Chapter 5 – The Childs Growth: Brain, Body and Sexual Maturation
Brain development in Infancy
at birth the babies brain weighs 1/4 of the mature brain, 6m increases to ½ and 2
year olds weighs 75 percent.
Cerebrum: 2 connected hemipheres. Speech and awareness, sensory perception,
motor abilities and memory.
Cerebral cortex: 90% of brains cell bodies. The covering layer of the cerebrum.
Seeing, hearing, moving, feeling emotions, thinking and speaking can be traced to
(figure 51, figure 52, pg 157).
Neurons and synapses
Neurons: cell in bodies nerous system. Consists of cell body, long projection
(axon) and several shorter projections called dendrites. They send and receive
neural impulses (messages) through the brain and nervous system. Baby is born
with almost full amount. Studies suggest that adult brain can regenerate nerve
Neuron proliferation: during embryotic period neurons multiply at a rapid pace.
250, 000 neurons born every minute.
Glial cells: a nerve cell that surrounds and protects neurons and creates myelin
(fatty membrane) sheaths to cover them. They regulate the nutrients, and repair
Myelination norm occurs during the first 2 years but can also cont. after that into
adulthood. Facilitates transfer of signal rapidly and efficiently.
Neural migration: movement of neurons within the brain to ensure that all areas
have a sufficient # of neural connections. If there is not a sufficient amount it is
associated with mental disabilities and disorders(dyslexia, schizophrenia).
Synapse: a specialized site of intercellular communication where info is
exchanged between nerve cells, usually by means of neurotransmitter.
Synaptogenesis: forming of synapses, begins prenatally. By 2y old there are
roughly 15000 synapses for every neuron.
Neuronal death: death of some neurons that surround newly formed synaptic
connections among other neurons.
Synaptic pruning: brains disposal of the axon and dendrites that are not often
stimulated. This frees space for other synaptic connections.
Adulthood: about 1 trillion neurons, 100 to 100 connections with other neurons,
(figure 53, figure 54, pg 158), (figure 55, pg 159) (turning points, pg 160
161). (Figure 56, pg 162).
Sequential Development of the Brain
when baby moves from involuntary reflex to voluntary control the motor are aof
the brain develops rapidly.
Visual cortex synapses per neuron is multiplied 6 times within first 2 years. Visual
experience is greatly enhanced. Hemispheric specialization
Hemisphere: 2 halfs of the cerebrum
Corpus callosum: the band of nerve fibres that connect the hemispheres. The two
halves have cross wiring between them which means that for most functions it
involves both parts of the brain. When one side suffers damage the other side may
be able to take over those functions.
Left and right brain functions
hemispheric specialization: differential functioning of the 2 hemispheres. (e.g.
language by left and visual special by right).
Left moves right, right moves left.
Lateralization: process which each half of the brain becomes specialized for
performance of certain functions.
Right hem.: visual special, non speech sounds, perception of faces and emotional
Left hemisphere associated with approach to external environment and the right
hemisphere will cause person to turn away and run or withdraw.
Ppl who are deaf have their right hemisphere take over language when using sign.
If damage occurs in the early years before hem. Specialization is complete the
younger kid will gain back their losses. Adults need treatment to try to recover.
Consequences of brain lateralization
infants whos left hem. Differentiates among speech sounds and the right hem for
non speech sounds have better language skills at age 3.
Dyslexia: difficulties in reading or learning to read. Difficulty integrating visual
and auditory info, matching written words to sounds and letters to words. Some
confuse letters and others cant break up letters and syllables treating the word as a
Some researchers thing that the brain of dyslexic individuals did not lateralize
properly leading to an overlaod in the left hem., causing deficits in language
skills. (e.g. reading).
Handedness is laterized. 90% right handed. Some left handed ppl are
ambidextrous (able to use both hands) which suggests that their brains are less
The brains plasticity: experience and brain development
plasticity: the capacity of the brain, particularily in its developmental stages, to
respond and adapt to input from the external environment.
Two types of experiences influence brain dev. (1)stimulation from touch,
patterned visual input, sounds of language, affectionate expressions from
caregivers and nutrition. Which brings out normal brain dev. When there is
interference the ability is impaired (e.g. cataracts, cause impairment in vision
dev.). (2) experiences that are unique to the individual. (e.g. within family or
culture). (e.g. children in Mozambique develop motor cortex to gain skill in
hunting. Adult brains can undergo structural change through unique experience.
Lack of stimulation, exposure to traumatic events can damage the brain or cause it
to malfunction. In abused children the limbic and cortex (involvedin emotion and
child parent relationship) are smaller and have fewer synapses.
(table 51, pg 167), (figure 58, pg 167). Techniques for studying human brain
function and structure/ how early deprivation can affect brain activity.
Reaching out and grasping: newborns grasping reflex and preaching
(uncoordinated swipes), 3 months directed reaching, 5 months reach in for an
object and actually grasp it. It involves: muscle growth, portsural control, control
over arms and hands, and a variety of perceptual and motor abilities. Dynamic
systems: only when everything is achieved can the baby reach out and grasp an
By proving a visually stimulating environment o a baby it can advance their
ability to attend to object and reach for them. Experience.
Gripping. Smaller objects they use index finger and thumb, larger objects they use
all fingers or both hands. 4m use touch to determine grip, 8m use vision (preshape
By age 2 they can use hands skilfully in play
Stepping reflex appears when born and disappears at 2m. by the second half of the
first year a voluntary stepping motion appears. 1 year infants begin to walk
Maturational theorists: say its development of the motor cortex.
Cognitive theorists: cognitive plan or consequences of watching others as well as
the practice of actually stepping.
Dynamic: walking skills are determined by an interplay of a variety of emotional,
perceptual, attentional, motivational, postural, and anatomical factors.
7 year olds have acquired running, galloping, hoping.
How locomotion may affect other aspects of development
when locomotor dev, is achieved the baby is able to become more independent
and explore their own environment, and initiate more contact with ppl.
Perceptionaction coupling approach: locomotion can change the ways babies
perceive the world. (e.g. crawling brings out fear of heights and other special
abilities. They are better able at understanding special orientation (e.g. crawling
infants can better find an object hidden in a room). The moving room is also
another example. The baby uses visual input from the moving room to control
their balance. 36 year olds will sway with the room.
The role of experience and culture when babies are given more special attention (e.g. massage, exercise, practice) the
baby achives more motor milestones sooner.
Zambia mothers carry babies in a sling and let the sit alone which allows them to
practice motor skills, jamacian mothers massage their babies, stretch and practice
stepping, Mexican are tightly swaddledfor the first 3 months so they have less
advanced motor skills, chinese put them on feather beds and pillows to prevent
from injury so babies crawling si restricted.
(figure 59, pg 171).
Seasons can affect the motor development. It is a lot easier in summer than in
winter. (e.g. learning to walk with a snowsuit on is difficult). **constraints from
(box 5.1 risk and resilience blindness, motor development and cognitive
Cephalocaudal development: human physical growth occurs from the head
Proximaldistal pattern: physical development to occur from the center outwards.
Babies double their weight in the first 3 months, and triple their weight by the
end of the first year.
Shape: newborns are top heavy, they then gain more weight and become more
cylinder shaped. Then become slender kindergardeners.
Growth is episodic.
(figure 511, pg 174).
Do genes affect height and weight?
there is an interplay between the environment and genes, however genes highly
determine ohsycial traits. Supported by adoption and twin studies.
Girls tend to be taller than boy from age 29. Boys then catch up. At around 10 ½
girls have a growth spurt and at age 14 girls height plateaus. Boys continue to
grow until 18. It is a sim. Pattern for weight.
Girls tend to be lighter at birth, then gain more weight than boys until 14.
Tanner coined the term tempo of growth: variability in tiing of changes in
The influence of Environmental Factors
(e.g. nutrition, psychological disorders, climate, home environment, etc.). in
favourable environment childrens growth will look similar to one another.