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BS450 > Chapter 23: Wiring the Brain > Flashcards

Chapter 23: Wiring the Brain Flashcards

1
Q

brain development begins as ()

A

tube

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2
Q

wiring in the brain is determined by:
1. nature - ()
2. nurture - ()

A
  1. establishing correct pathways and targets by genetic programs
  2. fine-tuning based on experience and sensory info from envi
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3
Q

organization of the LGN

inputs are segregated by ()

A

eye and ganglion cell type

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4
Q

() cells give rise to neurons and astrocytes.

A

Radial glial

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5
Q

neuronal cell structure developes in 3 major stages

A
  1. cell proliferation
  2. cell migration
  3. cell differentiation
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6
Q

In humans, the majority of neocortical neurons are born between the () of gestation, peaking at the astonishing rate of 250,000 neurons per minutes

A

5th week and the 5th month

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7
Q

cell proliferation

(1) and (2) during cell division determine fate of daughter cells.

A
  1. Transcription factors
  2. cleavage plane
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8
Q

Ultimate fate of migrating daughter cells determined by the (1) of the precursor cell, its (2), and its (3) at the time of division.

A
  1. age
  2. position
  3. environment
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9
Q

cell migration

() migrate vertically from the dorsal ventricular zone by moving along thin radial glial fibers.

A

Pyramidal cells and astrocytes

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10
Q

cell migration

() generate from the ventral telencephalon and migrate laterally.

A

Inhibitory interneurons and oligodendroglia

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11
Q

cell migration

Radial processes disappear when () is complete

A

cortical assembly

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12
Q

cell migration

  • First cells to migrate take up residence in (1), which eventually disappears.
  • Next cells to divide migrate to the (2).
  • The first to arrive become layer VI, followed V, IV, and so on: “(3).”
A
  1. subplate layer
  2. cortical plate
  3. inside out
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13
Q
  • Consequence of a specific spatiotemporal pattern of gene expression
  • process by which a cell takes on the appearance and characteristics of a neuron
A

cell differentiation

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14
Q

Order of cell differentiation: ()

A

neurons, astrocytes (peaks at the time of birth), then oligodendrocytes

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15
Q

evidence for idea that cell differentiaton is rogrammed well before reaching final destination

A

neural precursor cell will still differentiate even when extracted from brain and placed in tissue culture

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16
Q

(), a protein secreted by cells in the marginal zone, repels the growing axon and attracts the growing apical dendrite, giving the pyramidal neuron its characteristic polarity.

A

Semaphorin 3A

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17
Q

Adult cortical sheet like a “()”; many structurally distinct areas stitched together; in humans, many specialized cortical areas are precisely stitched

A

patchwork quilt

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18
Q

Ventricular zone contains cortical ‘()’; migrating cells are precisely guided by radial glial fibers (for majority of cortical neurons)

helps for “patchform quilt” arrangement of cortical sheet

A

protomap

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19
Q

Some (~1/3) neurons migrate laterally. How? Neurons in different areas have distinct ().

A

molecular identities

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20
Q

() input contributes to cortical differentiation

A

Thalamic

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21
Q
  • concept that an entire radial column of cortical neurons originates from the same birthplace in the ventricular zone
A

radial unit hypothesis

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22
Q

In the fetal telencephalon, () are expressed by neural precursor cells in complementary gradients

  • sizes of different cortical areas change when these concentration gradients are also changed
A

Pax6 and Emx2

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22
Q

describe how thalamic inputs are able to influence cortical development

A

Subplate neurons attract appropriate thalamic axons

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22
Q

3 phases of pathway selection

(1) : which side of the optic tract?
(2) : which nucleus of the thalamus?
(3) : which layer of the LGN (with topography)?

A
  1. Pathway selection
  2. target selection
  3. address selection
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23
Q

(): growing tip of a neurite

A

Growth cone

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24
Q

(): constantly probe the environment and direct the
growth of the neurite towards attractive cues.

A

Filopodia

25
Q

Neurite growth occurs when a filopodium binds the () and pulls the growth cone forward

A

substrate (the surface on which it is growing)

26
Q

Filopodia bind appropriate proteins, such as laminin, in the ()

A

extracellular matrix (growing axons express integrin that binds laminin)

27
Q

(): permissive substrates bordered by repulsive ones

A

Molecular “highway”

28
Q

(): process of growing axons sticking together by cell adhesion molecules, CAMs, forming bundles of axons

A

Axonal fasiculation

(“fascicles”) = bundles of axons

29
Q

() stretch as nervous system expands.
- Guide neighbor axons to same targets

A

Pioneer axons

30
Q

Pioneer neurons grow in the correct direction by “()” (a few hundred microns long).

A

connecting the dots

31
Q

The pioneering axon concludes a segment when it arrives at an (). The interaction of the axon and the () throws a molecular switch that sends the axon onward to another ().

A

intermediate target

32
Q

Growth cones differ in terms of the molecules they express on their membranes -> Interactions of these () with guidance cues in the environment determine the direction and amount of growth

A

cell surface molecules

33
Q

diffusible molecules that act over a distance to attract growing axons toward their targets

A

Growth guidance cues

33
Q

examples of growth guidance cues

A

chemoattractant (e.g., netrin), chemorepellent (e.g., slit)

34
Q

The protein called netrin is secreted by cells in the ventral midline of the spinal cord. Axons with the appropriate netrin receptors are (attracted to/repelled from) the region of highest netrin concentration.

A

attracted to

35
Q

The protein called (1) is also secreted by midline cells. Axons that express the protein called (2), the (1) receptor, grow away from the region of highest (1) concentration

A
  1. slit
  2. robo

Up-regulation of robo by axons that cross the midline ensures that they keep growing away from the midline.

36
Q

(): chemical markers on growing axons are matched with complementary chemical markers on their targets to establish precise connections

A

Chemoaffinity hypothesis

37
Q

Large-scale () in neurons and synapses during the process of refining connections (from before birth all the way through adolescence)

A

reduction

38
Q

proper development of brain function requires balance between ()

A

genesis and elimination of cells
and synapses

39
Q

Autism spectrum disorder: () disorder

A

neurodevelopmental

40
Q

Cell death reflects competition for () provided by the target cells; life-sustaining substances that are provided in limited quantities

A

trophic factors

41
Q

(): identified in 1940s (released by targets of sympathetic neuronal axon) -> example of trophic factor

A

Nerve growth factor (NGF)

42
Q
  • (): NT-3, NT-4, BDNF, etc. Bind to trk receptors (tyrosine kinase) altering gene expressions -> family of proteins, including NGF
A

neurotrophins

43
Q

programmed cell death; cell death genes are expressed (normally suppressed by trophic factors)

A

apoptosis

44
Q

(): the number of synapses a neuron can receive

A

Synaptic capacity

45
Q

(): change from one pattern of synaptic connections to another

A

Synaptic arrangement

involved in critical period

46
Q

Synaptic arrangement is a consequence of (2)

A

neural activity and synaptic transmission

both before (spontaneous activity) and after (sensory experience during childhood) birth

47
Q
  • In some circuits, final refinement of synaptic connections requires ()
A

neural activity

48
Q

(): whenever a wave of retinal activity drives a postsynaptic LGN neuron to fire action potentials, the synapses between them are stabilized

A

Hebbian modification -> strengthened synapses are called Hebbian synapses

49
Q

Visual cortex has () (cat, monkey)—segregated input from each eye (by molecular cues + activity difference)

A

ocular dominance columns

50
Q

(): a period after birth when the ocular dominance columns may be modified by activity dependent plasticity (monkey: ~6 wk).

A

Critical period

dependent on experience

51
Q

Inputs from two eyes must be combined for () -> Convergence of inputs from layer IV neurons serving the left and right eyes in layer III

A

binocular vision

51
Q

(): formed by correlated patterns of activity from two eyes as a consequence of vision (c.f., ocular dominance columns by asynchronous activity from two eyes)

A

Binocular receptive fields

52
Q

(): disrupts binocular connections, results in ocular dominance shift

shift may occur within hours (synaptic changes without substantial remodeling of axons)

A

monocular deprivation

53
Q

(): inputs from two eyes actively compete for synaptic control of postsynaptic neurons

A

Binocular competition

54
Q

(): eyes are not perfectly aligned so that one eye is turned in a direction different from the other eye (cross-eyed or wall-eyed)

A

Strabismus

55
Q

Two rules for synaptic modification

A

– Fire together, wire together (Hebbian modifications)
(pre + strong postsynaptic activation)
– Fire out of sync, lose their link
(pre + weak postsynaptic activation)

56
Q

A single synapse has little influence on firing rate of postsynaptic neuron -> Activity of a synapse must be () with activity of many other inputs converging on the same postsynaptic neuron for strong postsynaptic activation

A

correlated

56
Q

Focus on two glutamate receptors

  1. () receptors: glutamate-gated ion channels
  2. () receptors: have unique properties
A
  1. AMPA
  2. NMDA
57
Q

2 unique properties of NMDA receptors

A

– Voltage-gated owing to action of Mg2+ (magnesium block)
– Conducts Ca2+

58
Q

Magnitude of Ca2+ flux into axon terminal signals level of ()

A

pre- and postsynaptic coactivation

BS450 (11 decks)

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