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First year semester 2 > CNS embryology > Flashcards

CNS embryology Flashcards

1
Q

What is gastrulation?

A

the process during embryonic development that changes the embryo from a blastula with a single layer of cells to a gastrula containing multiple layers of cells

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2
Q

Following gastrulation are the 3 layers of germ cells?

A
  1. ectoderm = skin, nervous system
  2. mesoderm = bone, kidney, blood, heart, muscle
  3. endoderm = gut, liver, lungs
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3
Q

Following gastrulation are the 3 layers of germ cells?

A
  1. ectoderm (outer layer) = skin, nervous system
  2. mesoderm = bone, kidney, blood, heart, muscle
  3. endoderm (innermost) = gut, liver, lungs
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4
Q

How is the neural tube formed?

A
  1. Ectoderm (outer layer) thickens to form the neural plate
  2. neural plate then starts to fold inwards, forming neural groove
  3. join = neural tube = CNS, brain and spinal cord
  4. Some neural ectoderm cells migrate from lateral margin to from nerual crest
  5. surface ectoderm = skin
  6. peripheral
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5
Q

How is the neural tube formed?

A
  1. Ectoderm (outer layer) thickens to form the neural plate
  2. neural plate then starts to fold inwards, forming neural groove
  3. join = neural tube = CNS, brain and spinal cord
  4. Some neural ectoderm cells migrate from lateral margin to from nerual crest
  5. surface ectoderm = skin
  6. peripheral NS = neural tube and crest
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6
Q

What are the 3 layers once the neural tube closes?

A
  1. Ventricular zone
  2. Mantle layer
  3. Marginal layer
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7
Q

How does the neural tube close?

A
  1. it progresses rostrally and caudally from the cervical region
  2. Rostral neuropore closes first at several sites - rapid dev of early brain vesicles
  3. caudal closure forms most of spinal cord. complete by about 28 days
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8
Q

What are the 3 layers once the neural tube closes?

A
  1. Ventricular/ germinal zone = inner
  2. Mantle layer = middle layer = grey matter
  3. Marginal layer = external surface = white matter
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9
Q

How does the rostral end of the neurotube develop after the 3 vesicles

A
  1. 5 vesicles

2. 2 vesicles: 2 additional swellings from prosencephalon = Telencephalon that form the cerebral hemispheres

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10
Q

How does the rostral end of the neurotube develop initially?

A
  1. rapidly after closure
  2. 3 vesicles: rostrally to caudally:
    a) prosencephalon (forebrain)
    b) Mesencephalon (mid brain)
    c) Rhombencephalon (hindbrain)
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11
Q

How does the rostral end of the neurotube develop after the 3 vesicles

A
  1. 5 vesicles
  2. 2 additional swellings from prosencephalon = Telencephalon that form the cerebral hemispheres. P also divides into diencephalon = thalamus and hypothalamus
  3. Mesencephalon doesn’t undergo further subdivision
  4. Rhombencephalon gives rise to metencephalon = pons and cerebellum and myelencephalon = medulla oblongata
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12
Q

What does flexures of the brain mean, whihc occurs during development?

A
  1. folds so that can fit more easily into a limited space in the cranial bulb
  2. mid brain flexure
  3. cervical flexure: junction between brain and spinal cord
  4. pontine flexure = pons
  5. Flexures straighten out in the adult animal
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13
Q

Neural tube closure defects rostral

A
  1. less common than cuadal
  2. Anencephaly = no forebrain
  3. Meningo(encephalo)cele = protuding meninges and neural tissue
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14
Q

Caudal neural tube closure defects

A 
More common than rostral
Often genetic
Seen most commonly in tailess breeds
1. Spina bifida
a) meningo(myelo)cele
b) Tethered cord syndrome
2. Rachischisis = failure of closure = open neural tube
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15
Q

How is neural cell differentiation controlled?

A
  1. Ventral neural tube is patterned by sonic hedgehog (SHH) secreted from the notochord and floor plate.
  2. Dorsal neural tube is patterned by bone morphogenetic protein signals (BMPs) secreted from the superficial ectoderm (and derived neural crest cells) and roof plate.
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16
Q

What induces neural tube formation

A
  1. notochord

2. done by producing signalling molecule called sonic hedgehog

17
Q

What leads to functional differences in dorsal vs ventral regions of the spinal chord?

A
  1. notochord = sonic hedgehog
  2. overlying ectoderm = BMPs
  3. Together these induce dorsal ventral patterning of neural tube
  4. indude secondary signals in neural tube itself
  5. Get gradient of signalling molecules = differential expression of transcription factors which control gene expression
  6. Ultimately leads to functional differences in dorsal VS ventral regions
18
Q

What does the neural cell differentiation result in?

A
  1. Dorsal half = alar plate = sensory pathways = inputs from peripheral nervous system
  2. Ventral = basal plate = motor = sends axons out into peripheral NS
19
Q

How does the spinal cord develop?

A
  1. Neural cavity becomes central canal, lines by ependyma cells
  2. alar and basal plates grow, not floor and for plate = symmetrical right and left sides
  3. Mantle = grey matter = dorsal and ventral horns which are separated by intermediate grey matter
  4. marginal = white matter = dorsal, lateral and ventral funicules
20
Q

What deos white and grey matter consist of?

A
  1. White consists of myelinated axons

2. grey consists of neuronal cell bodies and some unmyelinated axons

21
Q

How is the white matter split. and what are these bundles of?

A
  1. split into regions called funiculi, separated by motor and sensory roots
  2. bundles of axonal fibres which project rostrally/ cranially OR caudally
  3. Dorsal funiculus (dorsal column) contains sensory fibres, lateral = mixed sensry and motor and ventral = motor fibres
22
Q

How is grey matter structured?

A
  1. Split into horns
  2. Dorsal horn = receiving zone for axons of both somatic and visceral sensory (afferent) neurons
  3. Cell bodies reside in dorsal root ganglion
  4. Lateral horn contains cell bodies of preganglionic autonomic motor neurones (visceral efferents)
  5. ventral horn = site of cell bodies of somatic motor (efferent) neurones
23
Q

Pons and medulla development

A
  1. Alar plates move laterally (sensory)

2. motor parts move medially

24
Q

What are the species development in cerebellar development?

A
  1. depends on how developed species is at birth
  2. precocial species (hrose, cow, sheep) = well developed cerebellum = good motor function
  3. Altricial species (cat, dog humans) = poor motor function
25
Q

DEvelopment of midbrain

A
  1. neural cavity becomes mesencephalic aqueduct
  2. alar plates form rostral and caudal colliculi = visual and auditory reflexes
  3. basal plate = medial = ocilomotor (III) and trochlear (IV) nerve that innervate msucles that mvoe eye
26
Q

Development of forebrain

A
  1. formed from alar plate
  2. Diencephalon:
    a) roof of neural cavity expands, choroid plexus develops to form 3rd ventricle
    b) Floor: gives rise to neurohypophsis (pituitary)
    c) mantle forms thalamus and hypothalamis
    d) optic nerve from outgrowth of wall of thalamus
27
Q

Cerebral development

A
  1. telencephalic vesicles
  2. bilateral hollow outgrowths, grow out rostrally, curve caudally and ventrally
  3. forms cerebral hemispheres. 2 make up cerebellum
  4. The cavity of each outgrowth forms lateral ventricle, communicated with 3rd via intraventricular foramen
28
Q

List the 3 vesicle stage in embryonic development

A
  1. Prosencephalon (forebrain)
  2. Mesencephalon (midbrain)
  3. Rhombencephalon (hindbrain
29
Q

List the 5 vesicle stage of embryonic development

A
  1. Prosencephalon –> Telencephalon and Diencephalon
  2. Mesencephalon = M
  3. Rhombencephalon –> Metencephalon and Myelencephalon
30
Q

Where do the following adult brain structures develop from?

  1. Cerebrum
  2. Thalamus
  3. Hypothalamus
  4. Midbrain
  5. Pons and cerebellum
  6. MEdulla oblongata
A
  1. Cerebrum = Telencephalon
  2. Thalamus = Diencephalon
  3. Hypothalamus = Diencephalon
  4. Midbrain = MEsencephalon
  5. Pons and cerebellum = Metencephalon
  6. MEdulla oblongata = Myelencephalon
31
Q

What are the associates cranial nerves with:

  1. Cerebrum
  2. Thalamus
  3. Hypothalamus
  4. Midbrain
  5. Pons and cerebellum
  6. MEdulla oblongata
A
  1. Cerebrum = I
  2. Thalamus = II
  3. Hypothalamus = II
  4. Midbrain = III and IV
  5. Pons and cerebellum = V
  6. MEdulla oblongata = VI- XII
32
Q

True of false?

  1. Nervous system develops from the endodermal layer of the embryo
  2. Neural plate induces formation of notochord
  3. Neural tube gives rise to CNS
  4. Neural crest gives rise to PNS
  5. Neural crest fuses to form neural tube
  6. Neural cells differentiate under control of a small number of evolutionary conserved signalling factors
  7. Structures of the adult forebrain arise from the most anterior part of the neural tube, the forebrain vesicle
A
  1. FALSE = from ECTOderm
  2. FALSE notochord induces formation of neural plate!
  3. TRUE
  4. TRUE - neural crest adn bit of neural tube give rise to PNS
  5. False - neural crest = 2 bits that come off and hang out dorso ventrally to neural tube = neural plate fuses to form neural tube
  6. TRUE - sonic hedge, BMPS
  7. True - forebrain = thalamus and cerebral hemisphere

First year semester 2 (50 decks)

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