Ch15 - Module 1

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?

1. Gene duplication

2. 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?

1. Genetics

2. Experience

3. 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)