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Transcript
Psychology 304:
Brain and Behaviour
Lecture 17
1
Development of the Nervous System
1. What are the phases of prenatal neurodevelopment?
2
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.
3
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.
4
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.
5
Formation of Neural Tube
6
Electron Micrograph of Neural Tube Closure
7
Electron Micrograph of Neural Tube Closure
8
Neural Tube
9
Embryonic Neural Tube Development
10
 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.
11
Forebrain
Midbrain
Hindbrain
Spinal cord
CNS Development from the Neural Tube
12
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.
13
Directions of Migration
14
 Cells migrate via two processes: somal translocation
and glia-mediated migration.
 Cell migration is guided be cell-adhesion molecules.
15
Processes of Migration
16
Glial-Mediated Migration
17
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.
18
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.
19
Growth Cone with Filopodia
20
Filopodia and Lammelipodia
21
Development of the Nervous System
1. What are the phases of prenatal neurodevelopment?
22