Development Of The Nervous System

Front 1

What is the Pre-embryonic Period?

Back 1

Zero - 2 weeks

Front 2

What occurs when a zygote develops

Back 2

Series of mytotic divisions --> morula (ball of cells)

Intercellular spaces consolidate to forma cavity and inner cells move to one pole (embryoblast)

Front 3

What is a Blastocyst?

Back 3

Outer epithelial wall and attaches to the uterine wall

Front 4

What occurs during Wk 2 of the Pre-Embry

Back 4

Bilaminar Germ Disc formation

- Uteroplacental circullaion is est

-Inner cell mass differentiates into two layers

Front 5

What are the two layers of the inner cell mass?

Back 5

Epiblast - amniotic cavity develops here

Hypoblasts - exocoelomic cavity

-later produces cells that forms the smaller yolk sac

Front 6

When is the Embryonic period?

Back 6

3-8weeks

Greatest susceptibilty to teratogensis (outside influences)

Front 7

What occurs during week 3?

Back 7

Trilaminar germ disc formation

-Gastration occurs - 3 germ layers est

Front 8

What is the primitive streak?

Back 8

Forms on surface of epiblast

Primitive node forms near P. Streak cephalic end

Front 9

How do Epiblast cells travel in week 3?

Back 9

Invaginate in the primitive pit and travel rostrally to form the definitive notochord

Migrate through the steak to form endoderm and mesodern.

some remain as ectoderm

Front 10

What is the notochord?

Back 10

Serves as basis for the axial skeleton

Front 11

What are the major accomplishments of wk 3-8

Back 11

Periodof organogenesis where ectoderm, mesoderm, and endoderm give rise to specifictissues and organs, establishing major features of body form.

Front 12

Describe the Endoderm?

Back 12

Forms epithelial lining of resp, gasto, and urinary bladder

Forms parenchyma of thyroid gland liver and pancreas

Tympanic cavity and eustachian tube

Front 13

Describe the Mesoderm

Back 13

Tendon, Cartilage, bone, and skin

Forms urogenital structures (intermediate mesoderm)

Lateral Plate - lateral and ventral body wall, wall of gut

Front 14

Describe the ectoderm?

Back 14

Gives rise to structures that maintain contact with the outside world

Epidermis

Sensory epithelium of eye, ear, nose

CNS and PNS

Front 15

When does the Neural tube form?

Back 15

Week 3-4

Front 16

What forms the neural plate?

Back 16

Thickened ectoderm dorsal to the notochord

Front 17

What forms the neural folds and groove?

Back 17

Lateral edges thicken forming folds and with a depressed midregion

Front 18

What is a neural crest cell?

Back 18

Appears along edge of neural folds and give rise to important PNS structures

Front 19

What do neural crest cells differentiate into

Back 19

Dorsal root and cranial nerve sensory ganglia neurons

Post ganglionic and enteric visceromotor neurons

Schwann cells - myelination in PNS

Chromaffin - adrenal medulla

Melanocyte - pigment

Pia and arachnoid mater

Front 20

How is the neural tube formed?

Back 20

When nueral fold fuse in the mid line

proceeds cranially and causdally in a zipper like fashionl

Front 21

When do the neuropores close?

Back 21

Anterior neuropore - 24-26

Posterior Neuropore - 25-28

Front 22

How to help prevent neural tube defects

Back 22

Folic acid during pregnancing

Front 23

Describe Arnold-Chiari Malformation

Back 23

Often occurs at the anterior neuropore

Cerebellar vermis herniates through the formen magnum and compresses the medula and C-Spine

Front 24

Define Spina Bifida

Back 24

Defects involving the closure of the posterior neuropore - myeloschisis

Vertebral arch fails to form completely and fuse

Front 25

What is spina bifida occulta

Back 25

Mildest form - Skin closes over the top

Affects up to 10% of other wise normal individuals - often marked by a patch of hair

Front 26

Describe Spina Bifida Cystica

Back 26

Has accompanying cystic mass

Meningocele - meninges and CSF

Meningomyelocele - meninges, CSF, and spinal cord 5/10kbirths

Front 27

What are the causes of spinal bifida cystica

Back 27

Often are accompanied by hydrocephalus because of associated spinal cord adhesion to the vertebral column and Arnold chiari malformation

Front 28

Primary vs Secondary Neurulation

Back 28

P: Formation down to S2

S: Sacral and Coccygeal

Front 29

What is tethered cord syndrome

Back 29

Form of myelodysplasia - defect of secondary neurulation.

Bottom of SC and Filum Term are abnormallt fixed to the defective vertebral column

Progressive

Front 30

What can tension in the spinal cord result in?

Back 30

Weakness of the lower limb, sensory deficits, pain, and loss of bladder control

Front 31

What are the three primary brain vesicles the neural tube differentiates into

Back 31

Prosencephalon - forebrain

Mesencephalon - midbrain

Rhombencephalon - Hind brain

Front 32

What are neuroepithelial cells?

Back 32

Form pseudostratified epithelium and makes up the wall of the neural tube

Front 33

What occurs during transverse differentiation

Back 33

-Dorsal and ventral thickening of the lateral wall

-Alar and basal plates

-Sulcus Limitans

little is differentiated in midorsal/ventral areas

Front 34

What does the Alar plate give rise to?

Back 34

Sensory Neurons

Cerebellum

Thalamus

Basal Nuclei

Cerebral Cortex

Front 35

What does the Basal Plate give rise to?

Back 35

Motor Neurons

Hypothalamus

Retina

Front 36

What do neuroepithelial cells differentiate into

Back 36

Neuroblasts and gliablasts

Front 37

How do neurons mature?

Back 37

Axonal growth, dendrite development, synaptogenisis

Front 38

What do Glialblasts differentiate into?

Back 38

Astrocytes, oligodendrocytes, and ependymal cells

Front 39

Describe Radial Glia

Back 39

Present during development but ultimately differentiate into astrocytes

Provide scaffold that is critical for guiding migration of immature neurons during the formation of the cerebral cortex

Front 40

What cellular events occur postnatally?

Back 40

Development of the nervous system

-Neuronal density

-Neuronal process branching and myelination

-pattern of synaptic contacts