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BCB > S1W11Dev > Flashcards

S1W11Dev Flashcards

1
Q

Step 1 neural tube from a neural plate

A

Neural plate = 16 day gestation.

Neural tube = 22 day gestation.

NT closes and forms brain and spinal cord = 27 days gestation.

Centre of NT becomes ventricles of brain filled with CSF.

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2
Q

Neural progenitor cell

A

Line inner part of NT.

Differentiates into specific type of cell, but is already more specific than stem cell.

Some cells separate to form the neural crest which makes the PNS.

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3
Q

Cerebrospinal fluid (CSF)

A

Fills centre of CSF.

Mechanical and immunological protection to brain.

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4
Q

Neural tube defects causes

A

Neural tube fails to close properly

Exposure of part of brain and/or spinal cord

Varying degrees of bone and neurological involvement (can be fatal)

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5
Q

Craniorachischisis

A

Completely open brain and spinal cord.

Fatal.

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6
Q

Anencephaly

A

Open brain lack of skull vault.

NT fails to seal at the head of embryo.

Forebrain fail to develop.

Fatal.

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7
Q

Encephalocele

A

Herniation of meninges and brain.

Retardation and vision problems.

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8
Q

Iniencephaly

A

Occipital skull and spine defects with retroflexion of head.

Fatal.

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9
Q

Meninges

A

Membranes

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10
Q

Spina bifida

A

Neural tube fails to seal at lower end.

Different types.

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11
Q

Spina bifida occulta

A

Some vertebrae not closed.

No cord protrusion .

Symptomless.

50% of population have it and are unaware.

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12
Q

Closed spinal dysraphism

A

Deficiency of 2+ vertebral arches.

Unlikely to cause problems on its own.

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13
Q

Meningocele

A

Protrusion of meninges through skull or spine defect.

Mild problems.

Filled with CFS and not spinal cord parts.

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14
Q

Myelomeningocoele (Open spina bifida)

A

Protrusion of spinal cord.

Severe complications.

Poor walking, bowel control.

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15
Q

Step 2 (1) (three vesicles)

A

Cranial (front) part NT becomes (5 weeks):

Hindbrain (rhombencephalon)

Midbrain (mesencephalon)

Forebrain (proencephalon)

Caudal (back) part NT becomes spinal cord.

Fluid fills spinal cord canal and ventricles.

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16
Q

Further division of three vesicles

A

Vesicles enlarge and divide into:

Forebrain:
Telencephalon
Diencephalon

Midbrain:
Mesencephalon

Hindbrain:
Metencephalon
Myelencephalon

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17
Q

Telencephalon

A

Cerebral cortex

Basal ganglia

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18
Q

Diencephalon

A

Thalamus

Hypothalamus

(forebrain)

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19
Q

Mesencephalon

A

Colliculi

midbrain

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20
Q

Metencephalon

A

Pons

Cerebellum

(hindbrain)

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21
Q

Myelencephalon

A

Medulla

hindbrain

22
Q

Forebrain

A

Cerebrum
Thalamus
Hypothalamus

23
Q

Hindbrain

A

Pons
Medulla oblongata
Cerebellum

24
Q

Step 3 – Neuronal development

A

Walls of NT contain stem cells, which drive brain growth by dividing.

Stages:
•	Proliferation
•	Migration
•	Differentiation
•	Synaptogenesis
•	Myelogenesis
25
Q

Stem cells

A

Undifferentiated cells that differentiate into specialised cells or divide (mitosis) to produce more stem cells.

26
Q

Proliferation

A

42 days gestation.

Neural progenitor cells either:

  • Stay in choroid plexus.
  • Continue to divide into neurons and glial cells.

Peak proliferation rate = 250k neurons/minute.

22 weeks gestation neurogenesis complete apart from olfactory bulb hippocampus.

27
Q

Glial cells

A

Surround neurons and hold them in place.

Supply oxygen and nutrients to neurons

Destroy pathogens/dead neurons.

28
Q

Migration

A

Neural progenitor cells migrate at different rates and directions, aiming to reach the target cell in up to four days.

Migrate up to 2cm.

29
Q

Sperry’s Newt (1940)

A

How do cells know where to go?

Cut optic nerve of newts and rotate the eye 180 degrees.

Axons grew back to original places but newts saw upside down.

Axons are guided by gradient of proteins called neurotrophins.

Numerous synapses made in target then synaptic pruning removes.

30
Q

Differentiation

A

Neural progenitor cells take on characteristics of specific neuron.

Formation of axon and dendrites.

Acquisition of enzymes to produce neurotransmitters.

Acquisition of receptors to receive synaptic transmissions.

31
Q

Synaptogenesis

A

Formation of synapses

Lifelong but slows with age

1-2yo – peak synapse formation - twice as many connections as adults.

Synaptic pruning

32
Q

Axon differentiation

A

Grows first

Tip of axon = growth cone (site of elongation and extension).

Growth cones sample local environment for molecules that direct growth.

Axons can grow whilst migrating.

33
Q

Dendrite differentiation

A

Grows once neuron reaches target.

Grows slower than axons.

34
Q

Myelogenesis

A

Myelin surrounds axon forming insulating sheath

Oligodendrocytes form myelin in CNS (Schwann cells in PNS).

Process:
Spinal cord > 
Hindbrain >
Midbrain >
Forebrain
•	Takes years
35
Q

Other functions of oligodendrocytes

A

Produce trophic factors that maintain axonal integrity and neuronal survival.

Neuron/Oligodendrocyte interactions influence neuronal size and axon diameter.

36
Q

Regressive events in neuronal development

A 
Brain overproduces:
o Neurons (peak at 7mo)
o Synapses (peak at 1-2yo at 15,000)

Regression results in thinning of cortex associated with behavioural development.

Apoptosis and Pruning.

37
Q

Apoptosis (programmed cell death)

A

Prenatal.

Reduces neurons

Results in loss of cell and all synapses

Neuron dies

Maximal during late prenatal stage (reduces 28bil to 23bil by birth)

Triggered by lack of neurotrophins released from postsynaptic cell.

38
Q

Synaptic pruning

A

Postnatal

Reduces synapses

Neuron survives

Three methods:
o Axon degeneration
o Axon retraction
o Axon shedding

All result in axon removal and deletion of synapse

Triggered by hormones and neurotrophins.

39
Q

Hebb Rule (1949)

A

What determines which synapses are pruned?

States that the connections between two neurons might be strengthened if the neurons fire simultaneously.

40
Q

Embyronic stage development

A

Conception to week 8 gestation.

Rudimentary structures of brain produced

Major compartments of CNS and PNS defined

Neuron production starts at week 6 gestation

41
Q

Foetal stage development

A

Week 9 gestation to birth

Characteristic pattern of gyral and sulci folding.

Development of neocortex.

Neurogenesis, migration and differentiation.

Neuronal cell loss.

42
Q

Newborn brain

A

One quarter of adult size

Spinal cord and brain stem well developed

Limbic system and cerebral cortex still primitive

43
Q

Birth to toddler years

A

Synaptogenesis in cerebral cortex(exuberant period)

At peak cerebral cortex creates 2 million synapses/second.

Corresponds with mental milestones

Myelination rapid in first 2 years.

2yo - brain 80% of its adult size

44
Q

Toddler to adolescent

A

Too many synapses in cerebral cortex in childhood

Synaptic pruning increases 4-6yo

Brain 90% adult size by 6yo

45
Q

Adolescence (13-18yo)

A

Synaptic pruning until end of adolescence

Grey matter decreases in volume

Myelination continues especially in frontal cortex

White matter increases in volume

Prefrontal cortex matures later than limbic system

Creates neural imbalance

Theorised to be one reason for teen impulsiveness

Brain adult weight

46
Q

End of adolescence to 60s

A

Brain peak power at 22yo for 5 years

Then:

Cortex becomes thinner

Myelin sheath degrades

Decrease in plasticity

Decrease memory, reasoning, spatial skills and thought speed

Changes minimal in healthy individuals

47
Q

60s onwards

A

65+ years elderly for experiments

Brain shrinks in size

Myelin sheath degrades

Blood flow to brain decrease

Damage by free radicals increases

Decrease in memory, ability to learn, attention, reasoning.

48
Q

Dementia

A

Vascular (20-30%)

Lewy Bodies (10-25%)

Frontotemporal (10-15%)

Alzheimer’s (50-75%)

Anatomically:

Plaques (outside neuron)
Tangles (inside neuron)

49
Q

Nature vs. Nurture

A

Nature:

Genes guide brain set-up
Provide information for cells and general connections

Nurture:

Experience responsible for fine tuning

50
Q

Prenatal nutrition

A

Maternal diet important

Low calories = decreased foetal neural development

Low Omega 3 = poor infant neural development

Severe maternal iodine deficiency = mental deficiency (cretinism)

51
Q

Postnatal nutrition

A

Child’s own diet important

Iron deficiency = poor STM encoding or retrieval

Inadequate calories and protein = smaller brains due to reduced dendritic growth, myelination and glial cells

BCB (19 decks)

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