Development of the Brain Flashcards

1
Q

When does the brain develop?

A

During the 3rd week

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2
Q

What does the brain develop from?

A

From the neural tube, cranial to 4th pair of somites

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3
Q

How do the primary brain vesicles form?

A

Fusion of neural folds in cranial region and closure of rostral/cranial neuropore

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4
Q

What are the primary brain vesicles?

A

Forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon)

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5
Q

What secondary vesicles does the prosencephalon give rise to?

A

Telencephalon and diencephalon

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6
Q

What secondary vesicles does the mesencephalon give rise to?

A

Mesencephalon

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7
Q

What secondary vesicles does the rhombencephalon give rise to?

A

Metencephalon and myelencephalon

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8
Q

What does the telencephalon give rise to?

A

Cerebral hemispheres and lateral ventricles

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9
Q

What does the diencephalon give rise to?

A

Thalami (hypothalamus, epithalamus, thalamus) and 3rd ventricle

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10
Q

What does the mesencephalon give rise to?

A

Midbrain and aqueduct

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11
Q

What does the metencephalon give rise to?

A

Pons and cerebellum and upper part of 4th ventricle

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12
Q

What does the myelencephalon give rise to?

A

Medulla and lower part of 4th ventricle

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13
Q

What causes brain folding/flexures?

A

Unequal proliferation in different brain vesicles

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14
Q

What is the first flexure to fold?

A

Midbrain flexure (mesencephalic flexure). Flattening/face down forward motion of telencephalon and diencephalon at junction with mesencephalon

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15
Q

What is the second flexure to fold?

A

Cervical flexure. Forward bending at hindbrain/spinal cord junction creates positioning of brainstem underneath brain

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16
Q

What is the third flexure?

A

Pontine flexure. Folds backward at metencephalon/myelencephalon junction. Positions cerebellum over/posterior to pons

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17
Q

What forms in the caudal myelencephalon?

A

Nuclei gracilus and cuneatus (from alar plate)

Pyramids (basal plate)

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18
Q

What forms in the rostral myelencephalon?

A

Alar plates (sensory/afferent inputs) and basal plates (motor/efferent outputs)

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19
Q

How does the pontine flexure move the alar and basal plates?

A

Alar plate moves lateral to basal plate

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20
Q

Neuroblasts in the basal plate develop into what?

A

Efferent neurons

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21
Q

Neuroblasts in the alar plate develop into what?

A

Afferent neurons

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22
Q

How are the olivary nuclei formed?

A

Alar neurons migrate anteriorly

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23
Q

How does the cerebellum develop?

A

From the dorsal parts of alar plates. Cerebellar swellings arise which fuse over the median plate, overgrowing the posterior side of the 4th ventricle

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24
Q

How does the choroid plexus form? (specifically in 4th ventricle)

A

Initially has a basic organization (pia + ependymal roof) without invaginations/layering called tela choroidea on roof of 4th ventricle. Then invaginates into 4th ventricle to form choroid plexus

25
Q

How do the median/lateral apertures form?

A

The roof of the 4th ventricle ruptures/evaginates in 3 locations to permit CSF to enter subarachnoid space

26
Q

In the midbrain, what is the tectum?

A

Forms from neuroblasts of the alar plate migrating together. Then forms superior (vision) and inferior (auditory) colliculi

27
Q

In the midbrain, what are tegmental nuclei?

A

Form from neuroblasts of basal plates (red nuclei, reticular nuclei, CN III/IV nuclei)

28
Q

What are the cerebral peduncles in the midbrain?

A

Also known as the crus cerebri, extensions of white matter. Fiber tracts from cortex to rest of body.

29
Q

How is the cerebral aqueduct formed?

A

Narrowing of neural canal in the midbrain

30
Q

What is the substantia nigra?

A

Nucleus important for movement, unsure whether alar or basal derivative

31
Q

How are the thalami formed?

A

Swellings in lateral walls of 3rd ventricles form the thalamus, hypothalamus, and epithalamus

32
Q

What separates the thalamus and epithalamus?

A

Epithalamic sulcus

33
Q

What separates the thalamus and hypothalamus?

A

Hypothalamic sulcus

34
Q

What structure is present in people whose thalamus have fused?

A

Massa intermedia (interthalamic adhesion/mass) connects R and L thalamic structures in 70% of people

35
Q

How is the hypothalamus formed?

A

Arises from neuroblasts in intermediate zone. Mammillary bodies form on the anterior surface

36
Q

Where does the pineal gland come from?

A

From the epithalamus

37
Q

How does the epithalamus form?

A

From roof/posterior portion of lateral wall of 3rd ventricle

38
Q

What does the pineal gland do?

A

Regulates sleep/wake cycles

39
Q

What is the infundibulum?

A

Attaches the posterior pituitary to the hypothalamus

40
Q

How is the anterior pituitary made?

A

Upgrowth of surface ectoderm from roof of stomodeum called the hypophyseal diverticulum (Rathke’s pouch)

41
Q

How is the posterior pituitary made?

A

Downgrowth of diencephalon (neuroectoderm) called the neurohypophyseal diverticulum

42
Q

When does the pituitary gland develop?

A

3rd week

43
Q

When does the connection of the anterior pituitary to the oral cavity degenerate?

A

6th week

44
Q

What does the telencephalon divide into?

A

Two telencephalic/cerebral vesicles which then make the cerebral hemispheres

45
Q

What happens after rostral neuropore closes?

A

Optic vesicles appear

46
Q

Where does the falx cerebri come from?

A

Mesenchyme is trapped in the longitudinal fissure when cerebral hemispheres expand and meet each other in the midline

47
Q

What is holoprosencephaly?

A

Failure of telencephalon to divide into R/L cerebral vesicles (single-lobed brain). Impairs cholesterol synthesis and therefore SHH signaling

48
Q

What are commissures?

A

White matter tracts that connect different brain regions to each other (ex: corpus callosum)

49
Q

Where do commissures form?

A

In the lamina terminalis (rostral/inferior end of forebrain)

50
Q

What do anterior commissures connect?

A

R and L olfactory areas

51
Q

What do hippocampal commissures connect?

A

R and L hippocampi

52
Q

What do posterior commissures connect?

A

R and L temporal lobes

53
Q

What does the corpus callosum connect?

A

R and L hemispheres

54
Q

What is the septum pellucidum?

A

A thin plate of brain tissue that separates R and L lateral ventricles

55
Q

How does postnatal growth of the brain occur?

A

Neurons increasing in size and myelination of axons

56
Q

How does the cortex grow?

A

New neurons migrate through deeper layers to exit to the surface and establish more superficial layers (‘inside out’ development)

57
Q

What is lissencephaly?

A

Abnormal migration of new neurons onto surface. Smooth brain = decreased gyration of brain. Developmental and mental abnormalities and seizures

58
Q

What is microcephaly?

A

Calvaria and brain are underdeveloped