Singh 1: Development of the Nervous System Flashcards

1
Q

Key Concepts in Early Development:

Initially all neural cells are ______ but all end up having ______

A

Initially, all neural cells are equivalent but all end up having unique identities.

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2
Q

Key concepts in early development:

Regionalization and specificity arise due to ______________

Regionalization arises ____ and dictates ____

A

Regionalization and specificity arise due to differential exposure to gradients of signaling molecules (space/time)

Regionalization arises early and dictates identity and adult function

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3
Q

Key concepts in early development:

The CNS develops from a ______ of cells that ______ into a tube

The tube _____, _____ and _____

Some parts of the tube ______

A

Key concepts in early development:

The CNS develops from a flat plate of cells that rolls up into a hollow tube

The tube bulges, flexes and grows

Some parts of the tube grow more than others

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4
Q

Major events in early nervous system development:

What happens by 3-4 weeks?

What happens by 6 weeks?

A

3-4 weeks: neural plate develops, brain vesicles form, neural tube forms, and tube bends

By 6 weeks: secondary vesicles form, and the tube bends again

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5
Q

What are the three germinal layers that form the embryonic disc?

What does each develop into?

A

Three Germinal Layers that form the Embryonic Disc:

  • Endoderm: develops into gut lining and respiratory tract
  • Mesoderm: develops into muscular system, skeletal system and vascular system
  • Ectoderm: develops into CNS (also epidermis of the skin)
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6
Q

Explain via diagram how the neural plate becomes a tube

A

Look at the diagram

You have a flat body of cells called the neural plate. They get signaled by the notochord underneath to differentiate and divide. They get thicker and thicker and start to invaginate and fold upwards.

They form a tube. The tube FULLY closes around Day 28

The neural tube essentually becomes the CNS

The neural plate is the mesencymal cells on the edges that branch off once tube forms to become PNS

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7
Q

Explain what the development looks like at Day 18

A

Notochord signaling neural plate to start to fold

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8
Q

Explain what it looks like by Day 20

A

Day 20:

remarkable growth of the neural plate

Neural groove exists now (invagination of neural plate)

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9
Q

By Day 22.

explain what it looks like

A

By Day 22

Most of the neural tube is closed but not in two important areas

Not closed in the anterior neuropore area

and not closed in posterior neurophore area

By Day 22, the neural crest cells start to migrate to become Schwann cells, meninges, adrenal medulla, etc

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10
Q

By Day 25

what has happened now?

If that doesn’t happen what is the neural tube defects associated with it

A

Day 25:

The anterior neurophore closes

Also, there is development of the forebrain (prosencephalong), the midbrain (mesencephalon), and the hindbrain (rhombencephalon)

If the anterior neurophore does not close, RARE defect called ancephaly, where part of the brain and spinal chord are missing: FATAL

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11
Q

By Day 25, the anterior neurophore is closed

and the following primary vesicles have been developed

Forebrain

Midbrain

Hindbrain

Give them their “cephalon” names and also explain what secondary vesicles they develop into

A

Forebrain (prosencephalon): develops into telencephalon and diencephalon

Midbrain (mesencephalon): develops into mesencephalon

Hindbrain (rhombencephalon): develops into metencephalon and myelencephalon

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12
Q

Draw out the table

That shows the primary vesicles

Which secondary vesicles they develop into

Which mature brain regions those develop into

And then the ventricles associated with them

IMPORTANT TO KNOW THIS

A
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13
Q

The forebrain, also known as the __________cephalon

Develops into the _______ and the ________

Which develop into which brain regions

Associated with which ventricles?

A

Forebrain (prosencephalon)

Develops into the

  1. Telencephalon : becomes the cerebral cortex, the basal gangli, and the amgydala (ventricles are the lateral foramen of monro)
  2. Diencephalon: becomes the thalamus, hypothalamus, the pituitary and pineal glands (associated with the 3rd ventricle)
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14
Q

The midbrain, also known as the ______cephalon

Develops into what secondary vesicle

Associated with what brain region

Which ventricle

A

Midbrain (mesencephalon)

Stays as the mesencephalon

Mature brain region: midbrain

Ventricle: cerebral aqueduct

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15
Q

The hindbrain, known as the _______cephalon

Develops into which secondary vesicles

Which develop into which regions of the brain

associated with which ventricle

A

Hindbrain (rhombencephalon)

Develops into:

  1. metencephalon (pons and cerebellum)…… 4th ventricle
  2. myelencephalon, develops into medulla
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16
Q

By Day 27, what happens?

If it doesn’t what birth defect occurs?

A

Day 27: the posterior neurophore closes

If this doesn’t happen, concequence is SPINA BIFIDA

17
Q

Neural Tube Defects:

Most common _______

Attributed often to _______ acid

It is either a ______ defeciency or drugs that preven/inhibit the formation of it

(what are the drugs that cause that?)

A

Neural Tube Defects:

Most common birth defect

Often attributed to folic acid

Either defeciency in folic acid or drugs that prevent/inhibit the formation of it

Drugs: carbamezepine, phenytonin (for seizures), trimethoprim

18
Q

What are the three drugs that mess with folic acid

A

Drugs that mess with folic acid:

Carbamazepine

Phenytonin

Trimethoprim

19
Q

Explain Spina bifida occulta:

what is not closed?

A

Spina bifida occulta:

Very common

often asymptomatic or minor sensorimotor impairment

Neural tube may be closed but vertebral arch IS NOT CLOSED

tuft of hair is common

20
Q

What is the most severe kind of spina bifida

A

Most severe kind of spina bifida:

SBc with myeloschisis

open spinal chord

21
Q

Neural crest cells migrate during weeks _______ of gestation and give rise to what?

A

Neural crest cells migrate during weeks 4-7 of gestation and give rise to:

PNS (ganglia, enteric NS, schawann cells)

Meninges, adrenal medulla

melanocytes

22
Q

Explain growth factors that determine glial lineage

________ drives the self-renewal of progenitor cells

Exposure to ______ turns the progenitor cells into an astrocyte

A

PDGF drives self renewl of progenitor cell

CNTF turns it into an astrocyte

If the progenitor cell does not get exposed to CNTF, it becomes an oligodendrocyte

23
Q

Explain the “neurotrophin dependent pruning of neuronal connections”

A

So you have a bunch of neurons approaching a target cell

That target cells releases a finite amount of neurotrophin (growth factor)

The neurons that interact with that growth factor grow and reach the target, but the ones that do not get pruned/degenerate

24
Q

Remember the 3 vescicles did not include the spinal chord

A
25
Q

What is the most mild type of spina bifida

Most severe type of spina bifida

A

Most mild type of spina bifida: “occulta”

Most severe: myeloschisis (exposed spinal cord)