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Y2 - CNS > Lecture 2 - Development Of CNS > Flashcards

Lecture 2 - Development Of CNS Flashcards

1
Q

What is gastrulation?

A

The process where the bilaminar disc becomes the trilaminar disc

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2
Q

Briefly describe the process of gastrulation:

A

Outer layer of the bilayer germ disc invaginates at the primitive streak to produce a three layered germ disc

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3
Q

What are the 3 layers of the trilaminar disc?

A

Ectoderm
Mesoderm
Endoderm

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4
Q

What are some derivatives of the ectoderm?

A

Skin
Neural tissue and neural crest

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5
Q

What are the derivatives of the mesoderm?

A

Heart,vessels and muscles
Notochord (made of endoderm)

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6
Q

What are the derivatives of the endoderm?

A

Digestive and respiratory tracts

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7
Q

What is the function of the notochord?

A

Induces neuraltion

Induces the neural plate of ectoderm above it to start to fold in on itself to generate the neural tube = neurulation

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8
Q

What is notogenesis?

A

Formation of the notochord

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9
Q

Briefly describe notogenesis (formation of the notochord):

A

Made from the primitive node and migrates to form a rod like structure in the mesoderm during gastrulation

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10
Q

What is neuralation?

A

Formation of the neural tube

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11
Q

What structure induces neuraltion?

A

Notochord

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12
Q

What happens in neuraltion?

A

Notochord and paraxial mesoderm send signals to the overlying ectoderm causing it to thicken forming the neural plate
Neural plate thickens and begins to fold forming neural folds
Neural folds elevate and fuse in the midline at mid cervical level;
Neural crest cells detach and migrate

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13
Q

What way does the neural tube zip up/fuse?

A

Rostrally and caudally (pinches in the middle then moves rostrally and caudally)

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14
Q

What condition is caused if the neural tube fails to fuse in the rostral direction?

A

Anencephaly

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15
Q

What is anencephaly?

A

When the brain doesn’t form at all

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16
Q

What condition can be caused by failure of the neural tube to fuse in the caudal direction?

A

Spina bifida

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17
Q

How many main swellings form at the rostral neural tube?

A

3

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18
Q

What are the 3 main swellings from the rostral neural tube which become major parts of the adult brain?

A

Prosencephalon
Mesencepohalon
Rhombencephalon

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19
Q

What structures form from the prosencephalon, mesencephalon and Rhombencephalon?

A

Prosencephalon = forebrain
Mesencephalon = midbrain
Rhomencephalon = hind brain (4th ventricle that comes from this region is shaped like a rhombus)

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20
Q

Which of the 3 main swellings from the rostral neural tube are further subdivided into 2 swells?

A

Prosencephalon and Rhombencephalon

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21
Q

What does the prosencephalon subdivide into?

A

Telencephalon
Diencephalon

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22
Q

What does the rhombencephalon get subdived into?

A

Metencephalon
Myelencephalon

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23
Q

What forms fromt he telencephalon?

A

Most of the cerebral hemisphere

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24
Q

What forms from the diencephalon?

A

Thalamus
Hypothalamus
Optic nerve/retina

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25
Q

What is the function of the mesencephalon?

A

Boundary between fore and hindbrain

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26
Q

What does the metencephalon form?

A

Pons and cerebellum

Meta analysis happens after main research and pons and cerebellum sit behind or after the cerebrum

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27
Q

What does the myelencephalon form?

A

Medulla

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28
Q

What are the functions of the signals that the notochord produces during neuraltion?

A

Are BMP-4 inhibitors so causes ectoderm cells to proliferate

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29
Q

Generally, what part of the brain has the motor structures and what part of the brain has the sensory structures?

A

Motor = anterior (motor forwards)

Sensory = posterior (think occipital lobe for sight is posterior)

30
Q

What structure determines the orientation of the brain and the spinal cord so that motor structures are anterior and sensory structures are posterior?

A

Notochord

31
Q

What does the notochord produce to determine the orientaion of the brain and spinal cord structures?

A

Morphogens

32
Q

What affect does the notochord have on the neural tube due to the morphogens?

A

Produces sonic hedgehog so that the cells of the spinal cord nearest to it becomes the ventral side

33
Q

What does the ectoderm produce to stimulate dorsal fate?

A

BMP

34
Q

What does the notochord stimulate the ventral portion of the neural tube/spinal cord to produce?

A

Basal/floor plate which gives rise to motor neurones

35
Q

What forms in the dorsal portion of the neural tube in absence of influence of the notochord?

A

Alar/roof plate which gives rise to the sensory neurones

36
Q

What roots are sensory and what roots are motor in the nervous system?

A

Sensory = dorsal root
Motor = ventral root

37
Q

What neurones are found in the dorsal and ventral horns of the spinal cord?

A

Dorsal horn = sensory neurones

Ventral horn = motor neurones

38
Q

How are the dorsal columns and the motor corticospinal tract postioned in the spinal cord?

A

Dorsal columns posterior

Corticospinal tract anterior

39
Q

What forms from the neural tube central canal?

A

Brains ventricular system

40
Q

What reflex is the superior colliculus important in?

A

Visual reflex’s

41
Q

What reflex is the inferior colliculi important in?

A

Auditory reflex

42
Q

How are the sensory alar and motor basal plates arranged in the neural tube at the brainstem?

A

Motor basal plates more medial close to canal and alar sensory more lateral

43
Q

On a basic level how does the cauda equina form?

A

Initially cord fills entire vertebral canal
But as you get to L1 vertebra begin to grow faster than the spinal cord this stretches the lower portion of the cord producing the cauda equina

44
Q

What is hydrocephalus?

A

Dilation of the ventricles of the brain due to occlusion leading to build up of CSF

45
Q

How can neural tube defects predispose to hydrocephalus?

A

Cord gets tethered at site of defect
Spine grows and cord cant move within the vertebral canal so the brainstem containing the 4th ventricles gets pulled down through Foramen magnum becoming occluded so CSF builds up

46
Q

What condition is caused by failure to close the neural tube in the cranial direction?

A

Anencephaly

47
Q

What condition is caused by the failure of closure in the caudal direction (involves the spine/spinal cord)?

A

Spina bifida

48
Q

What structure is failing to develop when the neural tube fails to zip up/fuse in the cranial or caudal direction?

A

Posterior vertebral arches

49
Q

What is craniorachischisis?

A

Most severe neural tube defect where the tube completely fails to fuse both cranially and caudally

It is embryonically fatal since neither brain or spinal cord forms

50
Q

What are some conditions caused by failure of the cranial neuropore to fuse?

A

Anencephaly
Cranial bifida
Cranial meningocele

51
Q

What are the 4 main neural tube defects caused by failure of the caudal neuropore to fuse?

A

Spina bifida occulta
Spina bifida cystica
Meningocele
Myelomeningocele

52
Q

Which neural tube defect involves the h spinal cord and so has neurological problems and which defect doesn’t?

Meningocele or myelomeningocele

A

Meningocele doesn’t involve spinal cord only meninges

Myelomeningocele involves spinal cord

53
Q

What is myelocele?

A

Spinal cord fails to develop so the lumen of the neural tube is exposed to the outside world and is associated with a CSF filled cyst

54
Q

Why are children with myelocoele at risk to meningitis and have neurological deficits?

A

Spinal cord doesn’t form properly

Neural tissue is exposed to the world

55
Q

What is a Myelomeningocele?

A

CSF fillled cyst containing the spinal cord (meninges and neural tissue)
The vertebral body doesn’t fully close

Child will likely have neurological deficits

A type of spinal bifida cystica

56
Q

What is a meningocele?

A

Presence of a CSF fille cyst that contains only the meninges

Type of spinal bifida cystica

57
Q

How does myelomeningocele and meningocele present differently?

A

Meningocele transilluminates very well whereas Myelomeningocele doesn’t

Meningocele normally has good neurological prognosis whereas Myelomeningocele doesn’t

58
Q

What are the 2 types of spina bifida c ystica?

A

Meningocele
Myelomeningocele

59
Q

What is it called when the meninges herniate out of the fontanelles of the skull?

A

Cranial meningocele

60
Q

What is spina bifida occulta and how does it present?

A

Hidden spina bifida where the vertebral arches fail to fuse

Site has an overlying tuft of hair and nothing else is really affected

61
Q

How do you prevent neural tube defects?

A

Take folic acid 400mg daily from 3months before conception until week 12 of pregnancy

62
Q

What other structure can folate deficiency lead to anomalies in except neural tube defects?

A

Palatial anomalies

63
Q

What are neural crest cells?

A

Cells at the Lateral border that during neuraltion dissociates from their neibouring cells to form neural crest cells (they migrate from the neural tube)

64
Q

What cells are derived from neural crest cells?

A

All neurones who’s cell bodies are in the PNS:
-primary sensory neurones
-autonomic postganglionic neurones
-enteric neurones

Schwann cells
Cells of adrenal medulla
Meloncytes
Leptomeninges
Head mesenchyme

65
Q

What are the leptomeninges?

A

Arachnoid and pia mater

66
Q

What tissue receives significant contribution from neural crest?

A

Thymus
Thyroid
Spiral septum of heart
Parts of teeth

67
Q

Where do neural crest cells migrate from in the embryo?

A

Dorsal part

68
Q

As neural crest cells migrate dorsal to ventral what structures do they leave behind?

A

Dorsal root ganglia
Sympathetic ganglia
Preaortic ganglia (receive input from splanchnic nerves)
Adrenal medulla (chromaffin cells)
Gut wall enteric nervous system

69
Q

What are the 2 main neural crest cell defects?

A

Hirschsprungs disease
Di George Syndrome

70
Q

What is Hirschsprung’s disease?

A

Neural crest cell defect

Lack of enteric nerves in sections of large intestine leading the Denervation of smooth muscle causing hypomotility and constipation

71
Q

What is Di George syndrome?

A

Neural crest cell defect

Immunodeficiency due to involvement of thymus (neural crest cells have big contribution)
Facial anomalies (cleft/lip palate, low set ears, small jaw)
Heart anomalies
Hypocalcaemia (parathyroid involve

Y2 - CNS (21 decks)

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