Development of Nervous system

Question 1

Part of neural tube forming the brain extends up to which somites.

Answer 1

4th pair of somites

Question 2

Point at which neural tube first closes

Answer 2

Cervical region along 4th to 6th somite pairs

Question 3

Describe origin and destination of mantle layer of spinal cord

Answer 3

Originates from neuroblasts that form a layer around the neural epithelium
Destined to form gray matter

Question 4

Describe formation of layers of spinal cord

Answer 4

The neuroepithelial layer is formed by pseudostratified columnar neuroepithelial cells. These cells divide and some of them differentiate into neuroblasts.
Neuroblasts divide to form a layer around the neural tube called mantle layer
They then send out their fibers which form the marginal layer that will give rise to white matter

Question 5

By which week does neural tube have 3 layers?

Answer 5

Week 5

Question 6

How is sulcus limitans produced?

Answer 6

Differential thickening of neural tube wall

Question 7

Basal plate of neural tube gives rise to

Answer 7

Ventral and Lateral gray horns

Question 8

Function of roof and floor plates

Answer 8

act as pathways for decussating fibers and connect the plates on the opposite sides(basal and alar plates)

Question 9

True or false: Neuroblasts are a result of meiosis of neuroepithelial cells

Answer 9

False: Neuroblasts are a result of mitosis of neuroepithelial cells

Question 10

What temporary changes to neuroblasts undergo when they migrate to the mantle layer?

Answer 10

Become apolar and rounded

*NOTE: Permanently loose the temporary dendritic processes they once sent off to lumen of neural tube

Question 11

What type of neuron is a neuroblast?

Answer 11

multipolar

Question 12

Precursors of glial cells

Answer 12

Glioblasts

Question 13

How does the fate of glial cells change from when they are in the mantle layer and when they are in the marginal layer?

Answer 13

In the mantle layer, they differentiate into oligodendroblasts and astroblasts

In the marginal layer, they will differentiate into microlial

Question 14

Origin of ependymal cells

Answer 14

arise from neuroepithelial cells when they stop giving off neuroblasts and glioblasts, then they give rise to ependymal epithelium

Question 15

What type of neuron is a spinal ganglia

Answer 15

unipolar

Question 16

True or false: Spinal ganglia are initially bipolar, but processes fuse and they become unipolar

Answer 16

True

Question 17

Explain formation of sympathetic ganglia.

Answer 17

Cells from neural crest cells in the thoracic region migrate behind aorta and align themselves along developing spinal cord in groups connected by longitudinal nerve fibers. These form the ganglia along the spinal cord

Other neural crest cells go in front of the developing aorta to form preaortic ganglia

Other neural crest cells travel to organs to form organ ganglia.

Question 18

Difference between preganglionic and postganglionic fibers.

Answer 18

Preganglionic are myelinated but postganglionic nerves are not myelinated

Question 19

Origin of cortex and medulla of adrenal glands

Answer 19

cortex is from mesoderm

medulla is from ectoderm neural crest cells

Question 20

Difference in distribution of chromaffin cells in adults and embryos

Answer 20

Chromaffin cells are scattered throughout in the embryo, but in the adults, they are limited to the adrenal medulla

Question 21

Embryologic origin of postganglionic parasympathetic fibers

Answer 21

Postganglionic parasympathetic fibers come from post ganglionic ganglia which originate from neural crest cells

Question 22

when does myelination begin?

Answer 22

month 4

Question 23

Why do spinal nerves run obliquely from spinal cord to vertebrae levels?

Answer 23

Due to disproportionate growth in IUL. After month 3, the vertebra and pia mater extend much faster than the spinal cord itself

Question 24

Explain changes in the length of the spinal cord at various stages.

Answer 24

At month 3, it reaches C1
By end of month 5, it reaches S1
By birth, it reaches L3

Question 25

Causes of neural tube defects

Answer 25

1. Hypervitaminosis for Vit A 2. Hyperthermia or hypothermia 3. Valproic acid (an anticonvulsant) 4. Folic acid/ vit B9 deficiency

Question 26

Diagnosis of neural tube defects

Answer 26

elevated levels of alpha fetoprotein in amniotic fluid or mother's serum ultrasonography

Question 27

Spina bifida

Answer 27

nonfusion of vertebral arches

Question 28

Enumerate SPINA BIFIDA OCCULTA

Answer 28

Neural tissue not affected Defect covered by skin with tuft of hair Usually occurs at level of L5 to S1 Asymptomatic

Question 29

Explain Spina bifida with meningocele

Answer 29

protrusion of meninges with CSF Can be easily fixed with surgery and child doesn't usually have symptoms 2. Spina bifida with meningomyelocele protrusion of meninges and spinal cord or nerve roots (is more common and severe) Symptoms include: paralysis, sensory loss below the sac and hydrocephaly Can be "treated" with surgery, but child will need special care

Question 30

Spina bifida with meningomyelocele

Answer 30

protrusion of meninges and spinal cord or nerve roots (is more common and severe) Symptoms include: paralysis, sensory loss below the sac and hydrocephaly Can be "treated" with surgery, but child will need special care

Question 31

The most severe spina bifida

Answer 31

Myeloschisis - nerve tissue is fully bare and a dermal or meningeal covering is absent

Question 32

Absence of spinal cord

Answer 32

Amyelus

Question 33

myelocystomeningocele

Answer 33

spinal cord dilates also called syringomyelocele

Question 34

Anencephaly

Answer 34

neural folds do not fuse at cranial region. it's a type of spinal bifida. always fatal

Question 35

Rachischisis

Answer 35

entire spine does not close

Question 36

List order in which brain flexures appear

Answer 36

Midbrain Cervical Pontine Forebrain/Cepalic flexure

Question 37

Formation of corpus striatum

Answer 37

In month 2, bases of cerebral hemispheres thicken and extend download into foramina of monro

Question 38

Internal capsule divides the corpus striatum into?

Answer 38

Lentiform nucleus | Caudate nucleus

Question 39

When does brain get its characteristic sulci and gyri?

Answer 39

Final part of IUL

Question 40

Cerebral cortex develops from

Answer 40

PALLIUM | which is divided into neopallium and archipalleum

Question 41

Development of Olfactory bulb

Answer 41

interaction between neural crest cells and floor of telencephalon causes the floor to differentiate into the olfactory bulb

Question 42

The first commissure to appear is the

Answer 42

anterior commissure

Question 43

When does corpus callosum appear?

Answer 43

week 10

Question 44

Roof plate of diencephalon forms which structures?

Answer 44

Choroid plexus of 3rd ventricle | Pineal gland

Question 45

Which structure of diencephalon includes mamillary bodies?

Answer 45

Hypothalamus

Question 46

Which plate of diencephalon forms pars narvosa of pituitary gland?

Answer 46

alar plate's downward extension as the infundibulum

Question 47

Holoprosencephaly

Answer 47

loss of midline structures resulting in brain and face malformations Causes 1. excess alcohol intake 2. defect in SHH gene 3. lack of cholesterol synthesis required for SHH gene to influence its effects

Question 48

Schizencephaly

Answer 48

large clefts in cerebral hemispheres

Question 49

Most commonly affected bone in ossification defects of skull

Answer 49

occipital bone

Question 50

Meningoencephalocele

Answer 50

defect in occipital bone large enough so that part of the brain bulges through

Question 51

Meningohydroencephalocele

Answer 51

defect in occipital bone so that brain and ventricles protrude

Question 52

A mother goes for her ultrasound and the clinician notices hydramnios. What is a possible cause?

Answer 52

Fetus could be having anencephaly because they lack swallowing mechanism

Question 53

Aqueductal stenosis

Answer 53

obstruction of aqueduct of Sylvius leading to hydrocephalus

Question 54

Enumerate on the Arnold-Chiari malformation

Answer 54

defect of cerebellum in which there is caudal displacement and herniation through foramen magnum, or incomplete development of cerebellum are 4 types type 1: cerebellum protrudes into foramen magnum due to spina bifida cystica type 2: cerebellum and brain stem extend into foramen magnum type 3: most serious. cerebellum goes past foramen magnum and into the spinal cord type 4: incomplete cerebellum Can be asymptomatic if its type 1 Serious symptoms arise from type 2,3 and 4 most of the times accompanies spina bifida cystica

Question 55

Cerebellum forms from which structures

Answer 55

rhombic limbs which form cerebellar plates