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Brain and behaviour > Brain Development and Plasticity > Flashcards

Brain Development and Plasticity Flashcards

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The Brain flashcards
1
Q

What are the 3 key steps in making a brain?

A
  1. Form a neural tube from neural plate.
  2. Form a primitive brain.
  3. Neuronal development.
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2
Q

What happens during stage 1 of forming a brain (form a neural tube from neural plate)?

A
  • Neural plate forms 16 days post conception.
  • Plate lengthens and folds into neural tube (22 days gestation).
  • Neural tube fully closed & begins to form into brain and spinal cord (27 days gestation).
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3
Q

What lines the inner part of the neural tube?

A

Neural progenitor cells.

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4
Q

Making a brain: What happens in the neural tube?

A

centre of tube will become ventricles of brain filled with cerebrospinal fluid.

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5
Q

What does cerebrospinal fluid provide?

A

Mechanical and immunological protecting to the brain inside the skull.

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6
Q

When the Neural tube defects occur?

A
  • If the neural tube fails to close properly.
  • Exposure of part of brain and/or spinal cord.
  • Exposed part vulnerable to damage.
  • Varying degree of bone and neurological involvement (can be fatal)
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7
Q

What happens in step 2 in formation of the brain (form a primitive brain)?

A

Cranial (front) part of the neural tube enlarges and differentiates into the fore, mid and hindbrain.

This is completed by approx. 3-4 weeks.

Caudal (back) part of the neural tube becomes the spinal cord.

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8
Q

What are stem cells?

A

Undifferetiated cells that can differentiate into more specialised cells and divide to produce more stem cells.

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9
Q

What is a progenitor cell?

A

Like a stem cell - it differentiates into a specific type of cell, but is already more specific than a stem cell.

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10
Q

What happens in stage 3 of brain development (neuronal development)?

A
  • Proliferation (neurogenesis/gliogenesis)
  • Migration
  • Differentiation
  • Synaptogenesis (formation of synapses)
  • Myelogensis (formation of myelin)
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11
Q

When does proliferation occur?

What is proliferation?

A

42 days post conception.

Neural progenitor cells have 2 fates - they continue to divide into either primitive neurons/glia

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12
Q

What are glial cells?

A

Surround neurons and hold them in place, supply nutrients and oxygen to neurons, neurons from each other, destroy pathogens and remove dead neurons.

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13
Q

When is peak proliferation?

A

250,000 neurons formed per minute.

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14
Q

When is most neurogenesis complete?

With what exceptions?

A

5 months post conception

Olfactory bulb and hippocampal cells.

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15
Q

In migration, what do axons follow?

What are axons guided to and what by?

How specific is target location?

What does synapse pruning do?

A

A chemical trail to find their target location.

Axons are guided to approximate location by gradient of proteins called neurotrophins.

Not very, only approximate.

Reduces unwanted synapses.

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16
Q

What is differentiation?

What does differentiation involve?

A

Stage when a neural progenitor cell begins to take on appearance & characteristics of a specific neuron.

  • Formation of axon and dendrites
  • Acquisition of enzymes required to produce neurotransmitters.
  • Acquisition of receptors to receive synaptic transmissions.
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17
Q

what is synaptogenesis?

A
  • Formation of synapses
  • Lifelong but slows as ageing.
  • 1-2yrs old = peak synapse formation.
  • Twice as many connection than the adult brain -> synaptic pruning.
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18
Q

What surrounds the axon?

A

Myelin, forming an electrically insulating sheath.

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19
Q

What forms Myelin in the CNS?

A

Oligodendrocytes

Starts in spinal cord -> hind brain - mid brain - forebrain.

Slow process e.e., 10-12 years after birth.

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20
Q

Give 2 functions of oligodendrocytes in brain developed?

A
  • Produce trophic factors that help maintain axonal integrity and neuronal survival.
  • Neuron-oligodendrocyte interactions influence neuronal size and axon diameter.
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21
Q

When do the number of neurons peak?

A

7 months.

22
Q

How old are you when synapses peak?

A

1/2years old.

23
Q

Regressive events during neuronal developmental: prenatally, what reduces neurons?

A

Apoptosis - resulting in loss of the cell and all its synapses and processes.

Neuron dies.

Results in thinning of cortex.

24
Q

Regression events during neuronal development: postnatally, what reduces neurons and connections?

A

Synaptic pruning

Neuron survives.

Results in thinning of cortex.

25
Q

What is cortical thinning correlated with in most brain regions?

A

Behavioural development.

26
Q

What apoptosis?

A

Programmed cell death.
Removes unwanted neurons in a controlled manner.
Macimal during late prenatal stage - reduces 28 billion neurons to 23 billion by birth.

27
Q

What triggers apoptosis?

A

Neurotrophins released from postsynaptic cell -> neurons live (neurotrophins cancel apoptopss).

No neurotrophiins released from postsynaptic cell -> neuron dies via apoptosis -> dying cells removed by glial cells.

28
Q

What brain development occurs in the embryonic stage (conception to week 8 gestation)?

A
  • Rudimetary structures of the brain produced
  • Major compartments of central & peripheral nervous systems defined.
  • Neuron production starts week 6 gestation.
29
Q

What brain development happens in the foetal stage?

A
  • Characteristics pattern of gyros and sulci folding.
  • Development of the neocortex.
  • Brain development focuses on neurogenesis, migration & differentiation.
  • Neuronal cell loss.
30
Q

How big is the new born brain?

What parts of the brain is well developed?

What parts of the brain are still primitive?

A

1/4 of its adult size.

Spinal cord and brain stem well developed.

Limbic system and cerebral cortex still primitive.

31
Q

In birth to toddler years, how many synapses does the cerebral cortex create?

A

2,000,000 synapses/sec.

32
Q

When is myelination most rapid?

A

First 2 years.

33
Q

At what age is the brain 80% of its adult size?

A

2 years.

34
Q

When is the brain at 90% of adult size?

A

Age 6.

Over-abundant amount of synapses in all areas of the cerebral cortex exists throughout middle childhood.

Synaptic pruning increases.

35
Q

When is synaptic pruning maximal?

A

1-2yrs.

36
Q

What are the 3 main methods of synaptic pruning are proposed?

A
  1. Axon degeneration
  2. Axon retraction
  3. Axon shedding.

All result in axon removal and subsequent deletion of synapse.
Hormones and neurotrophins likely to play a major role in process.

37
Q

What is Hebbs rule regarding synapse pruning?

A

Neurons that fire together, wire together.

38
Q

Adolescence (13-18) How long does synapse pruning go on for?

A

Synaptic pruning continues until end of adolescence - grey matter decreases in volume.

39
Q

Adolescence (13-18) Where does myelination continue into?

A

The frontal cortex - white matter increases in volume

40
Q

What matures first, the limbic and rewards systems or the prefrontal cortex?

What is this theorised to be the reason of?

A

The limbic and rewards systems.

Teen impulsivensss.

41
Q

How heavy if the adult brain?

A

3lbs.

42
Q

What age is the brain at its peak power?

A

22 and lasts for 5 years.

43
Q

After age 27, the brain goes downhill - what happens?

A
  • Cortex becomes thinner
  • Myelin sheath beings to degrade
  • Decrease in brain plasticity
  • Chemical changes

Decrease in:

  • Memory
  • Reasoning
  • Spatial skills
  • Speed of thought.
44
Q

What happens to the brain in the 60s?

A

Increase in anatomical and functional changes in the brain:

  • Brain shrink in size
  • Myelin sheath degrades
  • Chemical change
  • Blood flow to brain may reduce
  • Damage by free radicals increases.
  • Memory
  • Ability to learn
  • Attention
  • Reasoning
  • Spatial skills
  • Speed of thought.
45
Q

What is dementia?

A

A set of symptoms that may include persistent disorder of the mental processes caused by brain disease or injury and marked by memory disorders, personality changes and impaired reasoning.

46
Q

Do our brains stop developing?

A

Yes if considering structural and functional aspects e.g., brain size, speed of neural processing.

No, if consider neuroplasticity.

47
Q

What is neuroplasticity?

A

The capacity of the nervous system to reorganise itself by forming new neural connections.

48
Q

Categorising neuroplasticity: what are the different categories?

A
  • Synaptic (LTP and LTD)
  • Structural (changes in the wiring of the brain)
  • Developmental (apoptosis, synaptic pruning).
  • Injury-induced.
  • Types of plasticity in children e.g., language and vision.
49
Q

Many neuroplasticity mechanisms underlie learning & memory, what are these?

A
  • strengthening of existing synapses.
  • formation of new synapses
  • elimination of old synapses
  • modification of dendritic branches.
50
Q

Injury-induced Neuroplastiicty: human studies, give an example.

How many participants?

What was treated?

What was tested?

What were the results?

What are the conclusions?

A

Boatman, 1999:

  • 6 children, 7-14yrs with Rasmussen’s syndrome
  • Treated by left hemisphere
  • Tested language capabilities of remaining right hemisphere.

16 days post surgery:
Improved phoneme discrimination compared to pre-surgery state. Remaining language functions severely impaired.

1 year post surgery:
Naming still impaired & speech limited to single words BUT single word & phrase comprehension same/better than pre-surgery, word repetition intact.

Conclusions:
NP in the right hemisphere enabled recovery of many aspects of language acquisition despite children being beyond proposed ‘critical period’ for language acquisition.

51
Q

What causes phantom limb sensation/pain?

A

Reorganisation of the somatosensory and motor cortices following limb removal results in altered representations of neighbouring body parts.

52
Q

Give an example of phantom limb pain

A

Upper limb amputation.

Expansion of the cortical representation of the face into the area where the amputated upper limb used to be represented.

Increased incidence and severity of phantom limb sensation/pain.

However, currently unclear why expansion caused increased sensation/pain.

Brain and behaviour (9 decks)

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