Lecture 9 Flashcards by Karolina Kowalczyk

the folding process in vertebrate embryos, which includes the transformation of the neural plate into the neural tube; the formation of the nervous system from the ectoderm

neurulation

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In neurulation, the embryo is called the ___.

neurula

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when the anterior part of the neural tube forms a series of bulges called vesicles, which become the primary anatomical regions of the brain: the forebrain (prosencephalon), midbrain (mesencephalon), and hindbrain (rhombencephalon)

regionalization

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What are the 4 regions formed in regionalization?

forebrain, midbrain, hindbrain, spinal column

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the growth and development of nervous tissue

neurogenesis

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What are the steps in neural development?

neurulation, regionalization
neurogenesis
migration
differentiation
axon guidance
synapse formation
cell death
synaptic rearrangement

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What are the 3 primary germ layers during gastrulation?

ectoderm
mesoderm
endoderm

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a phase early in the embryonic development of most animals, during which the single-layered blastula is reorganized into a multilayered structure known as the gastrula

gastrulation

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The ectoderm forms what?

epidermis
CNS
PNS

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The mesoderm forms what?

kidneys
reproductive organs
bones
muscles
vascular system

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The endoderm forms what?

intestines
lungs
liver

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____ cells are pre- programmed to become neurons

ectodermal

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What does dissociation from other cells cause ectodermal cells to do?

differentiate into neurons

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What causes ectodermal cells to differentiate into the skin?

inhibitory signals from other ectodermal cells (remaining intact)

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How does the mesoderm affect ectoderm differentiation?

it blocks the signals from other ectoderm, allowing it to differentiate into neurons

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What is the role of BMP 4?

It induces ectodermal differentiation into skin, even when dissociated

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portion of mesoderm that normally gives rise to the notochord

the organizer

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a cartilaginous skeletal rod supporting the body in all embryonic and some adult chordate animals

notochord

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What does the neural crest form?

PNS

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Where do the ectodermal placodes arise from and what do they form?

non-neuronal ectoderm

- sensory epithelia and cranial nerves

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What does the neural tube form?

brain and spinal cord

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when the neural tube fails to close at the head (fatal)

anencephaly

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when the neural tube fails to close at the tail (correctable)

spina bifida

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a group of related genes that control the body plan of an embryo along the head-tail axis; expressed head to tail

Hox (homeobox domain)

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What determines dorsal-ventral polarity?

the notochord

What happens if we remove the notochord?

no motor neurons form

What happens if we transplant the notochord?

ectopic motor neurons form

The ___ is expressed in the floor plate of the neural tube and the notochord and ___ is expressed in the roof plate of the neural tube and the ectoderm. Both signals contribute to ____.

Shh BMP dorsal-ventral polarity

Shh and BMP ____ to specify the identity of neural progenitors.

antagonize each other

BMP in the epidermal ectoderm leads to the formation of ____

dorsal interneurons

Shh in the notochord (mesoderm) leads to the formation of ____

motor and ventral interneurons

a signaling molecule that acts directly on cells (not through serial induction) to produce specific cellular responses dependent on morphogen concentration. During early development, morphogen gradients generate different cell types in distinct spatial order.

morphogen (french flag model)

Which signaling molecules makes use of the french flag model?

Shh

Differing Shh levels induce different combinations of ____

transcription factors

Shh signaling establishes a spatial organization of ____. | Distinct classes of neurons (motor or interneurons) arise from each ____.

progenitor cells | progenitor domain

when a single cell layer (neural tube) becomes a multi-layered structure (brain/spinal cord)

proliferation

neural precursors with limited self- renewal capabilities

progenitor cells

Progenitors cells give rise to ___ and ___ (more restricted)

radial glia | basal progenitors

How does a cell know what to become?

``` extrinsic influences (cell-to-cell interactions) intrinsic influences (programmed): gene profile based on developmental history ```

Cells of the neural tube give rise to both immature ___ and ___

neurons | glia

Sequential generation of neurons and glia depends on what two things?

- presence of growth factors at specific developmental times - signaling pathways they activate

The neocortex consists of __ layers.

Layers II, III, V, and VI consist of what cells?

glutamergic pyramidal cells

Layer IV consists of what cells?

GABAergic stellate cells

Neuroblasts migrate along ___ and “exit” at the | appropriate location.

radial glia

Cortical layers form ___.

inside out

What molecules induce the formation of the following cells from a neural crest progenitor: sensory neuron, sympathetic progenitor, melanocyte, chromaffin cell progenitor

sensory neuron: leukocyte inducing factor (LIF) sympathetic progenitor: FGF2 melanocyte: stem cell factor chromaffin cell progenitor: glucocorticoids

What molecules induce the formation of the following cells from a sympathetic progenitor: adrenergic neuron, cholinergic neuron

adrenergic neuron: NGF | cholinergic neuron: ciliary neurotrophic factor

What molecule induces the formation of the chromaffin cell from a chromaffin cell progenitor?

glucocorticoid

What are the 3 phases of axon navigation to target?

1. pathway selection: which route to take 2. target selection: which structure to innervate 3. address selection: which cells within target

What guides axonal growth?

physical cues ("functional molding" of random connections)

What did the experiment with a rotated eye and severed axons in a frog show?

frogs couldn't correct; the cells and fibers of the brain and cord must carry some kind of individual identification tags, presumably cytochemical in nature, by which they are distinguished one from another

big actin-supported extension of a developing or regenerating neurite seeking its synaptic target

axon growth cone

How do axon growth cones function?

The highly dynamic nature of growth cones allows them to respond to the surrounding environment by rapidly changing direction and branching in response to various stimuli.

a long, slender, tapering pseudopodium, as found in some protozoans and in embryonic cells

filopodia

a flattened extension of a cell, by which it moves over or adheres to a surface

lamellipodia

What two molecules aid in axon guidance and cytoskeleton formation?

- filopodial protrusion by actin polymerization | - microtubules in axon shaft

Axon migration affected by ___

signals (repulsive, attractive, permissive)

What 3 signals affect axon migration?

diffusible factors - secreted by cells (slit semaphoring, NGF) extracellular matrix molecules (laminin, collagen, fibronectin) cell-cell contact - surface receptors/ligands (CAMs, Cadherins, ephrins)

What extracellular metric molecule do neurons prefer the most? Why?

neurons prefer laminin over collagen (in vivo); laminin binds to integrins on axons

unidirectional movement of a cell, in response to a chemical gradient of ligands; diffusible factors

chemoattraction/chemorepulsion

Cell as the midline of the brain secrete ____. Axons with ___ migrate towards midline (chemoattraction).

``` netrin netrin receptors (DCC) ```

Midline cells also secrete __. Axons that cross the midline upregulate ___. Cells with these receptors are repelled by ___ (chemorepulsion)

slit robo (slit receptor) slit

What is the function of slit and robs receptors?

The prevent cells that cross the midline from re-crossing

Cells with robo receptors stop responding to ___.

netrin

Describe the role of netrin and slit in retina-tectal projections.

- Netrin attracts axons to the optic chiasm | - those that express Slit cross the chiasm.

Chemorepellent responsible for retinal ganglion cell outgrowth onto tectal membrane extracts

ephrins

How does ephrin work?

similar to french flag model... uses a gradient of ephrin receptors on the retina and ephrin ligands on the tectum to match axonal growth

What are the steps in synapse formation?

1. dendritic filopodium contacts an axon 2. contact leads to recruitment of synaptic vesicles in presynaptic cell 3. formation of active zone triggers clustering of postsynaptic receptors

Adhesion molecules (____) are expressed on both pre- and post- synaptic cells to ___.

N-cadherin | stabilize the synapse

What are the steps in synapse formation at the NMJ?

1. growing motor neuron secretes agrin 2. agrin interacts with MuSK receptors on muscle 3. activation of MuSK leads to clustering of ACh receptors via rapsyn 4. basal lamina stimulates Ca2+ entry and NT accumulation 5. both membranes undergo cytoskeletal changes * Synaptic transmission occurs rapidly; final maturation takes weeks

How does a growth cone know which of the 30 muscles to innervate?

splicing for synapse specificity mediates self-avoidence

Lecture 9 Flashcards

(72 cards)