aps o nascimento, exceto os neurnios do bulbo
olfatrio, cerebelo e epitfalo olfatrio.
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Neurnio
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Pregas neurais
Sulco neuralTubo neural
O Tubo neural Se diferencia em
SNC, que consiste em encfalo e
Medula espinal
A Crista neural d origem s
clulas formadoras da maior parte
do SNP e SNA, constitudos pelos
gnglios cranianos, espinhais e
autnomos.
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Fechamento do
tubo neural em
ambos os sentidos
Neurporo ceflico 25 dia
Neurporo caudal
27 dia
Cristas neurais
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A, Dorsal view of an embryo of
about 23 days,
B, Lateral view of an embryo ofabout 24 days, showing the
forebrain prominence and
closing of the rostralneuropore.
C, Diagrammatic sagittal
section of this embryo, showing
the transitory communicationof the neural canal with theamniotic cavity (arrows).
D, Lateral view of an embryo of
about 27 days. Note that the
neuropores shown in B are
closed.
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Seco diagramtica sagital de embrio mostrando a comunicao
transitria do canal neural com a cavidade amnitica (setas)
A abertura ceflica o neurporo rostral, ou anterior, se fecha em tornodo 25 dia, o neurporo caudal, ou posterior, se fecha dois dias maistarde.
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As paredes do tubo neural se espessam, formando oencfalo e a medula espinhal.
O canal neural do tubo neural converte-se no sistemaventricular do encfalo e no canal central da medulaespinhal.
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Histognese dasClulas do SNC
After further
development the
multipolar neuroblast(lower left) becomes a
nerve cell or neuron.
Neuroepithelial cellsgive rise to all neuronsand macroglial cells.
Microglial cells are
derived frommesenchymal cellsthat invade the
developing nervous
system with the blood
vessels
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Tubo Neural
Extremidade ceflica
Hemisfrios cerebrais
encfalo
Anterior ou prosencfalo Mdio ou mesencfalo Posterior ou rombencfalo
Mesencfalo adulto
(tegumento, teto e
pednculosceflicos
Ponte, cerebelo e medula
(bulbo)
Tele e diencfalo
tlamo e hipotlamo
Meta e mielencfalo
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telencfalo diencfalo mesencfalo metencfalo mieloencfalo
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ENCFALO
VESCULAS ENCEFLICAS PRIMITIVAS
(1)O prosencfaloou encfalo anterior
(2)O mesencfaloou encfalo mdio
(3)O rombencfaloou encfalo posterior
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Diagrammatic sketches of the brain vesicles, indicating the adult derivatives of their walls and
cavities. *The rostral part of the third ventricle forms from the cavity of the telencephalon; most
of this ventricle is derived from the cavity of the diencephalon.
Vesculas pticas
Torna-se cada vez mais delgado
Organizao do sistema nervoso
A partir da 6semana
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Vista lateral das vesculas enceflicase parte alta da medula espinhal de
embrio de quatro semanas
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A, Schematic lateral view of an
embryo of about 28 days, showing
the three primary brain
vesicles: forebrain,midbrain, and hindbrain. Twoflexures demarcate the primary
divisions of the brain. B,
Transverse section of this embryo,
showing the neural tube that will
develop into the spinal cord in thisregion. The spinal ganglia derived
from the neural crest are also
shown. C, Schematic lateral view
of the central nervous system of a
6-week embryo, showing the
secondary brain vesicles and
pontine flexure. The flexure (bend)occurs as the brain grows rapidly.
O dobramento na 4 semana
importante para a modelagem do
sistema nervoso
Flexura cervical
Flexura ceflica
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FLEXURAS ENCEFLICAS
Flexura Cervical:Entre o rombencfalo e a medula espinal
Flexura Ceflica:No mesencfalo
Flexura Pontina: Entre o metencfalo e o mielencflo
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Esquema mostrando a formao das flexurasceflicas, cervical e pontina
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Rombencfalo
Podem ser claramente distinguidas as placas alar ebasal, separadas pelo sulco limitante.
Contm ncleos
motores
Mielencfalo
Colunas de ncleos (agregadosde corpos celulares neuronais noencfalo) viscerais aferentes(indo p/ o encfalo) eeferentes (saindo do encfalo).
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XII- (Hipoglosso)- MotorXI- Acessrio (Motor); X-vago(misto)IX-Glossofarngeo(misto).
A placa do teto do mielencfalo, est constituda por uma nica camada declulas ependimrias, recobertas externamente pela pia-mter(mesnquimavascular). Essas estruturas constituem o plexo coride, produtor do lquido
cefalorraquidiano.
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Colculos superiores
Colculos inferiores
Centros de Reflexosauditivos
Centro deReflexos visuaisOs Colculos formam-se por
intensa proliferao de clulasdo manto que migram para zona
marginal
Os ncleos do III nervo craniano oculomotor- a partir das placasbasais, localizam-se ao nvel dos
colculos superiores
Os ncleos do IV nervo craniano-troclear a partir das placasbasais, localizam-se ao nvel doscolculos inferiores
Mesencfalo
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Vista externa do encfalono fim da quinta semana
Hemisfrios
cerebrais crescem
e cobrem
diencfalo,
mesencfalo e
rombencfalo
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A, Sketch of the developing brain at the end of the
fifth week. C Sagittal sections of the hindbrain at
6 and 17 weeks, respectively, showing successive
stages in the development of the pons andcerebellum.
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Formao da medula espinhal
O tero caudal da placa e do tubo neural representa a futuramedula espinhal.
Diagrama ilustrando o desenvolvimento da medula espinhal
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Formao das Meninges da Medula Espinhal
A dura-mter do mesnquima mesodermaque envolve o tubo neural.
As Leptomeninges pia-mter e a aracnideoriginam-se das clulas das cristas neurais.
Durante a quinta semana, comea a formar-se um
fluido cerebro
espinhal (FCS, lquor), que podeconstituir um meio nutritivo para as clulas epiteliais
dos tecidos neurais.
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Sistema
Nervoso
Perifrico
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Pregas neurais
Sulco neuralTubo neural
O Tubo neural Se diferencia em
SNC, que consiste em encfalo e
Medula espinal
A Crista neural d origem s
clulas formadoras da maior partedo SNP e SNA, constitudos pelos
gnglios cranianos, espinhais e
autnomos.
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Diagrams showing some
derivatives of the neural
crest.
Neural crest cells also
differentiate into the cellsin the afferent ganglia of
cranial nerves and many
other structures The
formation of a spinal
nerve is also illustrated.
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Os nervos cranianos podem ser subdivididos com base em suaf i b i l i
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funo ou em sua origem embriolgica.
motor
Sensitivo
O vago misto,
predominantementemotor
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Anomalias
Congnitas do
Sistema Nervoso
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3 a cada mil nascimentos
Geralmente devido a fatores multifatoriais
Tipos
Estruturais
Distrbios na organizao das clulas
Erros de metabolismo
Diagnosticados por alto nvel de alfa-fetoprotena no lquido
amnitico ou por ultrasson
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Schematic illustrations
explaining the
embryological basis ofNTDs. Meroanencephaly -
partial absence of the
brain - results from
defective closure of the
rostral neuropore, and
meningomyelocele results
from defective closure of
the caudal neuropore.
Defeitos de fechamento
do tubo neural
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female child with a hairy patch in
the lumbosacral region, indicating
the site of a spina bifida occulta
Photographs of infants with spina bifida
cystica. A, Spina bifida with
meningomyelocele in the lumbar region.
B, Spina bifida with myeloschisis in the
lumbar region. Note the nerve
involvement has affected the lower limbs.
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Photograph of the back of a newborn with a large lumbar meningomyelocele. The
neural tube defect (NTD) is covered with a thin membrane. (Courtesy of Dr. AE
Chudley, Section of Genetics and Metabolism, Department of Pediatrics and Child
Health, Children's Hospital and University of Manitoba, Winnipeg, Manitoba,
Canada.).
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Photograph of a 19-week female fetus showing an open
spinal defect in the lumbosacral region (spina bifida with
meningomyelocele). (Courtesy of Dr. Joseph R. Siebert,
Children's Hospital and Regional Medical Center, Seattle,
Washington.).
A, Photograph of a human embryo of about 30 days. The
white arrow indicates the site of the NTD resulting from
failure of closure of the caudal neuropore. Normally this
neuropore is closed by day 28. B, Photomicrograph of a
transverse section through the NTD. The black arrow
indicates an abnormal fold of neural tissue extending over
the left side of the embryo. It appears that this overgrown
neural fold has prevented closure of the neural tube.
Meningoencefalocele
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Schematic drawings illustrating cranium bifidum (bony defect in cranium) and various types of
herniation of the brain and/or meninges. A, Sketch of the head of a newborn infant with a large
protrusion from the occipital region of the cranium. The upper red circle indicates a cranial
defect at the posterior fontanelle. The lower red circle indicates a cranial defect near the
foramen magnum. B, Meningocele consisting of a protrusion of the cranial meninges that is
filled with cerebrospinal fluid (CSF). C, Meningoencephalocele consisting of a protrusion of part
of the cerebellum that is covered by meninges and skin. D, Meningohydroencephalocele
consisting of a protrusion of part of the occipital lobe that contains part of the posterior horn of alateral ventricle.
Meningoencefalocele
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Photograph of an infant with a large meningoencephalocele in the occipital area.
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Sonogram of a normal fetus at 12 weeks' gestation (left) and a fetus at 14 weeks'
gestation showing acrania and meroanencephaly (right).
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Photograph of an infant with
microcephaly, showing the typical
normal-sized face and small calvaria.
Microcefalia condio
relativamente incomum
Subdesenvolvimento do
encfalo e do crnio
Pode resultar de fechamentoprematuro das suturas
cranianas
Etiologia geralmente incerta
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, Photograph of an infant with hydrocephalus and bilateral cleft palate. B and C, Photographs showing the
brain of a 10-year-old child who had developed hydrocephalus in utero as a result of aqueduct stenosis. The
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