Lecture 10 Nervous System Development I Flashcards
5 events during development
“Gina Introduced Ny’s Finest Veteran”
Gastrulation
Induction
Neurulation
Fusion (neurulation ends)
Vesicle formation
As totipotent stem cells divide….
They will have more specialised function and their plasticity/renewal decreases.
Gastrulation
- What is it?
- Process of proliferation of epiblast cells (innercell mass)
- Migration of cells to different regions.
- When specialisation starts.
- Blastula -> gastrula (organisation of cells into the three layers)
Gastrulation
- What are the three layers formed from it and what do these layers develop into
Endoderm (lining of internal organs - gastrointestinal, respiratory, endocrine)
Mesoderm [MC] (muscles, connective tissue)
- notochord, somites (spinal vertebrae)
Ectoderm [BS] (brain, skin)
- neural plate
Induction
- What
- How does it occur?
- How different tissue types form
Development of different tissues and layers due to influence from other tissues contributed by neurochemicals.
- Through secreted growth factors .
induction
What are the main growth factors of neural induction for developing the nervous system?
BMP4, chordin, noggin, FGF
induction
Describe the functions of these growth factors : BMP4, chordin & noggin (inhibitors), FGF
Poles, AB, PS
BMP4 - induce polarity in embryo (so cells know whether to become brain cells or spinal cord cells ), inhibited when neuroectoderm forms, induce ectoderm to become epidermal skin
BMP4, Chordin & Noggin - inhibits BMP4 -> anterior neuroectoderm forms which will become the brain
BMP4 & FGF - posteriors neuroectoderm form -> spinal cord
What does the notochord do
Induce BMP4 in ectoderm, influencing neural plate folding
Describe neural plate folding to form the neural tube
(Neurulation + fusion)
Notochord releases BMP4 to trigger neural folding.
The ectoderm folds inwards at the neural plate forming the neural groove.
As neural plate folds, the neural folds on either side of the neural groove will eventually fuse starting from the middle towards the rostral and caudal ends, forming the neural tube.
The tube closes properly and disconnects from the rest of the ectoderm.
Now, true polarity.
Neural crests cells develop from the neural tube and they go on to form a variety of cells
What are they known as?
What kind of cells do they go on to form that will be part of the nervous system?
Fourth type of germ layer
Neurons and glia of cranial ganglia
Sensory neurons and glia of periphery
Neural crest
Neural tube
Somites
Develops into…..
Peripheral nervous system (PNS)
Central nervous system (CNS)
Spinal vertebrae
Neural tube birth defects (failure to close in the…) and consequences
-anterior neural pole
-posterior neural pole
- anencephaly - brain no develop properly (no cortex) -> spontaneous abortion, still birth, baby live for little while after birth
- (A) spina bifida sistica - back of spinal cord don’t close forming a sack with fluid build up -> fixed surgically
(B) spina bifida occulta - unseen, issue noticeable if back injury and detected by xray, failure to close, no fluid buildup -> treat easily by diet with folate - spine growth & fill gap
When does the neural tube usually close
Between week 4 - week 12
Vesicle formation
State the vesicle formation stage and what week they normally occur
Three vesicle stage - Week 4
Five vesicle stage - Week 6
State the three vesicles that form at the three vesicle stages and what they will go on to form
Prosencephalon -> forebrain
Mesencephalon -> midbrain
Rhombencephalon -> hindbrain
