Nervous System Development I

Question 1

What are the stages of the neural tube wall from that of a simple cuboidal epithelium to a stratified epithelium?

Answer 1

Early neural epithelium- simple cuboidal

Neural Plate- simple columnar epithelium

Early neural tube wall- pseudostratified

Late neural tube wall- stratified epithelium

Question 2

What is the importance of the orientation of the metaphase plate during proliferation of cells within the neural tube?

Answer 2

If the metaphase plate is perpendicular to the inner margin of the neural tube, the two resulting daughter cells will remain proliferative

If the metaphase plate is parallel to the inner margin, the daughter cells closest to the lumen will remain proliferative and those further from the lumen will become postmitotic and become a neuroblast (pre-neuron)

Question 3

What is the influence of the graft secondary notochord near the neural tube to the development of the spinal cord?

Answer 3

Causes another floor plate to be induced

Question 4

What is the influence of removing the notochord to the development of the spinal cord?

Answer 4

Causes ectopic bundles of nerve fibers to form

Question 5

What is the influence of the slit neural plate on one side of the floor plate in regards to the development of the spinal cord?

Answer 5

Causes ectopic bundles of nerve fibers to form on one side and a normal spinal nerve to form on the other side

Question 6

What is the role of Shh in the developing neural tube in regards to the ventral signaling?

Answer 6

Shh induces the formation of the floor plate and motor neurons. Take note that it does not induce sensory neurons

Question 7

What is the relationship between cranial nerves and pharyngeal arches?

Answer 7

Cranial nerves are associated with the caudal end of the brain

Most structures supplied by the cranial nerves are derived from the pharyngeal arches

Question 8

How is the segmented nature of spinal nerves related to the somatic mesoderm pattern?

Answer 8

The segmented nature of the spinal nerves is due to the pattern of somitic mesoderm along the neural tube
-This is because motor neurons can penetrate anterior mesoderm of somites but not posterior mesoderm of somites

Question 9

What is the role of the isthmic organizer, and what signaling/transcription factors are involved?

Answer 9

Isthmic organizer is located between the mesencephalon and the metencephalon and is the signaling center:

• Principle signaling molecule is FGF-8
• Organizes and polarizes the dorsal midbrain and cerebellum

Question 10

How does Shh determine the midbrain dorsoventral axis?

Answer 10

Shh restricts the expression of Pax-7

Question 11

What 2 roles do prosomeres P1-P3 play in forebrain patterning?

Answer 11

P1-P3 define the diencephalon

P2-P3 define the dorsal and the central thalamus

Question 12

What are the steps in the outgrowth of a motor neuron?

Answer 12

Axons grow out from the motor neuroblasts located in the basal plate of the spinal cord

Boundary caps created by neural crest cells maintain separation between the central nervous system components and peripheral nervous system components

Question 13

What are the steps in the outgrowth of a sensory neuron?

Answer 13

Cell bodies of sensory neurons are derived from neural crest cells and form sensory spinal ganglia

Axons grow out from these cell bodies both towards the spinal cord and the periphery

Boundary caps maintain the separation here as well

Question 14

What are growth cones?

Answer 14

Characterized by expanded region of cytoplasm with filopodia

Growth cones advance via extension/resorption cycles that involve actin microfilaments

Question 15

How do environmental factors affect growth?

Answer 15

Chemoattraction
Contact attraction
Chemorepulsion
Contact repulsion

Question 16

What role do netrins and semaphorins play?

Answer 16

Netrins- attractants

Semaphorins- repulsive

Question 17

List cues involved in axon guidance.

Answer 17

Caudal half of somite
Fibronectin and laminin
Integrins
Cadherins

Question 18

What are the steps in the origin of sympathetic preganglionic neurons?

Answer 18

Arise from intermediate (lateral) horns of gray matter- levels T1-L2

Myelinated axons move through the ventral roots of the spinal cord and then through the white communicating rami

Axons enter sympathetic chain ganglia or collateral ganglia

Preganglionic axons synapse with cell bodies of postsynaptic sympathetic motor neurons within the ganglia

From there, they can ascend or descend within the sympathetic chain to more anterior (cranial) or more posterior (caudal) ganglia and synapse with postganglionic neurons.

Question 19

What is the level of origin for the parasympathetic preganglionic motor neurons?

Answer 19

Midbrain, hindbrain, and S2-S4

Question 20

What factors determine whether migrating neural crest cells differentiate into autonomic neurons or other neural crest derivatives?

Answer 20

BMPs determine whether migrating neural crest cells differentiate into neurons or other neural crest derivatives.

Question 21

What are the 5 regions of the Pentapartite brain?

Answer 21

Telencephalon
Diencephalon
Mesencephalon
Metencephalon
Myelencephlon

Question 22

Which structures develop from the Telencephalon?

Answer 22

Paleocortex
Corpus Striatum
Neocortex

Question 23

Which structures develop from the Diencephalon?

Answer 23

Thalamus
Hypothalamus
Epithalamus

Question 24

Which structures develop from the Mesencephalon?

Answer 24

Tectum
Tegmentum
Cerebral Peduncles

Question 25

Which structures develop from the Metencephalon?

Answer 25

Cerebellum

Pons

Question 26

What is the relationship between Shh and Holoprosencephaly? What is Holoprosencephaly?

Answer 26

Mutations in the Shh gene cause holoprosencephaly. This condition occurs when the brain fails to divide into two hemispheres during early development.