Development of Nervous system

Question 1

Central nervous system

Answer 1

formed in week 3 as neural plate

neural plate -> neural tube -> brain and spinal cord

Question 2

Peripheral nervous system

Answer 2

derived from:

1. Neural crest cells: peripheral ganglia, Schwann cells, afferent nerve fibers
2. Neural tube: preganglionic autonomic fibers, fibers innervating skeletal muscle
3. Mesoderm: dura mater, CT around peripheral nerve fibers

Question 3

Development of neural tube

Answer 3

week 3-4

1. Neural plate: thickening of neural ectoderm
2. Neural groove: formed by neural plate folding
3. Neural fold: fuse in midline, neural crest differentation
4. Neural tube: neural folds fuse + separate from surface ectoderm

Question 4

Neural tube

Answer 4

• cranial part: brain
• caudal part: spinal cord
• cavity: central canal of spinal cord + ventricles
• anterior neuropore: lamina terminalis
• posterior neuropore

Question 5

Neural crest

Answer 5

gives rise to:

• pseudounipolar ganglion cells (spinal, cranial nerve ggl)
• Schwann cells
• Multipolar ganglion cells (autonomic)
• Leptomeninges
• Chromaffin cells of suprarenal medulla
• Pigment cells
• Odontoblasts
• Skeletal + connective components of pharyngeal arches
• Aorticopulmonary septum of heart
• Parafollicular cells

Question 6

Placodes

Answer 6

thickenings of cephalic surface ectoderm

1. Lens placode: lens, induced by optic vesicle
2. Nasal placode: olfactory nerve, induce formation of olfactory bulb
3. Otic placode: organ of Corti, spiral ggl, cristae amullares, maculae utriculi and sacculi, vestibular ggl, vestibulocochlear nerve

Question 7

Stages of neural tube development: primary brain vesicles

Answer 7

week 4

• proencephalon:otic vesicles, telencephalon+diencephalon
• mesencephalon
• rhombencephalon: metencephalon + myelencephalon
• cephalic flexure
• cervical flexure

Question 8

Stages of neural tube development: secondary brain vesicles

Answer 8

week 6

1. Telencephalon: cerebral hemispheres, olfactory bulb
2. Diencephalon
3. Mesencephalon: cerebral aqueduct
4. Metencephalon: rhomboic lips -> cerebellum, pons
5. Myelencephalon: medulla

Question 9

Cells of neural tube wall

Answer 9

neuroepithelial cells that gives rise to:

1. Neuroblasts: neurons in CNS
2. Glioblasts:
   - macroglia: astrocytes, radial glial cells, oligodendroglia
   - ependymal cells: ependymocytes, tanycytes, choroid plexus cells
3. Microglia

Question 10

Layers of early neural tube wall

Answer 10

1. Spinal cord:
   - ventricular zone(neurepith. layer): ependymal cells lining central canal, neurons and glial cells of spinal cord
   - intermediate zone(mantle layer): grey matter of spinal cord, alar and basal plates
   - marginal zone: white matter of spinal cord
2. Brain
   - ventricular zone: ependymal cells lining ventricles, neurons and glial cells of brain
   - intermediate zone: cerebral cortex, basal ganglia
   - marginal zone: molecular layer of cortex
   - cortex: grey matter of cerebral hemispheres

Question 11

Alar plate

Answer 11

dorsolateral thickening of intermediate zone of neural tube
gives rise to: sensory neuroblasts of dorsal horn
receives axons -> dorsal roots from dorsal root ganglion
becomes dorsal horn of spinal cord

Question 12

Basal plate

Answer 12

ventrolateral thickening of intermediate zone of neural tube
gives rise to: motor neuroblasts of ventral and lateral horns
axons exit from spinal cord and form ventral roots
becomes ventral horn of spinal cord

Question 13

Sulcus limitans

Answer 13

longitudinal groove in lateral wall of neural tube
appears week 4
separates alar ad basal plates
disappears in adult but remains in rhomboid fossa

Question 14

Position changes of the spinal cord

Answer 14

week 8 spinal cord length = vertebral canal
at birth conus medullaris to L3, in adult L1-L2
disparate growth results in caudal equina + filum terminale

Question 15

Development of Myelencephalon: Alar plates

Answer 15

Sensory neuroblasts give rise to:

• dorsal column nuclei
• inf. olivary nuclei
• solitary nucleus
• spinal trigeminal nucleus
• cochlear and vestibular nuclei

Question 16

Development of Myelencephalon: Basal plates

Answer 16

Motor neuroblasts give rise to:

• hypoglossal nucleus
• nucleus ambiguus
• dorsal nucleus of vagal nerve
• inf. salivatory nucleus

Question 17

Development of Myelencephalon: Roof plate

Answer 17

• forms roof of 4th ventricle
• is the tela choroidea
• invaginated by pal vessels -> choroid plexus

Question 18

Development of Methencephalon: Pons

Answer 18

1. Alar plate sensory neuroblasts:
   - solitary nucleus
   - vestibular and cochlear nuclei
   - spinal and principal trigeminal nuclei
   - pontine nuclei
2. Basal plate motor neuroblasts:
   - abducent nucleus
   - facial nucleus
   - motor trigeminal nucleus
   - sup. salivatory nuclei
3. Base of pons

Question 19

Development of Methencephalon: Cerebellum

Answer 19

formed by rhombic lips - thickened alar plates
cerebellar plates gives rise to:
- vermis
- cerebellar hemispheres
- 3 layer cortex
- external granular layer
- folia and fissures

Question 20

Development of Mesencephalon

Answer 20

1. Alar plate neuroblasts
   - superior and inferior colliculi
2. Basal plate neuroblasts
   - trochlear nuclei
   - oculomotor nuclei
   - substansia nigra
   - red nucleus

Question 21

Epithalamus

Answer 21

Diencephalon

• from embryonic roof plate and dorsal parts of alar plates
• gives rise to: pineal body, tela choroidea, choroid plexus of 3rd ventricle

Question 22

Thalamus

Answer 22

Diencephalon

• from alar plates
• gives rise to: thalamic nuclei

Question 23

Hypothalamus

Answer 23

Diencephalon

• from alar plate and floor plate
• gives rise to: hypothalamic nuclei, mammillary bodies, neurohypophysis

Question 24

Subthalamus

Answer 24

Diencephalon

• from alar plates
• gives rise to: neuroblasts -> globes pallidus

Question 25

Hypophysis

Answer 25

1. Anterior lobe: - from Rathke's pouch 2. Posterior lobe: - from ventral evagination of hypothalamus

Question 26

Development of Autonomic Nervous system

Answer 26

1. Sympathetic neurvous system: - from basal plate of neural tube and neural crest cells 2. Parasympathetic nervous system: - from basal plate of neural tube and neural crest cells

Question 27

Olfactory nerve

Answer 27

- from nasal placode - mediates smell - capable of regeneration

Question 28

Optic nerve

Answer 28

- from ganglion cells of retina - mediates vision - does not regenerate after transection

Question 29

Oculomotor nerve

Answer 29

- from basal plate of rostral midbrain | - ocular motility, pupillary constriction, accommodation

Question 30

Trochlear nerve

Answer 30

- from basal plate of caudal midbrain | - superior oblique m.

Question 31

Trigeminal nerve

Answer 31

- motor division from basal plate of rostral pons - sensory divison from cranial neural crest - sensory + motor innervation of 1st pharyngeal arch

Question 32

Abducent nerve

Answer 32

- from basal plate of caudal pons | - abduction of globe

Question 33

Facial nerve

Answer 33

- motor division from basal plate of pons - sensory division from cranial neural crest - sensory + motor innervation of 2nd pharyngeal arch

Question 34

Vestibulocochlear nerve

Answer 34

- from otic placode - vestibular - balance and equilibrium - cochlear - hearing

Question 35

Glossopharyngeal nerve

Answer 35

- motor division from basal plate of medulla - sensory division from cranial neural crest - sensory + motor innervation of 3rd pharyngeal arch

Question 36

Vagal nerve

Answer 36

- motor division from basal plate of medulla - sensory division from cranial neural crest - sensory + motor innervation of 4th and 6th pharyngeal arch

Question 37

Accessory nerve

Answer 37

- from basal plate of spinal segments C1-6 | - sternocleidomastoid m. and trapezius m.

Question 38

Hypoglossal nerve

Answer 38

- from basal plate of medulla | - intrinsic and extrinsic muscles of tongue

Question 39

Development of Choroid plexus

Answer 39

- from roof plates of rhombencephalon and diencephalon

Question 40

Ventral nerve roots

Answer 40

week 4 nerve cells in basal plates of spinal cord gets collected into bundles

Question 41

Dorsal nerve roots

Answer 41

originates from dorsal root ganglia central processes grow into the spinal cord distal processes join the ventral nerve roots to form spinal nerve

Question 42

Myelination of nerves

Answer 42

4th month Schwann cells (from neural crest) myelinated peripheral nerves -> neurilemma sheath Oligodendroglial cells myelinate nerve fibers in spinal cord

Question 43

Development of Telencephalon: Cerebral hemispheres

Answer 43

5th week Bilateral evagination of lateral wall of prosencephalon Corpus striatum: basal part of hemispheres grow + bulges into lateral ventricle Choroid plexus: hemisphere wall with single layer of ependymal cells + vascular mesenchyme Hippocampus: thickening of wall of hemisphere

Question 44

Development of Telencephalon: Cortex development

Answer 44

from pallidum- paleopallidum + neopallidum | Neopallidum: neuroblasts migrate to subpial position -> mature neurons

Question 45

Development of Telencephalon: Olfactory bulbs

Answer 45

Olfactory placodes from neural crest cells + ectoderm of frontonasal prominence Olfactory bulb from neural crest cells + floor of telencephalon Sensory neurons of nasal epithelium from cells in nasal placodes

Question 46

Development of Telencephalon: Commissures

Answer 46

Anterior commissure:lamina terminalis Hippocampal commissure: fibers from hippocampus -> converge on lamina terminalis Corpus callosum: week 10. Small bundle in lamina terminalis -> expands due to neopallidum Posterior + habenular Optic chiasma