Transcript What are the phases of prenatal neurodevelopment?

Psychology 304:
Brain and Behaviour
Lecture 17
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Development of the Nervous System
1. What are the phases of prenatal neurodevelopment?
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Announcements
1. This morning, Naghmeh informed me that she made an
error in scoring the labels for version 2 of the exam. She
is in the process of correcting the scores. I will post the
revised grades on the course website as soon as they are
available.
2. Students who are absent from class and/or exams due
to illness are now required by the University to indicate
their absence using the online reporting system
available through the Student Service Centre.
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3. As a consequence of my absence due to illness, we
will not be able to discuss chapter 11 (Motor Control
and Plasticity) in class. As a result, this chapter will
not be included on the final exam.
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What are the phases of prenatal neurodevelopment?
• Prenatal neurodevelopment is marked by a number of
discrete phases:
1. Development of the neural plate and neurogenesis.
 Within 3 weeks of conception, the embryo shows
three cell layers: The ectoderm, mesoderm, and
endoderm. The nervous system develops from the
ectoderm, often referred to as the neural plate.
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Formation of Neural Tube
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Electron Micrograph of Neural Tube Closure
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Electron Micrograph of Neural Tube Closure
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Neural Tube
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Embryonic Neural Tube Development
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 Once formed, the cells that line the inner surface of
the neural tube—that is, the ventricular zone—divide
and proliferate.
 The anterior end of the neural tube ultimately
develops into the forebrain, midbrain, and hindbrain.
 The posterior end of the neural tube ultimately
develops into the cerebral ventricles and central canal
of the spinal cord.
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Forebrain
Midbrain
Hindbrain
Spinal cord
CNS Development from the Neural Tube
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2. Cell migration
 Once cells have developed in the ventricular zone,
they migrate to target locations.
 Migration occurs in two directions: radial migration
and tangential migration.
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Directions of Migration
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 Cells migrate via two processes: somal translocation
and glia-mediated migration.
 Cell migration is guided be cell-adhesion molecules.
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Processes of Migration
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Glial-Mediated Migration
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3. Cell differentiation
 Once cells have reached their target locations, they
differentiate into region-specific neurons and glial
cells.
 Cell differentiation is determined by genetic programs
and cell-cell interactions.
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4. Axon growth and synaptogenesis
 Once cells have differentiated into region-specific
neurons, axons and dendrites begin to grow from
them.
 Axonal and dendritic growth are directed at
appropriate targets.
 Filopodia and lamellipodia extend and retract from
growth cones, in search of appropriate targets.
 Chemoattractants and chemorepellents guide
axonal growth.
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Growth Cone with Filopodia
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Filopodia and Lammelipodia
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Development of the Nervous System
1. What are the phases of prenatal neurodevelopment?
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