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Molecular Biology - Unit 3 - Zach H. > Development of Multicellular Organisms II: Neural Development > Flashcards

Development of Multicellular Organisms II: Neural Development Flashcards

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1
Q

How many neurons does the brain have?

A

1x10^11 neurons

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2
Q

The brain has 1x10^11 neurons, with each neuron making connections with how many other neurons?

A

about 1000 other neurons

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3
Q

How many phases are there in neural development?

A

3 phases

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4
Q

What happens in phase 1 of neural development?

A

Different cell types (neurons, glia, muscle cells) develop independently at widely separate locations in embryo according to local program and are unconnected.

** genesis of neurons **

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5
Q

What happens in phase 2 of neural development?

A

Axons and dendrites grow out along specific routes setting up a provisional but orderly network of connections between various parts of the system.

** outgrowth of axons and dendrites **

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6
Q

What happens in phase 3 of neural development?

A

continues into adult life, connections are adjusted and refined through interactions with distant regions via electric signals.

** refinement of synaptic connections **

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7
Q

What other cell type in the nervous system are neurons produced in association with?

A

Glial Cells (provide supporting framework and nutrition).

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8
Q

What do are both neurons and glial cells developed (derived) from?

A

Ectoderm - from a common precursor.

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9
Q

What makes up the central nervous system?

A
  • brain
  • spinal cord
  • retina
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10
Q

What structure is the central nervous system derived from?

A

neural tube

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11
Q

What make up the peripheral nervous system?

A
  • nerves

- sensory neurons

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12
Q

What structure is the peripheral nervous system derived from?

A

neural crest

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13
Q

True or False:

The neural tube is derived from a mutli-layered epithelium.

A

False - neural tube is derived from a single layered epithelium.

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14
Q

What does the formation of the neural tube start with?

A

Starts with a neural groove on the dorsal side of the embryo.

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15
Q

What is formed as the neural groove gradually deepens during neural tube formation?

A

Neural folds become elevated as the the neural groove gradually deepens.

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16
Q

What ultimately happens in neural tube formation when the neural folds meet and coalesce in the midline?

A

Ultimately the neural folds meet and coalesce in the middle line and convert the groove into a closed tube, the NEURAL TUBE.

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17
Q

What is the center of the neural tube called?

A

Neural Canal

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18
Q

What signaling mechanisms (and ligand) controls differentiation into neurons in the neural tube?

A

Delta Notch signaling (lateral inhibition).

    • Delta is the ligand **
    • Notch is the receptor **
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19
Q

Signal proteins secreted from ventral and dorsal side of neural tube act as opposing morphogens. What does this cause?

A

Causes neurons at different dorso-ventral positions to express different gene regulatory proteins.

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20
Q

What morphogen is secreted by the roof plate and adjacent cells of the neural tube?

A

BMP proteins

important in production of extracellular matrix and pattern formation

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21
Q

What morphogen is secreted by the floor plate and notocord of the neural tube?

A

Sonci Hedgehog protein

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22
Q

At which end of the neural tube does neural crest cells originate?

A

dorsal end

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23
Q

At what point do neural crest cells migrate extensively to generate several differentiated cell types?

A

Migrate extensively during or shortly after closure of the neural tube or neurulation.

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24
Q

What are the several differentiated cell types that are generated by neural crest cells?

A
  • Neurons and glial cells of the PNS.
  • Epinephrine-producing cells of the adrenal gland.
  • Many of the skeletal and connective tissue components of the head.
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25
Q

What does the fate of neural crest cell differentiation depend on?

A

Where they migrate to and settle.

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26
Q

After final division close to the inner face of the neural tube, how do neurons migrate?

A

Crawl along radial glial cells.

  • radial glial cells extend from inner to outer end of the neural tube *
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27
Q

In the development of the spinal cord, what modulates the characteristics of neurons and the connections they make?

A

Differences in Gene Expression

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28
Q

What neurons of the spinal cord receive and relay sensory information from sensory neurons located in the periphery of the body?

A

Dorsal Neurons

29
Q

What do ventral clusters of spinal cord neurons develop as?

A

Motor neurons - send out long axons to connect with specific subset of muscles.

30
Q

What type of neurons are found in the intermediate location within the spinal cord?

A

Inter-neurons - that connect specific set of nerve cells to each other.

31
Q

What is the composition of a typical immature neuron?

A
  • cell body
  • long axon
  • several short dendrites
32
Q

What is a “growth cone”?

A

Tip of axon/dendrite has an irregular, spiky enlargement - called growth cone.

33
Q

What is the tip of an axon/dendrite that has an irregular, spiky enlargement called?

A

Growth Cone

growth cone crawls through surrounding tissue, trailing the axon or dendrite behind

34
Q

True or False:

The growth cone at the tip of a axon/dendrite crawls through surrounding tissue, trailing the axon or dendrite behind and has the engine and steering apparatus that directs the process along the right path.

A

True

35
Q

What is formed once the growth cone starts migrating fast and develops axon-specific proteins?

A

Axon is formed.

36
Q

What machinery dictates growth cone behavior?

A

Cytoskeletal machinery

they through out filopodia and lamelopodia

37
Q

What controls the assembly/disassembly of actin filaments, which control movement of growth cone?

A

Monomeric GTPases Rho and Rac.

38
Q

What phase of neural development are we in during migration of the growth cones?

A

Phase 2

39
Q

In the migration of growth cones, what two major cues are are used to find their way?

A
  • Extracellular matrix environment sensed by receptors present on membrane.
  • Chemotactic factors released by neighboring cells.
40
Q

What is contact guidance?

A

The growth cones often follow a path taken by other cells.

** consequently, nerve fibers are usually found in bundles **

41
Q

What is contact guidance mediated by?

A

homophilic cell adhesion molecules

42
Q

What are the two important classes of homophilic cell adhesion molecules that mediate contact guidance in the migration of growth cones?

A
  • Immunoglobulin superfamily

- Cadherin family

43
Q

What do homophilic cell adhesion molecules provide a mechanism for?

A

Selective guidance and recognition - for migration of growth cones (contact guidance).

44
Q

What matrix molecule favors axonal outgrowth?

A

laminin

45
Q

What matrix molecule inhibits growth?

A

chondroitin sulfate proteoglycans

46
Q

What are the two signals in which chemotactic factors can send?

A
  • attractive
  • repulsive

Examples:
> Netrin - attractant
> Slit - repellent
> Semaphorin - repellent

47
Q

What does the first stage of the commissural neuron guidance mechanism depend on?

A

Secretion of NETRIN by cells of the floor plate.

48
Q

In the mechanism of commissural neuron guidance, what cells secrete netrin (attractant)?

A

Cells of the floor plate.

49
Q

What does the binding of netrin to its receptor cause?

A

Opening of TRPC (transient receptor potential C) channels.

this allow entry of calcium

50
Q

Nectin binding to its receptor causes the opening of TRPC channels, which allow entry of extracellular calcium. What does this influx of calcium activate?

A

Activation of machinery for extension of filopodia and movement of the growth cone.

51
Q

True or False:

Non-commissural neurons in the neural tube also have netrin receptors, thus, allowing them to migrate towards the floor plate.

A

False - Non-commissural neurons in the neural tube do NOT have netrin receptors, so they do NOT migrate towards the floor plate.

52
Q

In the mechanism of commissural neuron guidance, what chemotactic molecule is secreted by midline cells?

A

Slit (repellent)

  • slit repels growth cones and blocks entry to the midline *
53
Q

What is the function of the chemotactic molecule slit?

A

Repels growth cones and blocks entry to the midline.

54
Q

Growth cones become sensitive to another repulsive signal called semaphorin. What does this cause the growth cones to do?

A

They become trapped between 2 sets of repellants (slit and semaphorin), which causes the growth cones to travel in a narrow track.

55
Q

What regulates which growth cones synapse and where?

A

signal from target tissue

56
Q

True or False:

Unidirectional signaling in nerve cells but in developing cells are bidirectional.

A

True

57
Q

True or False:

Most neurons are made in excess and up to 50% die after they reach the target cell.

A

True

58
Q

True or False:

Target cell produces limited amount of specific neurotrophic factors needed for survival.

A

True

those that do not get enough die by programmed cell death

Can be reversed by increasing number of target cells and exacerbated by decreasing number of target cells

59
Q

What was the first prototypical neurotrophic factor to be identified?

A

Nerve Growth Factor (NGF)

60
Q

What family does nerve growth factor (NGF) belong to?

A

Neurotrophins

61
Q

What type of a receptor is the NGF receptor?

A

tyrosine kinase (TrkA)

62
Q

What does nerve growth factor (NGF) promote?

A

Survival of specific sensory neurons and sympathetic neurons.

63
Q

What are the short term effects of NGF?

A

Effect on growth cone and neurite extension.

Effect is local, direct rapid, and independent of communication with cell body.

64
Q

What are the long term effects of NGF?

A

Effect on cell survival.

Mediated by its receptor, uptake into cells via endocytosis and stimulation of downstream signaling pathways.

65
Q

What are the 2 rules that synaptic remodeling is dependent on for creating spatial order?

A

(1) Axons from cells in different regions of retina (which are excited at different times) compete for tectal neurons.
(2) Axons from neighboring sites which are excited at same time cooperate/collaborate to retain and strengthen synapses with tectal neurons.

66
Q

What does activity-dependent synaptic remodeling depend on?

A

Electrical activity and synaptic signaling.

Neurons that fire together wire together.

67
Q

What action strengthens synapses?

A

External events that cause 2 or more neurons to be activated at the same time.

68
Q

What effect does calcium have on synaptic strength?

A

Entry of Calcium through the glutamate receptor (NMDA receptor) triggers lasting change in synaptic strength.

> This causes corresponding change in physical structure of synapse.

> Individual dendritic spines remodeled, new spines appear with electrical stimulation.

Molecular Biology - Unit 3 - Zach H. (9 decks)

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