Unit 1 Psychology
Area of Study 1: How does the brain function?
Key knowledge: Dot point 6
“Infancy and adolescence as periods of rapid development and changes in brain structure
and function, including development of myelin, synaptic pruning and frontal lobe
development.”
The developing brain
Infancy and adolescence are the two stages of life where we experience the most rapid changes to
our brain.
Infancy is the first two years of life and Adolescence is the onset of puberty, usually between the
ages of 12-18.
By the age of 3, the brain is three quarters the size of the adult brain.
By the end of puberty (adulthood), the brain is composed of more than 100 billion neurons with
approximately 60 trillion neural connections.
The development of the brain, and the nervous system, begins before birth. This process is known as
‘Developmental Plasticity,’ and there are five stages.
Developmental Plasticity: the ability of synapses to be modified.
Developmental plasticity occurs before birth and through the early period of life and involves the
development of the nervous system.
Development of the nervous system goes through five stages:
1.
2.
3.
4.
5.
Proliferation
Migration
Circuit formation
Circuit pruning
Myelination
A little memory trick to remember the stages:
Pac Man Can’t Catch Me
Pac = Proliferation
Man = Migration
Can’t = Circuit formation
Catch = Circuit pruning
Me = Myelination
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Proliferation: unborn baby’s cells that will be neurons divide and multiply. Up to 250,000 cells per
minute.
Migration: newly formed neurons move to their destined location. The role of a neuron is
determined by where it is located when it is formed.
Circuit (synaptic) formation: axons of new neurons grow out to target cells and form synapses with
them.
The more neural pathways are used the stronger the synaptic connections become, strengthening
and speeding up the neural pathway (neurons that fire together, wire together). This fits in with the
old saying, “Practice makes perfect.”
Circuit (synaptic) pruning: elimination of excess neurons and synapses. Pruning occurs during
infancy and childhood, but there is a second wave of pruning in early adolescence. Neurons that
don’t ‘fire’ together get pruned.
Myelination: axons in the child’s brain become covered in myelin. This coating insulates the axon
and prevents electrical interference from other neurons. It also speeds up the rate of transmission of
signals within the neuron and prevents the neural impulse from leaving the axon before it reaches
the axon terminals.
Myelination starts at the lower structures of the brain, before progressing to the cerebral
hemispheres from the occipital lobe to the temporal and parietal lobe and then finally the frontal
lobe. The left frontal lobe is the last area of the brain to undergo this process.
Myelination begins before birth and is not completed until the prefrontal cortex is fully developed in
early adulthood (the last part of the brain to develop).
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