Singh 1: Development of the Nervous System Flashcards
Key Concepts in Early Development:
Initially all neural cells are ______ but all end up having ______
Initially, all neural cells are equivalent but all end up having unique identities.
Key concepts in early development:
Regionalization and specificity arise due to ______________
Regionalization arises ____ and dictates ____
Regionalization and specificity arise due to differential exposure to gradients of signaling molecules (space/time)
Regionalization arises early and dictates identity and adult function
Key concepts in early development:
The CNS develops from a ______ of cells that ______ into a tube
The tube _____, _____ and _____
Some parts of the tube ______
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
Major events in early nervous system development:
What happens by 3-4 weeks?
What happens by 6 weeks?
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
What are the three germinal layers that form the embryonic disc?
What does each develop into?
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)
Explain via diagram how the neural plate becomes a tube
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
Explain what the development looks like at Day 18
Notochord signaling neural plate to start to fold
Explain what it looks like by Day 20
Day 20:
remarkable growth of the neural plate
Neural groove exists now (invagination of neural plate)
By Day 22.
explain what it looks like
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
By Day 25
what has happened now?
If that doesn’t happen what is the neural tube defects associated with it
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
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
Forebrain (prosencephalon): develops into telencephalon and diencephalon
Midbrain (mesencephalon): develops into mesencephalon
Hindbrain (rhombencephalon): develops into metencephalon and myelencephalon
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
The forebrain, also known as the __________cephalon
Develops into the _______ and the ________
Which develop into which brain regions
Associated with which ventricles?
Forebrain (prosencephalon)
Develops into the
- Telencephalon : becomes the cerebral cortex, the basal gangli, and the amgydala (ventricles are the lateral foramen of monro)
- Diencephalon: becomes the thalamus, hypothalamus, the pituitary and pineal glands (associated with the 3rd ventricle)
The midbrain, also known as the ______cephalon
Develops into what secondary vesicle
Associated with what brain region
Which ventricle
Midbrain (mesencephalon)
Stays as the mesencephalon
Mature brain region: midbrain
Ventricle: cerebral aqueduct
The hindbrain, known as the _______cephalon
Develops into which secondary vesicles
Which develop into which regions of the brain
associated with which ventricle
Hindbrain (rhombencephalon)
Develops into:
- metencephalon (pons and cerebellum)…… 4th ventricle
- myelencephalon, develops into medulla
By Day 27, what happens?
If it doesn’t what birth defect occurs?
Day 27: the posterior neurophore closes
If this doesn’t happen, concequence is SPINA BIFIDA
Explain Spina bifida occulta:
what is not closed?
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
Explain growth factors that determine glial lineage
________ drives the self-renewal of progenitor cells
Exposure to ______ turns the progenitor cells into an astrocyte
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
Explain the “neurotrophin dependent pruning of neuronal connections”
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
