Study your flashcards anywhere!

Download the official Cram app for free >

  • Shuffle
    Toggle On
    Toggle Off
  • Alphabetize
    Toggle On
    Toggle Off
  • Front First
    Toggle On
    Toggle Off
  • Both Sides
    Toggle On
    Toggle Off
  • Read
    Toggle On
    Toggle Off
Reading...
Front

How to study your flashcards.

Right/Left arrow keys: Navigate between flashcards.right arrow keyleft arrow key

Up/Down arrow keys: Flip the card between the front and back.down keyup key

H key: Show hint (3rd side).h key

A key: Read text to speech.a key

image

Play button

image

Play button

image

Progress

1/54

Click to flip

54 Cards in this Set

  • Front
  • Back
In what order are the axes of the nervous system set up?
First: Anterior/posterior

Then:
When can you first see regionalization in an embryo?
Even before it is an embryo - regionalization can be set up by maternal transcripts in the egg during meiosis.
What is the very initial thing that induces neurulation?
Cellular movements that occur during gastrulation - creating TISSUE PROXIMITIES.
So when is polarity set up in an embryo?
Prior to fertilization.
What event follows fertilization to prepattern the blastula?
Calcium release activated by the union of sperm and egg.
Poles of the developing embryo:
Animal (dorsal)
Vegetal (ventral)
What 3 layers does the mesoderm underlying ectoderm differentiate into?
-Ventral mesoderm (left)
-Intermediate mesoderm (middle)
-Dorsal mesoderm (right)
Where is the Organizing center for neurulation induction?
In dorsal mesoderm
What does a Comparitive species diagram of gastrulation show?
That although morphologically different, the cell-cell interactions and molecular signals are conserved for gastrulation and NS induction.
How does the dorsal organizer induce neurulation?
It secretes molecules that REPRESS ectoderm formation and as a result NEURAL TISSUE results as a default.
What is the molecule that must be repressed in order for ectoderm to not become ectoderm?
BMP4
BMP is what
Bone morphogenetic protein - if it is not repressed, neural ectoderm will not become that.
What inhibitor molecules are secreted from the Dorsal organizing center?
-Chordin
-Noggin
-Follistatin
-Xnr3
What do the factors secreted by the dorsal organizing center do?
Inhibit BMP4 from allowing ectodermal conversion into epidermis, so that it will by default become neuroectoderm.
What other type of factors are produced by the mesoderm underlying the developing NS?
Regionalization factors
What factor induces Anteriorization?
Antivin - it inhibits Activin
What factor induces Posteriorization?
Retinoic Acid
What happens if Antivin is overexpressed?
No trunk region will develop, only anterior.
What is an important factor in determining regionalization and neuroectodermal conversion?
CONCENTRATION GRADIENTS of the secreted factors.
How do the eyes develop?
From one single field of cells - part of the diencephalon, but able to be distinguished as one field via the use of markers.
What allows for 2 eyes to develop from one region?
Morphogenic movements of Diencephalic precursors that migrate into the retinal field under the influence of Sonic Hedgehog factors.
What would happen to the eyes if there were no Sonic Hedgehog factors?
Cyclopia
WHEN DOES ANTERIOR TO POSTERIOR PATTERNING OCCUR IN THE NEURAL TUBE?
PRIOR TO REGIONALIZATION IN THE DORSAL-VENTRAL DIRECTIONS.
What genes are primarily responsible for A-P patterning?
Hox genes
What are Hox genes?
Highly conserved DNA-binding factors that pattern the hindbrain - they work by regulating whole NETWORKS of differentiation.
What do mutations in the Hox genes result in?
Conversion of whole tissues and organs into mutant types.
What is it called when a Hox gene undergoes mutation?
Homeotic Transformation
How do Hox genes compare between Humans and Drosophilae?
There is synteny - homology not only at the Amino Acid level, but also in how they are arranged on chromosomes.
What is different about how Hox genes function in humans/mammals compared to Drosophilae?
Drosophilae: patterns the entire body plan
Humans: provides molecular addressing to the nervous system
What part of the nervous system development is directed by Hox genes in humans?
From the hindbrain to the spinal cord.
What are the actual structures that are affected by Hox genes to cause AP axis development in the hindbrain and spinal cord?
Rhombomeres
What are Rhombomeres?
Little bumps in the hindbrain; microflexures that develop and will produce the cranial nerves.
How many rhombomeres are there?
7
What makes the rhombomeres different from one another?
The combination of factors that their genes encode; includes Hox genes, Ephrins, Eph-kinases, and other trscrp factors
What is the actual function of Hox genes themselves in rhombomeres?
Gives individual identification to the neurons that will develop in those rhombomeres - e.g. which cranial nerve will develop.
What causes a homeotic mutation?
A mutation in one of the genes for the rhombomeres, making its molecular address look similar to that of another rhombomere.
what TYPE of regulation is illustrated by the COMBINATORIAL CODING of Hox genes?
Autonomous self-regulation
What is a type of Inductive signalling that is important for morphogenesis in the Cerebellum and Midbrain?
The midbrain-hindbrain organizing center - THE ISTHMUS.
What does the Isthmus do?
Secretes FGF8, which induces the expression of Engrailed 2 in a concentration dependent manner.
How does Engrailed2 act?
It induces different morphogenesis cascades based on whether it is in Anterior or Posterior regions of the mid/hindbrain.
What happens to the nervous system after the Anterior/posterior axis is set up?
Dorsal-ventral regionalization
What allows for D/V regionalization in the spinal cord?
Prepatterning by the Alar roof plate and basal floorplate.
What induces ventralization of the spinal cord?
Sonic hedgehog from the NOTOCHORD.
What happens if you don't have sonic hedgehog?
-No ventral nerves (MOTOR)
-Cyclopia
-Prosencephaly
What induces dorsalization of the spinal cord?
Signals from the overlying ectoderm - BMP7
What determines the neurons that will develop in the dorsal to ventral axis in the spinal cord?
The concentration gradients of the factors (BMP7 and Sonic Hedgehog) at each level.
What is the mechanism by which very subtle differences in cells can cause morphological differentiation?
Feedback mechanisms - like lateral inhibition.
What is the mechanism that specifies neuronal subtype differentiation?
Combinatorial Coding - expression of different factors and receptors determines the differentiation that will occur.
3 Types of Neural Tube Disorders:
1. Anencephaly
2. Encephalocele
3. Spina bifida
What is anencephaly?
incomplete devo and subsequent degeneration of forebrain.
What is Encephalocele?
Herniation of neural tissue usually due to incomplete closure of the neural tube.
What are 2 types of Spina bifida?
Meningocele - protrusion of neural tissue thru vertebral column
SB Occulta - incomplete fusion of spine thats asymptomatic.
What prevents NTDs?
Folic acid
Why does folic acid help prevent neural tube defects?
Because it allows metabolism of Homocysteine which is a teratogen.