Neuronal development and the brain

24 important questions on Neuronal development and the brain

What is the Piaget’s object permanence task?

An infant sees a toy and then an investigator places a barrier in front of the toy. Infants younger than about 9 months old fail to reach for the hidden toy. Tasks that require a response to a stimulus that is no longer present depend on the prefrontal cortex, a structure that is slow to mature.

When and how does the central nervous system begin to form?

When the embryo is 2 weeks old the dorsal surface thickens forming a neural tube surrounding a fluid filled cavity. The forward end enlarges and differentiates into the hindbrain, midbrain, and forebrain. The rest of the neural tube becomes the spinal cord.

How does the brain from three vesicles go to the five vesicle stage?

The forebrain becomes the telechephalon and diencephalon, the midbrain becomes the mesencephalon and the hindbrain becomes the metencephalon and myelencephalon.
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What is the difference between sulci, fissures, and gyri?

Sulci are minor grooves, fissures are deep grooves, gyri are rims (randen).

What is the function of glial cells (astrocytes and oligodendrocytes)? How do oligodendrocytes do this?

Glial cells are responsible for maintaining neurons and communication.
Oligodendrocytes produce myeline.

What are the 8 phases in embryonic and fetal brain development at a cellular level?

  1. Mitosis/Profileration
  2. Migration
  3. Differentiation
  4. Aggregation
  5. Synaptogenesis
  6. Neuron Death
  7. Synapse Rearrangement
  8. Myelination

What does the neuroepithelial layer give rise to?

The neuroepithelial layer gives rise to neuroblasts.

Explain the difference between symmetric and asymmetric division using neuroepithelial of the neural tube.

The stem cells in the neuroepithelia can divide into two new stem cells or two committed cells, this is called symmetric cell division.
The stem cells can also divide into one stem cell and one committed cell, this is called asymmetric division.

What happens during the first step of brain development, mitosis/proliferation?

At early stages, a stem cell generates neuroblasts. Later, it undergoes a specific asymmetric division (the “switch point”) at which it changes from making neurons to making glia

Where does the first step of brain development, mitosis/proliferation take place?

In the ventricular zone.

What happens during the second step of brain development, migration?

The neurons 'migrate' to the spot where they have to be.

How do neurons know where to migrate to?

Radial glia are made that reach out towards the cortical plate making kind of a ladder type so the neurons can go up.
Also neurons have growth cones that sense the right cues to grow into the right direction.

What is the order of radial glia and neurons?

Radial glia are made first, later neurons grab the radial glia to end up on the outside of the brain (cortical plate).

What happens during the third step of brain development, differentiation?

Neurons become fixed post mitotic and specialized, they develop processes (axons and dendrites), and they develop neurotransmitter-making ability.

How do neurons know what to become?

Neurons differentiate according to their cell fate which is determined by their position in the gradient.

What can you say about the BMP concentrations where pyramidal neurons and astrocytes are formed?

Pyramidal neurons and astrocytes are formed in regions with a high BMP concentration.

What is the advantage of myeline around neurons?

Neurons surrounded by myeline have a better conductance.

What happens during the fourth phase of brain development, aggregation?

During aggregation the neurons form organized layers.

What happens during the fifth phase of brain development, synaptogenesis?

Axons (with growth cones on end) form a synapse with other neurons or tissue (muscle).

Explain the difference between axo-dendritic, axo-somatic, and axo-axonic.

Axo-dendritic means that an axon is connected to a dendrite of another neuron.
Axo-somatic means that an axon is connected to the body of another neuron.
Axo-axonic means that an axon is connected to an axon of another neuron.

What is important in knowing where to go, for neurons but also for synapses?

Repellant and attractant substances.

Why do during the sixth phase of brain development neurons die?

The neurons that die during this phase fail to make optimal synapses.

What happens during the seventh phase of brain development, synapse rearrangement?

Active synapses likely take up neurotrophic factor that maintains the synapse. Inactive synapses get too little trophic factor to remain stable.
In the end this causes one single nerve cell to be innervating with a single muscle cells.

What happens during the eight phase of brain development, myelination? Why is this necessary?

During this phase the process whereby glial cells wrap themselves around axons happens. This increases the speed of neural conduction.

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