Formation Of The Nervous System - 31 Flashcards
What is Gastrulation?
The invagination to form the three germ layers
What positions are determined during gastrulation?
Midline, anterior-posterior, dorsal-ventral
What is the “animal hemisphere” in amphibians?
The part of the egg that is you’ll free
What is the area called where the yolk is in amphibians?
The Vegetal Hemisphere
Where does the invagination take place in amphibians? Humans?
Blastopore : Primitive Streak
Why do humans not need an animal and vegetal hemisphere?
Our embryos get their nutrients from the placenta.
What structure is formed during gastrulation? What germ layer forms it?
The Notocord : mesoderm
What structure defines the midline of an embryo?
The Notochord
What process occurs after gastrulation?
Neurulation
What is neurulation?
The notochord sends inductive signals to the overlying ectoderm inducing neuroectoderm cells. Which will give rise to the entire nervous system.
What is the neural plate?
A thickening of the midline ectoderm into columnar epithelium.
What structures does the neural tube give rise to?
The brain and spinal cord
Neural stem cells of the _________________ are called ____________________. The give rise to precursors that can make ________________, _________________, __________________.
Neural tube : Neural precursor cells : neurons, astrocytes, and oligodendrocytes.
This precursor has stopped dividing and will differentiate into neurons
Neuroblasts
This part of the neural tube is most differentiated.
The Floorplate
What does the floorplate do?
Induces differentiation of the neural precursor cells. Also, gives the neural tube dorsovental polarity.
What are somites and what will they become?
Thickening of the mesoderm adjacent to the neural tube. Will become axial musculature and skeleton.
The brain arises from the _________________.
Anterior neural folds
The peripheral nervous system is formed by the __________________.
Neural crest cells
What are 3 basic principles of inductive cues?
They regulate gene expression (divide, differentiate, migrate); They can be graded (by molecule or receptor); they can be local (cell surface or not diffused)
Where is Shh expressed during neurulation?
The notochord and floorplate
Where is Noggin expressed during neurulation?
The notochord, floorplate, and roofplate (highest in roofplate)
How do cels of the neural tube determine their differentiation?
Gradients of inductive factors (Shh and Noggin)
What do cells of the ventral neural plate differentiate into?
These cells (floorplate) are exposed to more Shh and will become primary motor neurons
What will the cells of the dorsal neural plate become?
These cells are exposed to a high amount of Noggin and will become sensory neurons
Cells exposed to high amounts of Shh will become ___________________, whereas cells that are exposed to high amounts of noggin will become ___________________.
Motor neurons : sensory neurons
What is the organization of the developing brain from Caudal to Rostral?
Cervical flexure : rhombencephalon : cephalic flexure : mesencephalon : Prosencephalon
The prosencephalon will partition into the ________________ (rostral) and the _________________ (caudal)
Telencephalon : diencephalon
The mesencephalon remains. The Rhombencephalon will partition into the _________________ (rostral) and the __________________ (caudal) separated by the _________________.
Metencephalon : myelencephalon : pontine flexure
What are the optic cups?
Outcropping on the diencephelon
The telencephalon gives rise to:
The cerebral cortex, hippocampus, basal ganglia, basal forbrain nuclei, and olfactory bulb
The diencephalon will give rise to:
The thalamus and hypothalamus
The optic vesicles give rise to the:
Retina
The mesencephalon gives rise to:
The superior and inferior colliculi and the midbrain tegmentum
How many days into development are all the brain structures partitioned?
100 days
How much of the fetal development is devoted to cerebral cortex development?
6 months
Neuromeres:
Repeating neural tube units. Cause segmentation of the developing nervous system.
Homeotic genes
(Hox genes) TFs that bind to DNA region known as the homeobox.
Hox genes are expressed in an _______________ to _______________ fashion.
Anterior to posterior
How many times were the human Hox genes duplicated from the ancestral Hox cluster?
Twice
How many neurons/min are generated at the peak of neuro genesis?
250,000
What are the 2 zones of the neural tube from lumen to pial surface?
Close to the Lumen is the VENTRICULAR ZONE; close to the pial surface is the MARGINAL ZONE
Where is the nuclei of neural precursor cells located during each part of its life cycle?
G1- ventricular zone : S- Marginal zone : G2- ventricular : M- detaches from pial surface and divides
What two options does a newly decided cell have during proliferation in the neural tube?
After reconnecting to the pial surface, they can continue to proliferate, or they can stop differentiation and become a neuroblast that differentiates into a neuron
