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The Developing Nervous System: Pre-Postnatdevelopment
When does development of the human nervous system begin?
around the 18th day after conception
What is the sequential development of the nervous system?
Ectoderm (outer embryo layer) → Neural Tube → Ganglia of the autonomic nervous system
When does the neural tube close?
By the 28th day
What three chambers are formed by the closing of the neural tube?
forebrain
midbrain
hindbrain
What structures develop the hindbrain?
the metencephalon (afterbrain) and myelencephalon (marrowbrain)
The region surrounding the lateral ventricles becomes the ______________
telencephalon
The region around the third ventricle becomes the _________________
diencephalon
How much does the neural tube weigh?
3lbs (ie) 1400g
How thick is the cerebral cortex?
Approximately 3mm
What does the cerebral cortex surround?
The cerebral hemispheres
True or False:
“The cerebral cortex is larger in humans than any other species”
True
______ cells that line the inside of the neural tube give rise to the cells of the CNS
stem
The cebral cortex develops from the ______
inside out
There are _____ layers of the cerebral cortex
six
The stem cells that give rise to the cells of the brain are known as ______
progenitor cells
What is symmetrical division?
the movement of progenitor cells from the ventricular zone to the subventricular zone
When does asymmeticral division begin?
7 weeks after conception
What is asymmetrical division? How long does it last?
the division of the progenitor cell into another progenitor cell and a brain cell; 3 months
The first brain cells produced through asymmetrical division are _______
radial glia; they extend fibres outward of the VZ like spokes in a wheel
How many neurons migrate along radial glial fibres on any given day?
1 billion
What neurons migrate the shortest?
early neurons migrate in a day
How long do the outermost layer neurons take to migrate?
2 weeks
What is apoptosis?
A chemically induced “falling away” signal that indicates the end of cortical development and turns radial glia into astrocytes
What is pruning?
the death of 50% of neurons via apoptosis; they do not receive the survival signal from the postsynaptic cell
Why is pruning necessary?
Evolutionarily, it was safer to over produce neurons and have them compete for conections than to try to produce the right amount
The ultimate size of the brain is determined by the size of the ________
ventricular zone
What types of genetic changes are requires to produce a larger complex brain?
Gene duplication
Delays in the termination of the symmetrical & asymmetrical divisions
The human brain is ____x larger than that of a Rhesus Macaque Monkey
10; due to symmetrical divisions lasting 2 days longer in humans
The human brain is ______% thicker than that of a Rhesus Macaque Monkey
15%; due to asymmetrical divisions
True or False:
“The cortex of a convoluted brain contains many more neurons that that of a smooth brain”
True
How long does the human brain continue to develop for after birth?
at least 2 decades
What factors control the pattern of postnatal development?
Genetics
Experience
Neurogenesis
Stereopsis is an example of how _____ affects brain development?
Experience
Stereopsis - a form of depth perception obtained from the experience of viewing with both eyes and it occurs between 1-3yrs of age
After the removal of a limb, one becomes _____ sensitive to touch in these regions after changes in the cortex occur
more
Musicians have a larger cortical region devoted to analysing sensory information from the fingers of their _____ hand
left
Blind persons have an enlargened region of the _______
cerebral cortex
In the adult brain, neurogenesis occurs in the _______ and the _______
hippocampus (learning)
the olfactory blulbs (smell)
Note 
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