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Neuroscience - spring 2024 > lec 3 - nervous system development > Flashcards

lec 3 - nervous system development Flashcards

1
Q

Pre-embryonic period

A

Begins with fertilization and ends at implantation

weeks 1 & 2

how embryo develops

before nervous system

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2
Q

Embryonic/Critical period

A

Characterized by cell differentiation and organogenesis

weeks 3-8

1st trimester = most sensitive - susceptible to environment toxins

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3
Q

Fetal period

A

Characterized by growth of fetus

weeks 9+

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4
Q

Pre-Embryonic Period: Week 1

A

Fertilization
Cleavage
Blastocyst formation
Implantation

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5
Q

Fertilization:

A

sperm penetrates a secondary oocyte/mature egg

A zygote is formed when sperm fertilizes an egg

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6
Q

Cleavage:

A

stage characterized by a series of cell divisions

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7
Q

Blastocyst formation:

A

a fluid-filled cavity is formed

organizes the cells into an inner (embryoblast) and outer (trophoblast) cell mass

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8
Q

Implantation:

A

the blastocyst implants into the uterine wall

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9
Q

Pre-Embryonic Period: Week 2

A

During week 2, a bilaminar embryonic disc forms

The embryoblast differentiates into 2 layers:
> Epiblast
> Hypoblast

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10
Q

Epiblast:

A

dorsal row of cells that will develop into the entire embryo and all adult structures

A fluid-filled cavity forms in the epiblast cells, which is called the amniotic cavity

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11
Q

Hypoblast:

A

ventral row of cells that form supporting structures of the embryo

Hypoblast cells migrate down to line the inner surface of the cytotrophoblast cells, and ultimately line a fluid filled space called the yolk sac

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12
Q

The epiblast and hypoblast together form a flat, ovoid shaped disk called the ____

A

bilaminar embryonic disc

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13
Q

Embryonic Period: Week 3 – Gastrulation

A

process that transforms the bilaminar embryonic disc into a trilaminar embryonic disc

cells rapidly divide to replace hypoblast cells and create a middle layer of cells, called mesoblasts

results in the 3 primary germ layers, which will form all adult structures:
> ectoderm
> mesoderm
> endoderm

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14
Q

Surface ectoderm will form:

A

the skin, hair, and nails

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15
Q

neuroectoderm will form the:

A

nervous system

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16
Q

Mesoderm is a major precursor for:

A

muscles and connective tissues of the adult body

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17
Q

Embryonic Period: Week 4 – Neurulation

A

embryonic process that forms the nervous system

occurs during week 4

Ectodermal cells rapidly divide, forming a thickened plate of cells, called the neural plate

The neural plate invaginates down into underlying mesoderm and pinches off, forming the neural tube and neural crest

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18
Q

Neural tube and neural crest (collectively, neuroectoderm) are located in the ___

A

underlying mesoderm

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19
Q

Ectoderm thickens to form the neural plate due to cell division:

A

Ectoderm invaginates because it rapidly divides, causing it to buckle in on itself and invaginate down into the underlying mesoderm

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20
Q

Neurulation begins in the middle of the embryo and extends cranially and caudally =

A

This forms an anterior/cranial neuropore and posterior/caudal neuropore as these are the final regions to complete neurulation and close

By day 28, the neuropores have completed neurulation and are closed

If the neuropores do not close, it may lead to nervous system deficits

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21
Q

Failure of anterior neuropore closure results in ___

A

anencephaly

cerebrum development affected

22
Q

Failure of posterior neuropore closure results in ___

A

spina bifida

tail of spinal cord doesn’t close properly = outpocket into skin

23
Q

Chiari II malformation

A

A condition in which brain tissue extends into the spinal canal, present at birth

It occurs when part of the skull is abnormally small or misshapen

24
Q

Result of neurulation:

A

Neuroectoderm is in the underlying mesoderm and forms the nervous system

Neural tube forms the CNS

Neural crest forms the PNS, connective tissues of the head, and others

Surface ectoderm overlies the neural tube and neural crest and forms surface structures of the body
> Forms epidermis, hair, nails, enamel, and parts of the ears and eyes

25
Q

The neural tube forms:

A

Brain (cerebrum, cerebellum, brainstem)

Spinal cord

Other CNS structures (e.g., pineal gland, part of pituitary gland, retina)

26
Q

The neural tube forms neurons and glial cells of the CNS:

A

Neuroepithelial cells differentiate into neurons or glia

Neuroblasts form neurons

Gliablasts form glia

27
Q

The only glia in the CNS that are not formed from the neural tube are ___

A

microglia

Microglia are formed from the mesodermal germ layer

28
Q

Neural tube:

A

consists of neuroepithelial cells that extend over the entire thickness of the wall and form a thick pseudostratified epithelial layer

Neuroepithelial cells divide rapidly and differentiate into neuroblasts, which form neurons, and gliablasts, which form glial cells

29
Q

The neuroblasts are formed first, followed by ___

A

gliablasts

30
Q

The gliablasts migrate into the mantle and marginal layers of the neural tube to form ___

A

astrocytes

which are located near blood vessels and neurons and provide support and metabolic functions to neurons

31
Q

Gliablasts also form __, which migrate to the marginal layer to form ___

A

oligodendrocytes

the myelin sheath around axons in the CNS

32
Q

Microglia =

A

glial cells that form from the mesodermal layer

not derived from ectoderm

phagocytic cells that develop later than other glia cells and migrate into the CNS

33
Q

Prosencephalon

A

Forebrain (1°)

> (2°) telencephalon forms 2 large lateral outpocketings that develop into the cerebral hemispheres, basal ganglia, and lateral ventricles

> (2°) diencephalon is characterized by the outgrowth of the optic vesicles and forms deeper brain structures, including the thalamus and hypothalamus and the third ventricle

34
Q

Mesencephalon

A

Midbrain (1°)

> mesencephalon (2°) forms the midbrain

> mesencephalon does not change name and forms the midbrain and cerebral aqueduct

35
Q

Rhombencephalon

A

Hindbrain (1°)

> forms the secondary vesicles named the
- metencephalon
- myelencephalon

> The metencephalon (2°) forms the pons and cerebellum and the superior part of the fourth ventricle

> The myelencephalon (2°) forms the medulla and lower part of the fourth ventricle

36
Q

CNS Development: Brain

A

> cranial end of the neural tube forms the brain and brainstem

> rest of the neural tube forms the spinal cord

> at the cranial end, named vesicles form that create the walls and spaces/cavities in the brain and brainstem

> cranial end of the neural tube first forms 3 primary vesicles, called the prosencephalon, mesencephalon, and rhombencephalon (from cranial to caudal)

> the 3 primary vesicles then develop into 5 secondary vesicles

37
Q

CNS Development: Spinal Cord

A

spinal cord develops inferior to the rhombencephalon

marginal layer
mantle layer
neuroepithelial layer

neuroblasts form the mantle and marginal layers of the neural tube

cell bodies of the neuroblasts form the mantle layer and the axons of the neuroblasts form the marginal layer

38
Q

Myelination of the neuroblast axons by ___ makes the appearance of the marginal layer ___, thus, forming the ___

A

oligodendrocytes
white
white matter of the CNS

39
Q

The outer layer of the neural tube is called the ___, which forms the ___

A

marginal layer

white matter of the spinal cord

40
Q

The middle layer of the neural tube is called the ___ and forms the ___

A

mantle layer

gray matter of the spinal cord

41
Q

The inner layer of the neural tube is called the ___ and forms the ependymal cells that line the ____

A

neuroepithelial layer

central canal of the spinal cord

42
Q

The mantle layer differentiates into ____

A

alar plates = dorsal and basal plates, which are ventral

43
Q

The alar plates form the ___, while the basal plates form the ____

A

dorsal gray horn (sensory)

ventral gray horn (somatic motor)

44
Q

The ____ forms in the region between the alar and basal plates

A

lateral/intermediate horn (visceral motor)

45
Q

As a result of continuous addition of neuroblasts to the mantle layer, each side of the neural tube forms thickenings:

a ventral thickening called the ___ and a dorsal thickening called the ____

A

basal plate

alar plate

46
Q

The basal plate contains somatic motor neuron cells that form the ____

The alar plate contains cell bodies of interneurons that form the ____

The lateral (intermediate) horn develops between the ventral and dorsal horns at thoracolumbar spinal levels and contains cell bodies for ____

A

ventral horn of the spinal cord

dorsal horn of the spinal cord

preganglionic sympathetic motor neurons

47
Q

A longitudinal groove, called the ____, serves as the boundary between the alar and basal plates.

The roof plate and floor plate form at the midline of the neural tube, with the roof plate being the ___ and the floor plate being the ____.

A

sulcus limitans

dorsal midline

ventral midline

48
Q

The floor plates are regions that do not contain ___, but instead serve as pathways for nerve fibers crossing from one side of the spinal cord to the other side of the spinal cord.

A

neuroblasts

49
Q

The neural crest forms:

A

Peripheral and cranial nerves and their ganglia

Face and skull bones

Connective tissues in the head

Some other structures in the body as well

50
Q

PNS Development

A

Neural crest cells migrate to form PNS structures, including:
> cranial nerve ganglia
> dorsal root ganglia
> spinal nerves
> sympathetic trunk
> collateral ganglia
> adrenal medulla
> enteric nervous system

Neural crest cells also form Schwann cells which create the myelinate sheath around PNS axons

51
Q

neural crest cells forming the dorsal root ganglia contain the cell bodies of ____ sensory neurons

A

pseudounipolar

The central process of these sensory neurons grows into the dorsal horn to from the dorsal root, while the peripheral process grows toward the periphery

somatic motor neuron axons grow out of the ventral horn to form the ventral root

Neuroscience - spring 2024 (10 decks)

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