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PSYCH 3410 > Lecture 2 - Prenatal Development > Flashcards

Lecture 2 - Prenatal Development Flashcards

1
Q

What does Axon Growth and Synapse Formation begin with?

A

The axon growth cone

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2
Q

What happens at the tip of a growing axon?

A

It extends and retracts filopodia (finger like processes)

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3
Q

What are the two ways growth cones find their way to the target?

A
  1. Chemoaffinity Hypothesis
  2. Topographic Gradient Hypothesis
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4
Q

What is Chemoaffinity Hypothesis?

A

Target-specific chemical labels –> axons grow into the chemical gradient

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5
Q

What is this hypothesis supported by?

A
  • In vitro studies (no spatial cues, only chemical)
  • Discovery of Several chemicals labels that attract or repel neurons
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6
Q

What studies are the Chemoaffinity Hypothesis not supported by?

A
  1. Targets transplanted in new positions can become incorrectly innervated.
  2. The route to the target is often circuitous, rather than linear
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7
Q

What is the Revised Chemoaffinity Hypothesis?

A
  1. Pioneer Growth Cones follow CAMs and other guidance molecules (chemical trails)
  2. Subsequent growth cones follow the pioneer growth cones via fasciculation
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8
Q

What is Fasciculation?

A

The tendency of growing axons to follow previous axons

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9
Q

What is CAMs?

A

Cell Adhesion Molecules

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10
Q

What is a Topographic Gradient Hypothesis?

A

Two intersecting gradients (up-down and left-right) of chemicals on the originating tissue guide axonal growth from one topographic array (such as a retina) to another (the optic tectum)

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11
Q

What is the Topographic Gradient Hypothesis supported by?

A

Maintenance of topographic integrity

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12
Q

What is a Synapse formation called?

A

Synaptogenesis

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13
Q

What does synaptogenesis require?

A

Requires neuron-neuron “talk”

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14
Q

What do Glial Cells (Astrocytes) key for?

A

Synaptogensis

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15
Q

How is synapse formation studied In vitro?

A

Neurons cultured with astrocytes form 7 times as many synapses as those without astrocytes.

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16
Q

How is synapse formation studied In vivo?

A

Stydies with KO mice similarly demonstrate the importance for synapse-promoting and inhibiting signals secreted by astrocytes

17
Q

What happen to neurons during proliferation?

A

There is an overproduction of neurons - about 50% more than actually needed

18
Q

What neurons die?

A

The Neurons that make incorrect connections - as not all neurons are essential

19
Q

What do New Neurons make?

A

More focused synapses

20
Q

What does cell death increase?

A

The overall accuracy of synaptic connections

21
Q

What is Apoptosis?

A

Genetically programmed (good) cell death that is clean and organized

22
Q

What is Necrosis?

A

Bad, passive cell death that is mixed up

23
Q

What causes neurons to die?

A
  1. Genetically programmed (some neurons)

2.) Competition for target supplied neurotrophins

24
Q

What is the first neurotrophic to be isolated?

A

Nerve Growth Factor

25
Q

What are a few Neurotrophins?

A
  • Nerve Growth Factor
  • Brain Derived Neurotrophic Factor
  • Glial Cell-Line Derived Neurotrophic Factor
26
Q

What are Five Functions of Neurotrophins?

A

1.) They promote neuronal growth

2.) They promote neuronal survival

3.) They can function as axon guidance molecules

4.) They can stimulate synaptogensis

5.) Their absence can trigger apoptosis

27
Q

What are methods for Studying CNS development?

A

1.) Non Human Animals (zebrafish, frog, chicks)

2.) Humans
- Prenatal
- Postnatal

28
Q

What happens to the brain after birth?

A

It doubles in volume

29
Q

When is the CNS fully mature?

A

Late Adolescence

30
Q

What is the last region of the CNS to develop?

A

Prefrontal Cortex

31
Q

What happens during Dendritic Branching?

A
  • Parallels pattern of Migration
  • Deeper layers migrate first and are first to sprout dendrites
32
Q

What happens during Synaptogensis?

A
  • Peaks after birth in most brain areas
  • Primary Vision Cortex: around 4-8 months
  • Primary Frontal Cortex: second year
33
Q

What happens during Myelination?

A
  • Rough parallels functional development
  • Sensory Areas: first few months
  • Motor Areas: soon after sensory areas
  • PFC: continues into adolescence
34
Q

What happens during regressive changes (pruning)?

A
  • Periods of synaptic loss/refinement
35
Q

What happens during postnatal development of the Prefrontal Cortex?

A

Relatively Slow, more gradual development, continuing into late adolescence.

Linked to parallel development of “higher” cognitive executive functions

36
Q

What are four executive functions of the PFC?

A
  1. Working memory (temporary memory used while a task is being performed)
  2. Planning and carrying out sequences of actions
  3. Following rules for social behaviours
  4. Context dependent inhibition of inappropriate responses “time and place”

PSYCH 3410 (10 decks)

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