Download Fourth week

Fourth week
• By the fourth week, part of
the neural plate has folded
in on itself to form a neural
tube.
• Part of this eventually
becomes the spinal cord and
ventricles in the brain These
‘hollow’ areas contain fluid.
• At this point, primitive brain
cells called neuroepithelial
cells begin to divide rapidly,
or proliferate.
About 4 weeks of age
• Three bulges emerge from the top of the neural tube,
eventually giving rise to the forebrain midbrain, and
hindbrain. We will talk about these three areas in a
minute. The rest of the neural plate becomes the neural
crest, which will become the spinal cord.
Synapse formation
• Known as synaptogenisisappears dependent upon glial
cells
• Likely any given synapse is
under a series of chemical
signals in which each pre and
postsynaptic neuron weighs a
variety of synaptic-promoting
and synaptic inhibiting signals
before forming synapses with
the best available cells
Back to the structures in the growing brain 2nd and 3rd month
• The growing brain is beginning
to take shape.
• The hindbrain gives rise to the
medulla oblongata and the
pons (part of the brain stem),
which are involved in many
functions essential to life, such
as breathing and heartbeat.
• The cerebellum, the part of the
brain involved in maintaining
balance and coordinating
movement, emerges partly
from the hindbrain and partly
from the midbrain.
2nd and 3rd month- Forebrain
development- diencephalon
It is the forebrain that
undergoes the most
complicated changes.
• The forebrain divides into
two distinct structures: the
diencephalon and
telencephalon.
• The diencephalon develops
into the thalamus and
hypothalamus, which will
affect everything from
emotions to sensory
perception.
2nd and 3rd month- Forebrain
development- telencephalon
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The telencephalon gives rise to
several parts.
First comes the hippocampus,
which eventually will be involved
in short-term memory, and other
structures involved in the olfactory
pathways
Next, the telencephalon produces
the basal ganglia, which will
eventually contain structures that
control movement, sensory
information, and some types of
learning.
The amygdala will eventually help
the brain attach emotional
significance to signals it relays
elsewhere.
Late Pregnancy Nervous system
developments
• During the last phase of development, the earlier
processes of cell proliferation and migration continue
to some degree, and synapses continue to form all
over the brain.
• But two new processes begin in earnest: a pruning of
unnecessary cells and connections - an active
process, known as apoptosis, or programmed cell
death (as contrasted to necrosis which is a passive
process) , and the protection, known as myelination,
of vulnerable neurons and connections.