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Mol Bio Exam III > Neural Development > Flashcards

Neural Development Flashcards

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1
Q

How many connections do neurons make with other neurons?

A

About 1000

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2
Q

Phase 1 of neural development

A

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

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3
Q

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.

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4
Q

Phase 3 of neural development

A

Continues into adult life, connections are adjusted and regained through interactions with distant regions via electric signals

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5
Q

What provides the supporting framework and nutrition to nuerons being produced?

A

Glial cells

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6
Q

What does neurons and glial cells develop from?

A

Ectoderm

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7
Q

CNS (brain, spinal cord and retina) is derived from?

A

Neural tube

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8
Q

PNS (nerves, sensory neurons) is derived from?

A

Neural crest

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9
Q

Formation of the neural tube

A

Derived from a single layered epithelium. Starts w/ neural groove on the dorsal side of the embryo that gradually deepens as nueral folds become elevated. Ultimately the folds meet and coalesce in the middle line and convert the groove into a closed tube (neural tube). Center of the tube is called the neural canal

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10
Q

What controls differentiation into neurons?

A

Delta Notch signaling (lateral inhibition)

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11
Q

Mechanism of delta notch in differentiation of neurons

A

Signal proteins secreted from ventral and dorsal side of NT act as opposing morphogens, causing neurons at different dorso-ventral positions to express different gene regulatory proteins

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12
Q

What is secreted from the roof plate of the neural tube?

A

BMP

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13
Q

What is secreted by the floor plate of the NT?

A

Shh (notochord secretes it too)

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14
Q

Where do neural crest cells originate?

A

Dorsal end of the neural tube

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15
Q

Closure of the neural tube =

A

Neurulation

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16
Q

Neural crest differentiation several differentiated cell types like:

A

Neurons and glial cells of the PNS; epinephrine-producing cells of the adrenal gland; many of the skeletal and CT components of the head

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17
Q

What does fate of the neural crest cells depend on?

A

Where they migrate to and settle

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18
Q

Describe the migration of neurons

A

Neurons migrate from their original birthplace and settle in a different location. After final division close to the inner face of the NT they crawl along radial glial cells which extend from inner to outer end of the NT

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19
Q

Dorsal neurons of spinal cord receive and relay sensory info from ______ neurons located _______?

A

Sensory neurons located in the periphery of the body

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20
Q

Ventral clusters of spinal cord neurons develop as __________ neurons

A

Motor neurons - send out long axons to connect w/ specific subset of muscles

21
Q

Intermediate location has what?

A

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

22
Q

Tip of axon/dendrite has an irregular, spiky enlargement called?

A

Growth cone - crawls through surrounding tissue, trailing the axon/dendrite behind. It has the engine and steering apparatus that directs the process along the right path.

23
Q

One growth cone will start migrating fast and develop what?

A

Axon-specific proteins - will for the axon

24
Q

Growth cone behavior is dictated by what?

A

It’s cytoskeletal machinery b/c they put out filopodia and lemelopodia

25
Q

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

A

Monomeric GTPases Rho and Rac

26
Q

What two major cues are exploited for growth cones to find their way?

A
  1. Extracellular matrix environment sensed by receptors present on membrane.
  2. Chemotactic factors released by neighboring cells.
27
Q

Explain the meaning of contact guidance

A

Growth cones often follow a path taken by other cells (ex - nerve fibers are usually found in bundles)

28
Q

Contact guidance in growth cones is mediated by?

A

Homophilic cell adhesion molecules

29
Q

What are 2 important classes of homophilic cell adhesion molecules that mediate contact guidance in growth cones?

A
  1. Ig superfamily 2. Cadherin family
30
Q

What matrix molecules favors axonal outgrowth?

A

Laminin

31
Q

What matrix molecules INHIBIT growth?

A

Chondroitin sulfate proteoglycans

32
Q

The first stage of commissural neuron guidance depends on secretion of what ligand?

A

Netrin - by cells of the floor plate

33
Q

What is the outcome of netrin binding it’s recepto?

A

Opening of TRPC (transient receptor potential C) channels which allow entry of extracellular Ca, activating machinery for extension of filopodia and growth cone movement.

34
Q

What don’t other cells migrate toward floor plate?

A

They don’t have netrin receptors like commissural neurons

35
Q

What do midline cells secrete?

A

Slit

36
Q

What is the receptor for slit and where is it found?

A

Roundabout. Present on commissural neurons

37
Q

Function of slit

A

Repels growth cones and blocks entry to the midline.

38
Q

What is the second repellant signal along with slit?

A

Semaphorin

39
Q

What regulates which growth cones synapse and where?

A

Signal from the target tissue

40
Q

What are the signals produced by the target cell called and what is their function?

A

Neurotrophic factors; needed for survival (if they don’t get enough they die by programmed death)

41
Q

What was the first prototypical neurotrophic factor to be identified?

A

Nerve growth factor (NGF)

42
Q

NFG Nerve Growth Factor

A

Belongs to the family of neurotrophins. Is a tyrosine kinase (TrkA). Promotes survival of specific sensory neurons and sympathetic neurons

43
Q

Short term effects of NGF

A

Effect on growth cone and neurite extension. Effect is local, direct, rapid and independent of communication w/ cell body

44
Q

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

45
Q

Synaptic remodeling is dependent upon what 2 rules that create spatial order?

A
  1. Axons from cells in different regions of retina (which are excited at differnt times) compete for tectal neurons.
  2. Axons from neighboring site which are excited at same time cooperate/collaborate to retain and strengthen synapses w/ tectal neurons
46
Q

Activity dependent synaptic remodeling depends on what?

A

Electrical activity and synaptic signaling

47
Q

Adult memory

A

Synapses are strengthened by external events that cause 2 or more neurons to be activated at the same time Entry of Ca through the glut receptor NMDA triggers lasting change in synaptic strength. Corresponding change in physical structure of synapse

48
Q

How many neurons does the brain have?

A

10^11

Mol Bio Exam III (5 decks)

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