Lecture 3: Neurodevelopment Flashcards
____: the process by which the inner cell mass is converted into a trilaminar embryonic disc (end of first week)
Gastrulation
What are the three primitive cell layers?
Endo, ecto, and mesoderm
What is the central event of gastrulation?
Formation of notochord
____: a distinct cylinder of mesodermal cells that condenses at the midline of MESODERM and extends from the mid-anterior to posterior aspect of the embryo
Notochord
The notochord is generated by a surface indentation called the ___ pit, which subsequently elongates to form ____ streak
primitive pit; primitive streak
Which of the following structures comes to define the embryonic midline and, therefore, the axis of symmetry of the entire body?
A. Notochord
B. Neuroectoderm
C. Gastrulation
D. Mesoerm
A. Notochord
____: the ectoderm that lies immediately above the notochord
Neuroectoderm
True or False: Early in vertebrate embryogenesis, the neuroectoderm will give rise to the entire nervous system
True
The notochord (and the primitive pit) send inductive signals to the overlying ectoderm. What is the result of this?
Neuroectodermal cells differentiate into neural precursor cells (NPC’s)
How is the neural plate formed?
Midline ectoderm contains NPC’s, which thicken into columnar epithelium (neural plate)
On what day of development does the neural plate invaginate along its central axis to form the NEURAL GROOVE?
A. Day 9
B. Day 18
C. Day 21
B. Day 18
The neural plate becomes the ___ ___ by week ___
neural tube; week 3
- this happens when the neural folds of the neural plate approach each other and fuse at midline
Which two conditions can arise of the lips of the neural tube fail to fuse?
1) Spinda bifida (caudal spinal cord)
2) Anencephaly (failure of forebrain development)
The walls of the neural tube become thickened to form the ___ and ____
brain and spinal cord
The lumen of the neural tube is converted into which two structures?
Lumen of the neural tube:
1) Ventricular system (brain)
2) Central canal (spinal cord)
Proliferation and differentiation of neuroepithelial cells in the developing spinal cord produces: floor plates, thick __ and thin ___
thick walls
thin roof
True or False: The Posterior Neural Fold will give rise to the brain
False - the Anterior Neural Fold will give rise to the brain
Differential thickening of the lateral walls of the spinal cord will produce a shallow, longitudinal groove known as the _______
sulcus limitans
_____: a shallow, longitudinal groove that separates the alar plate (dorsal) from the basal plate (ventral)
Sulcus Limitans
True or False: The Altar and Basal Plates produce longitudinal bulges, which extend through most of the length of the developing spinal cord
True
True or False: Alar Plates are associates with afferent functions while Basal Plates are associated with efferent functions
True
Which structures in the alar plates form the dorsal gray matter?
Cell bodies
What are the five steps of neurulation?
1) Elongation
2) Folding
3) Elevation of neural folds
4) Convergence
5) Closure
True or False: The Alar Plate is associated with Dorsal Gray Matter (dorsal horn) while the Basal Plate is associated with the Ventral Gray Matter (ventral horn)
True
Alar Plate = Dorsal Gray Matter
Basal Plate = Ventral Gray Matter
Where are the pseudounipolar neurons in the spinal ganglia derived from?
NCC’s
True or False: Since pseudounipolar neurons in spinal ganglia form swellings on dorsal roots of spinal nerves, they are often called DRG (dorsal root ganglia)
True
What two events must occur for the formation of the three primary brain vesicles to develop?
1) Fusion of the neural folds in the cranial region
2) Closure of the rostral neuropore
True or False: The three primary brain vesicles form in the 5th week of development
False - 4th week!
Proencephalon = ____
Mesencephalon = _____
Rhombencephalon = ____
Proencephalon - Forebrain
Mesencephalon - Midbrain
Rhombencephalon - Hindbrain
True or False: A cervical flexure is located in both the midbrain and the hindbrain
False - cephalic flexure in the mesencephalon; cervical flexure in rhombencephalon
By week 6 in development, how many secondary brain vesicles are there?
Six
Forebrain (prosencephalon)
1) Telencephalon
2) Diencephalon
Midbrain (mesencephalon)
Hindbrain (rhombencephalon)
1) Myelencephalon
2) Metencephalon
True or False: During the 5th week of development, the forebrain partly divides into two vesicles: telencephalon and diencephalon
True
Which three adult brain structures arise from the diencephalon?
1) Thalamus
2) Hypothalamus
3) Globus Pallidus
Which three adult brain structures arise from the telencephalon?
1) White matter of hemisphere
2) Cerebral cortex
3) Caudate/Putamen
The metencephalon gives rise to the ___ while the myelencephalon gives rise to the ___ and ___
metencephalon - pons/cerebellum
myelencephalon - medulla
What three conditions must be met to create a precise neural circuit during development?
1) Correct number and type of neurons must be made
2) Assume appropriate position
3) Make proper connections via: synapses
___ the mitotic division of non-neuronal cells to make neurons
A. Cell differentiation
B. Cell migration
C. Neurogenesis
C. Neurogenesis
Where does neurogenesis briefly take place?
Inner layer of the neural tube
____: closely packed layer of cells within the inner layer of the neural tube
The ventricular zone
Once cells leave the ventricular zone, they become either a: ____ or ____ cell
neuron; glial cell
True or False: Once cells begin differentiating, the begin to express a particular set of genes
True
Which three factors affect the particular fate of a differentiating cell?
1) Where in the brain the cell is - regional differences
2) When in development - critical period for cell commitment
3) What neighbor cells are doing - formation of nuclei, clusters
True or False: Cell differentiation based on cell-cell interactions (e.g what neighbors are doing) is a hallmark of vertebrate development
True
What does the caudal portion of the neural rube form?
Spinal cord
Which genes are broadly conserved among animals and play a key role in assigning regional identities along the AP axis?
A. Hox
B. ems
C. otx
A. Hox
Which two genes are transcription factors that play a major role in forebrain development?
otx and ems
True or False: The expression of the emx gene is restricted to the midbrain region and stops abruptly at its boundary within the midbrain
False - the expression of the emx gene is restricted to the FOREBRAIN region and stops at its boundary in the midbrain
True or False: A mutation in emx gene gives rise to gross defects in cortex structure, while otx defect give rise to epilepsy
True
In which stage of development do the cells of the neural tube divide to provide progeny cells?
Neurogenesis
True or False: Cell identity depends on both genes and the environment
True
Note: environment is defined by regional expression of specific genes
Where is ems primarily expressed? otx?
ems - midbrain
otd - forebrain
The segmental pattern of
___ genes plays a key role in
the development of the
hindbrain structures
Hox
____: specialized glial cells located along the ventral midline of the developing neural tube
A. Roof Plate
B. Floor Plate
C. Dinner Plate
B. Floor plate
True or False: The basal region of the neural tube gives rise to motor neurons
True
The more dorsal-alar regions give rise to ____ and that region that is most dorsal forms the ___ and ___
interneurons; roof place; neural crest
What cell types are Sonic Hedgehog initially produced and secreted by?
Cells of the notochord (just ventral to the neural tube)
The specialization in ventral territory depend in large part of a signaling protein known as ____
SHH (sonic hedgehog)
Cells at the ___ portion of the neural tube experience HIGHER levels of Shh and, therefore, are induced to become floor plate cells
A. posterior
B. ventral
B. ventral
True or False: A ventro-dorsal gradient of Shh is est. in the neuronal tube, with the highest concentration in the ventral regions
True
The roof plate generates dorsoventral gradients of which two proteins?
BMP and Wnt proteins
- leads to differentiation of dorsal (sensory) regions of developing spinal cord
True or False: ShH induces production of motor neurons (spinal cord); sertoergic and dopaminergic neurons (hindbrain); oculomotor (midbrain)
True
Cells in the basal region of the neural tube give rise to which type of neurons?
A. Sensory
B. Motor
B. Motor
Sonic Hedgehog induces production of ___ neurons in the spinal cord
motor
____: when neurons extend their axons and dendrites and form many synapses with one another
Synaptogenesis
___ is a sculpting process
Cell death/apoptosis
Neurons compete for connections for structures (synaptic sites) and target-derived chemicals known as _____
neutrotrophic factors
What happens to neurons that do not receive enough neutrophic factors?
They die
___: The loss of some synapses and development of others, to refine synaptic connections
Synapse Rearrangement
An explosion of synapse formation is followed by ____ ___
Synapse Rearrangement (synaptic remodeling)
True or False: The decision about which synaptic connections are retained and which new connections are formed is thought to result from competition for NEUROTROPHIC FACTORS throughout development
True
True or False: As one ages, there is loss of synapses and thinning of cortical gray matter (caudal-rostral direction)
True
True or False: More active synapses compete more successfully than inactive synapses; inactive synapses are lost via: prunning
True
NGF is an example of a ____
neutrotrophin
