Test 2 - Textbook Notes for Chapters 5-7 Excellent textbook notes including all definitions in bold. ~30 pages of Word notes, nicely spaced and organized. *Notes taken from textbook called "Infants and Children" by Laura E. Berk - applies to the 6th a

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Published on 16 Oct 2011
School
University of Waterloo
Department
Psychology
Course
PSYCH211
Professor
Chapter Notes – PSYCH 211
Chapter 5
Body Growth
In the first 2 years bodies change at a faster rate than at any other time after
birth.
Changes in Body Size and Muscle-fat make-up
By end of first year, more than 50% higher fat than at birth. By 2 years, its
75% greater.
In one study, children were observed for 21 months and went for periods of 7-
63 days without growth before randomly adding as much as half an inch in a
24-hour period. Parents reported their babies hungry and irritant before the
day before this event occurred.
Muscle tissue increases slowly during infancy and will not reach a peak until
adolescence.
In infancy, girls are slightly shorter and lighter than boys with a higher fat to
muscle ratio. These differences persist and are magnified during adolescence.
Ethnic differences also exist for body/size/weight norms.
Changes in body proportions
Different parts of the body grow at difference rates.
Cephalocaudal trend: Latin for head to tail. During the prenatal period. The
head develops more rapidly than the lower part of the body.
Proximodistal trend: growth proceeds literally from near to far. From the
centre of the body outwards in the prenatal period the head, chest and trunk
grow first, then the arms and legs; and finally the feet and hands.
Skeletal Growth
Larger doesn’t necessarily mean more physically mature.
General Skeletal growth
The best estimate of a child’s physical maturity is skeletal age: which is a
measure of development of the bones of the body
The embryonic skeleton is first formed out of soft, pliable cartilage. In the 6th
week of pregnancy, the cartilage begins to harden into bone (a gradual
process that continues throughout childhood and adolescence).
Just before birth, special growth centres, epiphyses, appear at the 2 extreme
ends of each of the long bones of the body.
Cartilage cells continue to be produced at the growth plates of these
epiphyses, which increase in number throughout childhood and then as
growth continues, get thinner and disappear. After that no further growth in
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bone length is possible.
Girls are more advanced as maturing of skeletal age as well as of organs. This
allows girls to be less prone to environmental harmful influences. Girls have
lower developmental problems and child mortality rates.
Growth of skull
At birth, the bones of the skull are separated by 6 gaps or “soft plates” called
fontanels. Gaps allow overlapping as head passes through narrow birth
canal.
As skull bones come into contact with one another, they form “sutures” or
seams. Sutures disappear completely in adolescence when skull growth
ceases.
Brain Development
Development of neurons
There are 100-200 billion neurons that store and transmit information (unlike
ther cells, neurons aren’t tightly packed together). Between these neurons
are tiny gaps, or synapses, where fibres from different neurons come close
together but do not touch.
Neurons send messages by releasing a chemical, neurotransmitters, which
cross the synapse.
In prenatal period, neurons produced in embryo’s primitive neural tube, then
migrate to other body parts. Once in place, they differentiate to establish
purpose and connections.
Since neurons require space, a surprising aspect of brain growth is that as
synapses form, many surrounding neurons die (20-80% depending on brain
region). During prenatal period, neural tube produces far more neurons then
brain will ever need.
Neurons are stimulated by environment and from net-like connections.
At first stimulation results in massive over-abundance of synapses (many of
which are serving the same functions) thereby ensuring the child will acquire
the motor, cognitive, and social skills needed.
Synaptic pruning: a process where neurons that are seldom stimulated lose
their synapse. This returns neurons not needed at the moment to an
uncommitted state so they can support future development (about 40% of
synapses pruned during childhood and adolescence).
About half of the brain’s volume is due to glial cells which are responsible
for myelination (coating of neuron fibres with insulating fatty sheath-
myelin) which improves efficiency of message transfer.
Glial cells multiply rapidly in prenatal and into second year of life, and them
slows.
Brain development can be compared to “moulding a living sculpture”. After
neurons and synapses are overproduced, cell death and synaptic pruning
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sculpt away excess building material in order to form mature brain (also
influenced genetically and environmentally).
Neurophysiological Methods
Methods that detect changes in electrical activity of cerebral cortex.
oEEG (dynamics of brain-wave patterns)
oERP (location of brain-wave activity)
Neuroimaging techniques yield pictures of the brain (both require stillness so
not good for kids).
oPET (X-ray Photography)
ofMRI (Injection of radioactive substances)
Technique best used for kids, infants, and babies is NIRS: Near Infrared
Spectroscopy, in which infrared is beamed at regions of the cerebral cortex to
measure blood flow and oxygen metabolism while the child attends a
stimulus.
NIRS is limited to cerebral cortex
Sometimes not reliable and needs to be combined with other methods.
Development of the Cerebral Cortex
Cerebral Cortex: surrounds the rest of the brain and resembles half of a
shelled walnut. Largest structure accounting for 85% of brain’s weight and
containing the greatest number of neurons and synapses.
Regions of the Cortex
The order in which cortical regions develop correspond to the order in which
various capacities emerge in the infant and growing child (ex. Burst in
auditory and visual areas and mastery of motor skills in 1st year. Language
active from late infancy to early childhood).
Frontal lobes have most extended period of development.
Prefrontal Cortex: Responsible for thought (consciousness, inhibition of
impulses, integration of information, use of memory, planning, reason,
problem solving).
Lateralization and Plasticity of the Cerebral Cortex
Contra-lateral with the exception of the eyes (messages of right half of each
retina goes to right side of brain).
Left= verbal abilities (spoken and written) and positive emotion.
Right= spatial abilities: judging distances, reading maps, and negative
emotions.
In left handers, this pattern may be reversed or not as lateralized.
Left is better at processing info piece by piece, while right is better at
processing info by looking at the whole picture (holistically).
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Document Summary

In the first 2 years bodies change at a faster rate than at any other time after birth. Changes in body size and muscle-fat make-up: by end of first year, more than 50% higher fat than at birth. In one study, children were observed for 21 months and went for periods of 7- 63 days without growth before randomly adding as much as half an inch in a. Parents reported their babies hungry and irritant before the day before this event occurred: muscle tissue increases slowly during infancy and will not reach a peak until adolescence. In infancy, girls are slightly shorter and lighter than boys with a higher fat to muscle ratio. These differences persist and are magnified during adolescence: ethnic differences also exist for body/size/weight norms. Changes in body proportions: different parts of the body grow at difference rates, cephalocaudal trend: latin for head to tail.

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