Development Of The Nervous System Flashcards
1
Q
When does gastrulation occur
A
Third week of embryogenesis
2
Q
Sequence of events in gastrulation
A
- ectoderm becomes epiblast where they remain
- some epiblast invaginate and form primitive streak and node
- some epiblast detach and form mesoderm
- some epiblast move further deep and begin to replace cell of hypoblast to become endoderm
3
Q
What are the 3 different structures that are involved in the development of the nervous system
A
- Notochord
- Neural tube
- Neural crest
4
Q
What is one of the first systems to develop
A
Nervous
5
Q
What forms first for the nervous system
A
Notochord
6
Q
This initiates the formation of the neural tube
A
Notochord
7
Q
Later becomes the nucleus pulposus
A
Notochord
8
Q
Gives rise to the CNS
A
Neural tube
9
Q
Gives rise to the PNS
A
Neural crest
10
Q
Notochord formation
A
Cells move rostrally, forming notochord from primitive node to prechordal plate
- notochord firmed during gastrulation and then induces the formation of neural tube (neurlation)
- later becomes nucleus pulposus of vertebrae
11
Q
What induces the formation of the neural plate (neurlation)
A
Notochord
12
Q
What does the CNS develop from
A
Ectoderm
13
Q
What gives rise to the brain, spinal cord, and PNS?
A
Specialized part of ectoderm called the neuroectoderm
14
Q
What forms the primitive streak
A
Ectodermal cells form this migrating rostrally forming the neural plate
15
Q
The first step of the neural system development is the formation of
A
The neural plate ***
16
Q
This induces the overlying region of the ectoderm to form the neural plate
A
Notochord
17
Q
Where does the neural plate invaginate
A
Along the longitudinal axis and formed neural groove
18
Q
Neural plate becomes the
A
Neural groove
19
Q
Around day 21, the neural groove begins to close to become
A
The neural tube
20
Q
When is the neural tube closed by
A
Day 28
21
Q
Where does neural tube development initiate
A
At the cervical region and proceeds rostrally and caudally
22
Q
The ____________ segments of the spinal cord and their corresponding dorsal and ventral roots are formed by secondary neurulation
A
Sacral and coccygeal
23
Q
When does secondary neurulation occur
A
Day 20 and is complete by about day 42
24
Q
This appears caudal to the neural tube and then enlarges and cavitates. It then joins the neural tube and its cavity becomes continuous with the neural canal
A
Caudal eminence
25
Disorder in which the conus medullaris and fill up terminale are abnormally fixed to the defective vertebral column
Tethered cord syndrome
26
PNS develops from
Neural crest cells
27
Where do neural crest cells arise from
Lateral edge of the neural plate
28
Where do neural crest cells move when they detach from the lateral edge of hte neural plate
Move to locations lateral to the neural tube
29
What are some neural crest derivatives
Neural
- posterior root ganglia
- paravertebral (symp chain) ganglia
- prevertebral (preaortic) ganglia
- enteric ganglia
- parasympathetic ganglia of CN VII, IX, and X
- sensory ganglia of CN V, VII, VIII, IX, and X
30
When does anterior neuropore close
4th week
31
When are the three primary brain vesicles formed
4th week
32
What do the three primary brain vesicles divide the brain into
- prosencephalon (forebrain)
- mesencephalon (midbrain)
- rhombencephalon (hindbrain)
33
What are the two flexures that develop in week 4
- cervical flexure
| - mesencephalic flexure
34
Embryonic Flexure between the hindbrain and the spinal cord
Cervical flexure
35
A second bend in the neural tube at the level of the mesencephalon
Mesencephalic flexure
36
When do the 3 primary brain vesicles divide into 5 secondary brain vesicles
Week 5
37
What additional flexures appear during 5th week
- pontine flexure divides the hindbrain into the myelencephalon caudally an the metencephalon rostrally
- telecephalic flexure forms between the diencephalon and the telencephalon
38
Does the mesencephalon partition further after the fifth week?
No
39
What does the telencephalon do at the 5th week
Expands and forms the cerebral hemispheres
40
Optic cup at 5th week
Optic cup and nerves bulge from the diencephalon to form eye
41
What does the forebrain divide into
Telencephalon and diencephalon
42
What does the midbrain divide into
Mesencephalon only
43
What does the hindbrain divide into
- metencephalon
| - myelencephalon
44
Derivatives of the telencephalon
- cerebral hemispheres
- olfactory cortex
- hippocampus
- basal ganglia
- lateral and 3rd ventricle
45
Derivatives of the diencephalon
- optic cup/nerves
- thalamus
- hypothalamus
- maxillary body
- part of 3rd ventricle
46
Derivatives of the metencepahlon
Pons
| Cerebellum
47
Derivatives of the myencephalon
Medulla oblongata
48
Nerves that derive from the telencephalon
Olfactory (I)
49
Nerves that derive from the diencephalon
Optic (II)
50
Nerves that derive from the mesencephalon
Oculomotor (III)
| Trochlear (IV)
51
Nerves that derive from the metencephalon and myelencephalon (hindbrain)
```
Trigeminal (V)
Abducens (VI)
Facial (VII)
Acoustic (VIII)
Glossopharyngeal (IX)
Vagus (X)
Hypoglossal (XI)
```
52
The spinal cord develops from
The caudal portions of the neural tube
53
The neural canal in this region will become the
Central canal of the spinal cord
54
When does the spinal cord develop and by what
- between the 4th and 20th week
| - by neuronal cell proliferation along the neural canal
55
Neuronal cell proliferation along the neural canal migrate peripherally to form what
Four longitudinal plates, which will become the gray matter of the spinal cord
56
A pair of anteriorly located cell masses, which constitute the basal plates will develop into the
Ventral horns of spinal cords
57
A pair of posterior located masses- the alar plates which will beceom the
Dorsal horns of the spinal cord
58
The basal and alar plates are separated by a longitudinal groove called the
Sulcus limitans
59
The portion of the spinal cord called the _________ originates from the interface of the alar and abasal plates and will become
Sympathetic nervous system
60
Anterior horn motor neurons innervate skeletal muscle and are classified as
Somatic efferent (SE)
61
The lateral horn motor neurons project to autonomic ganglia and are classified as
Visceral efferent
62
The ___ and ____ are distinct longitudinal cell columns in the gray matter of the spinal cord
Somatic efferent and the visceral efferent
63
The _____ runs the full length of the spinal cord
SE (somatic efferent)
64
The ___ column extend form T1 through L2 where it is called the intermediolateral cell column, and from S2through S where it is called the sacral visceromotor nucleus
VE (visceral efferent)
65
Neurons of the alar plate receive the central processes of developing
Posterior root ganglion cells
66
Sensory neurons whose peripheral processes innervate the skin and receptors in joint capsules, tendons, and muscles are classified as
Somatic afferent (SA)
67
Those that innervate receptors in visceral structures, such as the stomach, are classified as
Visceral afferent (VA)
68
Th physical relationship of the spinal cord to the vertebral column changes with what
The development of the fetus
69
By the end of the ________ the spinal nerves exit at about right angles to the spinal cord
First trimester
70
As development continues, which grows faster, the spinal cord or the vertebral column?
Vertebral column, the result is that the cord seems to be drawn rostrally by its attachment to the brain
71
The intervertebral foramina, containing the spinal nerves, move caudally; and the nerves form the lumbar, sacral, and coccygeal levels are lengthened to form a bundle called the
Cauda equina
72
Paired blocks of paraxial mesoderm
Somites
73
What do somites subdivide into
Sclerotomes, myotomes and dermatomes that give rises to the vertebrae, rib cage, and part of the occipital bone; skeletal muscle, cartilage, tendons, and skin
74
What does the brainstem consist of
Myelencephalon (medulla oblongata), the pons (part of metencephalon), and the mesencephalon (midbrain)
75
The central canal of the brainstem opens into where
Fourth ventricle
76
Where do the alar plates of the brainstem rotate
Dosrolaterally
77
Dorsolateral Rotation of the alar plates results in
A medial and lateral orientation of motor (basal plate) to sensory (alar plate) areas of the developing brainstem
78
During brainstem development, the _______ which disappears in the spinal cord during development, is retained
Sulcus limitans
79
What does the basal plate in the brainstem give rise to
Motor cranial nerve nuclei, viscerally efferent motor neurons
80
What does the alar plate in the brainstem give rise to
Sensory cranial nerve nuclei
81
Visceral efferent motor neurons provide preganglionic ___________ innervation to peripheral ganglia that serve visceral structures
Parasympathetic
82
What does the cerebellum arise from
Rhombic lip
83
What part of the rhombic lip forms the cerebellum
Rostral part
84
What does the rhombic lip join to form the cerebellar plate
Joins dorsal to the developing fourth ventricle
85
During __________, fissures appear that divide the cerebellum into its main lobes
Histogensis of the cerebellar cortex
86
Order of cerebellar fissures
Posteriolateral fissure then primary fissure
87
What divides the cerebelli into anterior and posterior lobes?
Primary fissure
88
What does the ventricular system develop from
Lumen of cephalopod portions of the neural tube
89
What beceoms the lateral ventricles
Telencephalic vesicles
90
What becomes the third ventricle
Telencephalic cavity
91
What does the cavity of the mesencephalon become
The cerebral aqueduct connecting the third and fourth ventricle and the opening between the lateral ventricles and the third ventricle become the interventricular foramina
92
That does the rhombencephalic cavity become
Fourth ventricle
93
What does the diencephalon become
Thalamus and hypothalamus
94
When are telencephalic vesicles formed
End of 5th week
95
What are all of the part of the telecephalon that develop at end of fifth week
- future cerebral cortex and white matter
- olfactory bulb and tract
- portions of the basal nuclei
- the amygdala and the hippocampus
96
What does the diencephalon develop into
```
The thalamus nuclei
Optic cup (future retina and CNII)
```
97
Where do CNS neuro blasts arise at
The luminal surface of the neural tube, they cluster at the ventricular surface
98
As cells undergo their last division, they begin to migrate away from the luminal (ventricular) surface on transient glial cells called
Radial glia
99
Inside out pattern of development
- After radial glia migrate and postion in brain, extend processes and form connections.
- in cerebral cortex the first cells to migrate will disembark from radial glia and take up positions close to the ventricular surface
- neuro blasts migrate along radial glia, force their way through the differented cell layers to take up positions progressively closer to the pial surface
100
How do neurons find their targets
- neuronal targets secret trophic factors, signpost molecules, recognition molecules, N-CAMs act on atonal growth cone
- growth cone is expanded part of tip f growing axon
- cont sends out small extensions (filopodia)
- some are stabilized as they find proper molecules and others retract
- determines the direction of further growth
101
The sensory neurons of dorsal root ganglia are derived from
The neural crest
102
The segmental nature of the embry is reflected in the segmental sensory innervation of the body surface, this is known as
Dermatomes
103
Failure of the anterior neuropore to close
Anencephaly
104
What does anencephaly result in
No brain formation
Freq is 1:5,000
Death inevitable
105
Failure of the back of the skull to close
Cranioshisis
106
Usually there is a herniation of intracranial contents through the skull
Cranium bifidum
107
The cystic structure contains the meninges
Meningocele
108
Meninges plus brain in a cystic structure
Meningeoencephalocele
109
Meninges plus brain and a part of the ventricular system in the cystic structure
Meningohydroencephalocoel
110
Herniation of the cerebellar vermis and tonsils through the foramen Magnus
Chiari I malformation
111
Often associated with a cavitation of the spinal cord to of the medulla
Chiari I malformation
112
Similar defect as chiari I but associated with myelomeningocele
Chiari II malformation (Arnold- Chiari)
113
Pathophysiology of Chiari II malformation
Increased cause pressure on the medulla oblongata and cervical spinal cord
114
Presentation of chiari II malformation
- segmental amyotrophy and sensory loss, pain
- stridor and poor swallowing
- bilateral vocal cord paralysis, platybasia, and aqueductal narrowing
115
Dilation of the fourth ventricle secondary to atresia of the foramina of Luscshka and Magendie, hypoplasia of the midline portion (vermis) of the cerebellum and enlargement of the posterior fossa
Dandy walker
116
Patients often present with development delay, enlarged head circumference, and signs and symptoms of hydrocephalus
Dandy walker
117
Diagnosis of dandy walker
MRI, CT showing an enlarged posterior fossa with a midline cyst
118
Treatment of dandy walker
Shunt in teat hydrocephalus and prevent herniation
119
This disorder causes myeloschisis-defect in the closure of the posterior neuropore
Spina bifida
120
Always involves a failure of the vertebral arches to close
Spina bifida
121
This type of spina bifida the skin is intact. The site of the defect is usually marked by a patch of hairs
Spina bifida occulta
122
This type of spina bifida th skin is not closed over the vertebral defect
Spina bifida aperta
123
Spina bifida +meninges and CSF+neural tissue the neural tissue may be the lower part of the spinal cord or cauda equina
Meningomyelocele
124
Spina bifida+meninges and CSG
Meningocele
125
Symptoms of spina bifida
Infants with meningomyelocele may be unable to move they lower limbs or may not perceive pain
126
Diagnosis of spina bifida
Amniocentresis revlease increased alpha-fetoprotein levels in amniotic fluid
127
Prevention of spina bifida
-folic acid
128
What are some drugs that can cause dysraphic defects
Drugs for epilepsy such as valproic acid and carbamazepine
129
Failure of PNS ganglion cell from the neura crest
Hirschpriung disease
130
Who is Hirschprung disease dominant in
Male, some Downs
131
Presentation of Hirschprung disease
- absence of ganglion cells in meissner submucosal plexus and Auerbach myenteric plexus
- constant contraction without relaxation results in obstruction
- proximal uninvolved bowl is dilated by has peristalsis
132
Clinical findings of Hirschprung disease
- abdominal pain
- chronic constitution
- absent stool on examing finger
- alternating signs of obstruction with diarrhea
133
Complications of Hirschprung disease
Enterocolitis of dilated bowl (danger of perforation), which is most common cause of death
134
Diagnosis of Hirschprung disease
X-ray and rectal biopsy
135
Treatment of Hirschprung disease
Surgical resection of affected segment
136
The differentiation of prosencephalon into the diencephalon and telencephalon
Prosencephalization
137
Failure of the prosencephalon to undergo cleavage results in this
Holoprosencephaly
138
Most severe form of holoprosencephaly. No lobes. Single forebrain ventricle, the thalamus is poorly developed, and many structures are lacking
Alobar holoprsoencephaly
139
Some seaparation of the forebrain, partial development of the falx cerebri, some visible lobes and gyri, rudimentary and enlarged lateral and third ventricles continuous one with the other, and septum pellucidum, that normally separate the ventricles are missing
Semilobar holoprosencephaly
140
Most infants with holoprosencephaly
Have facial malformations-hypotelorism or single midline eye (cyclops) accompanied by a rudimentary nasal structure (proboscis)
141
Defects of prosencephalization are associated with
Alcohol
Retinoic acid
Genetic anamolies (trisomy 13 and 18)
142
No gyri formed
Lissencephaly
143
Excessive growth of gyri
Pachygyria
144
Fecieicnt growth of gyri
Micorgyria
145
Symptoms of fetal alcohol syndrome
- short stature
- low body weight
- small head size
- hypertelorism
- smooth philtrum
- thin upper lip
- poor coordination
- low intelligence
- problems with hearing and seeing
146
Infections diseases causing congenital nervous system defects
- Toxoplasmosis (cerebral calcification)
- other agents (syphillis, HIV)
- rubella
- cytomegalovirus
- herpes simplex virus. HIV infection has alaos been associated with it
TORCH
147
Nervous system defects caused by infectious diseases
Cataracts, retinitis and blindness, deafnesss, cerebral atrophy, and microcephalic. Infants actively infected at birth can also have rash, fever, anemia, bleeding, and other organ system diseases
148
Flavivirus transmitted mainly by Aedes mosquitos
Zika
149
Initial outbreak of Zika
Associated with neurological complications such as Guillain-Barré syndrome, whihc coincided with ZIKV outbreaks
150
ZIKV in America has been associated with a striking increase in the number of reported cases of
Microcephaly in infants
151
What is known about the association between ZIKV infection and the development of severe neurological disorders
- microcephaly
- babies cry constantly, leading to breathing problems
- long term neural deficits and seizures
