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Neuroscience > The Developing Brain (Chapter 6) > Flashcards

The Developing Brain (Chapter 6) Flashcards

1
Q

Neuron Development

A
  • while embryo gorws
  • singaling molecules “turn on” certain genes and “turn off” others
  • this intiates the formation of immature nerve cells
  • cell division (proliferation), brain cells increase by billions
  • migration= newly formed neruons travel to final destinations
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2
Q

three layers emerging during embyronic development

A
  • the ectoderm(outer-most layer), the mesoderm(middle layer), the endoderm(inner-most layer)
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3
Q

cells in each of the three layers

A
  • contain identical DNA instructions for development

- these layers give rise tot he rich variety of tissue types that make up the human body

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4
Q

what is the cause behind the diversity of these tissue types?

A
  • singals produced by surrounding tissues

- signals turn certain genes on, others off to induce the development of specific cell types.

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5
Q

nerve tissue is formed…

A
  • signals from the mesoderm trigger some ectoderm cells to be come it
  • called nerual induction
  • after, subsequent signalling interactions regine the nerve tissue into basic categories (neurons/glia), and then subclasses of each cell type
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6
Q

what is the fate of a developing cell largely dependent on

A
  • its proximity to various sources of signaling molecules
  • ## concentration of each signalling moleucel type decreases farther from the source to create gradietns in the brain
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7
Q

sonic hedgehog

A
  • secreted from mesodermal tissue beheant the developing spinal cord
  • a signaling molecule
  • exposure to the signal causes adjacent nerve cells to be converted into a special class of glia
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8
Q

what happens when cells are farther away from the singal

A
  • exposed to lower ceoncentraitions of sonic hedegog, so they become motor neruons that control the movement of muscles
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9
Q

even lower concentraition (farther awar)

A
  • they become interneruons which do not relay messages to muscles but to other neurons
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10
Q

where do neruons arise from

A
  • afarily small pool of nerual stem and proentior cells
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11
Q

progentior cells

A

special cells that an divide and become a variety of mature cell types.

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12
Q

when does the human brain begin to form

A
  • after three week’s gestation
  • first stage is nerual tube,
  • by four weeks, the individual sections of brain can be recognized
  • by 6 months, the ridges of the brain can be observed.
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13
Q

before cells become a variety of mature cell types, what has to happen>

A
  • before achieveing their mature cell fate, this pool of cells must undergo a series of divisions to increase the number of cells that will ultimately form the brain.
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14
Q

early cell dicision

A
  • are symmetrical- reuslts in two identical daughter cells that have the capacity to continue to divide
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15
Q

what happens as cell divisions begin to rpogress

A
  • cells begin to divide asymmetrically
  • give rise to one daughter cell that continues to rapidly divide
  • second daughter cell progresses towards its final cell fate as a nerual or glial cell
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16
Q

proliferative process

A

permits rapid growth during early development of the brain

- billions of cells are produced in a matter of weeks

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17
Q

what happens after that series of cell divisions is complete?

A
  • onyl few nerual stem and progenitor cells remain within the brain
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18
Q

neurogensis in adulthood

A
  • is limited to a few regions of the brain, such as those involved in mmeory
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19
Q

protein defects

A
  • cause premature switch from symmetric to asymmetric divisions
  • this may be the cause of microcephaly
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20
Q

microcephalt

A
  • severe reduction of rbain size,
  • associated with serious neurological disabilityies
    sometimes death in infancy
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21
Q

excessive proliferation of brain cells

A
  • can lead to a disorder called megalencephaly
  • brain is abnormally large and heavy
  • associated with a variety of neurodevelopmental complications
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22
Q

induction

A
  • those signals that turn certain genes on and others off induce the developemtn of specific cell types
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23
Q

waht happens after 1) induction and 2) proliferation

A
  • migration
  • new neurons journey from inner surface of embryonic brain to their long-term locations in the brain
  • begins three to four weeks after a human baby is conceived
  • ectoderm starts tot chicken and build up along the midline of the emrbyo
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24
Q

what happens afger the ectoderm starts to thicken

A
  • cells continue to divide
  • flat heural plate grows
  • formation of parallel ridges (like a paper airplane) that rise along either side of the midleine
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25
Q

ridges on the sides of the midline

A
  • extend from the “head end” where the future brain will form
  • they are along the elenth of the embryo where the future spinal cord will develop
  • few days, the ridges fold toward each other and fuse into a hollow nerual tube
26
Q

waht happens to the head end of the neural tube

A
  • it startes to thicken
  • tforms three bulges
  • they are the hindbrain,t he midbrain, and the forebrain
27
Q

7 weeks affter gestation>

A
  • first signs of the eyes and the brain’s hemispheres appear
28
Q

what hpapens after new neruons are produced (after eyees, and hemispheres start to appear)

A
  • they move from the nerual tube’s ventricular zone (inner surface of the tube) towards the border of the marginal zone (outer surface)
29
Q

what happesn after neruons stop diciding

A
  • they form an intermediate zone where they gradually accumulate as the brain develops
30
Q

how do neurons know wehre they must go? (final destination)

A
  • guidance cues
  • radial glia
  • they project radially from the intermediate zone to the cortex
  • neruons inch along glial projections until they reach their final destinations
  • cells that arrive the earlier are the oldest ones that form the deepest layer of the cortex
  • late-arricing are the youngest neurons that form the outermost layer
31
Q

another mechanisms for guiadance

A
  • neurons migrate sideways or tangentially (rather than radially), moving parallel to the brain’s surface and across the radial cortical columns
32
Q

what can infleunce migration

A
  • exposure to alcohol, cocaine, or radiation can prevent proper migration, resulting in misplacement of cells
  • ## misplacement can lead to intellectual ability, or epilepsy
33
Q

what happens when there are mutations in the genes that regulate migration

A
  • can cause rare genetic forms of intellectual disability and epilepsy in humans
34
Q

what happens when neruons reach their final lcoations

A
  • ## they begin making the connections that will determine how particular functions (e.g. vision and hearnign) can occur
35
Q

internal processes of fetal development

A
  • induction, proliferation, and miogration
36
Q

external phases of brain development

A
  • occur afterbirht
  • factors such as watching a mobile spin, listening to a voice, and even proper nutrition can influence the connections formed by neurons
37
Q

how do neurons become interconncented

A
  • through their short branches called dendrites and long azons (can occur after birth from external factors)
38
Q

axon length

A
  • in order to reach their targets, axons can span distance many times the size of their cell body, many corsssing to the opposite side od the brain
39
Q

longest human axons

A
  • in the periphery

- they extend from the lower spnial cord all the way to muscles in the toes

40
Q

how does a developing axon grow

A
  • through the extension of its growht cone

- it actively explore the environment to seek out its precise destination

41
Q

how is the gorwht cone guided to final destination

A
  • molecular clues in its envionrments
  • some molecules are on the srugace of cels while others are secreted into areas near the growh cone
  • receptors no the gorwh cone enable its response to these environmental cues.
42
Q

signaling molceules taht make up molecular cues

A
  • families of proteins with names such as netrin, semaphoring, and ephrin
  • these are found in many organisms such as worms, insectes and mammals although it may be of a smaller concentration in flies or worms than in mice or poeprle- but functions are still similar
43
Q

what happens when axons reaches its destination

A
  • a synpase begins to form
44
Q

neurotransmittters

A
  • can either promtore or hinder the generation of a new electrical signal in the receiving neuron
45
Q

how many synapses does our brain contain

A

trillions

46
Q

what has to happen, in order to allow the brain to process complex info

A

the formaion of synaptic connections must be highly specific

- specificity is partly because of the mechanisms that guides the axons to their proper targets

47
Q

how is the synpase anchored

A
  • dendrites and axons both produce proteins that span the space between them and anchor the snyapse togehter
48
Q

differentation after establishment of a synapse (presynaptic)

A
  • tiny axon termioanl that contacts the dendrite becomes specialized for releasing neurotransmitters
  • stocks itself with neurotransmitter packets and proteins that enable the packets to be held in place and then realeased
49
Q

differentiation post-synaptic

A
  • receptors that repsond to those neruotransmitters begin to dot the membrane
  • ensures that a synpase can transmit signals quickly and effectively.
50
Q

strocytes

A
  • type of flial cell in the brain
  • previously thought to simply provide scaffolding an passive support to neurons
  • they exert their own influence on synaptic development and function
  • many synpases in the brain are contacted by astrocytes]
  • contact thousands of synapses across multiple neruons
51
Q

astrcotyes two

A
  • neurons orm only few synapses when developing in a culture dish when astrocytes are absent
  • molecules secreted by astrocytes regulate aspects of synaptic development
52
Q

what defects could contribute to autism

A
  • molecules from multiple sources work together to promote proper synpase formation
  • defects in such molecules could contribute to such disorders
53
Q

what could underlie the degradation that occurs udrig aging

A
  • the loss of certain other molecules
54
Q

what determines the type of neruotransmitter a neruon will use to commmunciatie

A
  • for some cells such as motor neruons, they will always use acetlycholine
55
Q

neurotransmitter

A
  • when certain immature neruons are maintained in a culture dish w/o any other cell types, they produce NOREPINEPHRINE
  • when same neruons are culkutred with specific cells e.g. cardiac tissue they produce acetlycholine
56
Q

what infleunces the signal signals that engages the gene and the final determination of the chemical messenger a neruon will produce

A
  • influenced by factors that come from the location of the synapse itself.
57
Q

myelination

A
  • the fatty wrapping of axons by extension so flia

- increases by as much as 100 times the speed at which signals can travel along axons

58
Q

nodes of Ranvier

A
  • the way they are wrapped increases the speed

- regularly spaced gaps of the sheath they interrupt the sheath

59
Q

nodes of Ranvier for speed

A
  • alternating pattern of insulation and nodes allows electrical signal to move down an axons faster, from one node to the next
60
Q

saltatory conduction

A
  • the alternating pattern of inslulation and nodes is responsible fo more rapid transmission of electrical signals
61
Q

when does formation of meyelin occur

A

througout the lifespan

Neuroscience (7 decks)

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