Infancy: Physical Development Chapter 4 and 5 Infant development progresses rapidly. Infants usually come into this world equipped to begin the journey of life! 1 Principles of Development Cephalocaudal Proximodistal Cephalocaudal – refers to development as progressing from head to toe. Consider muscle development babies begin by being able to lift their head and then it progresses to ultimate control of muscles which would be walking. Proximodistal refers to center out. Again consider the last area one gains control is the fingers. 2 Skeletal Growth Skeletal Age Epiphyses Fontanels The best estimate of a child’s physical maturity is skeletal age, which is a measure of development of the bones of the body. Epiphyses are growth centers, that appear at the ends of the long end of the bones of the body. Cartilage cells continue to be produces at the growth plates of these epiphyses, which increase in number throughout childhood and then as growth continues, get thinner and disappear. Skull growth is especially rapid between birth and 2 years of age due to large increases in brain size. At birth the bones of the skull are separated by gaps called fontanels. These gaps help during the birth process and also allow for brain development. There are 6 of these – the largest is the anterior gap. It will gradually shrink and fill in during the second year. The other fontanels are smaller and close more quickly. As the skull bones come in contact with one another, they form sutures or seams, these permit the skull to expand easily as the brain grows. The sutures will disappear when skull growth is complete, during the teen years. 3 Brain Development Synaptic Pruning Myelination Cerebral Cortex Prefrontal cortex Hemispheres Lateralization Brain plasticity At birth the brain is nearer to its adult size than any other physical structure. Human brain has 100 to 200 billion neurons or nerve cells that store and transmit information. Between nuerons are tiny gaps or synapses, where fibers from different neurons come close together but do not touch. Neurons send messages to one another by releasing chemicals call neurotransmitters which cross the synapse. During infancy and toddlerhood, neural fibers and synapses increase dramatically. Because developing neurons require space for connective structures, as synapses form surrounding neurons will die. As neurons form connections, stimulation becomes vital for their survival. Neurons that are stimulated by input from the surrounding environment continue to establish new synapses, forming increasingly elaborate systems of communication that support more complex abilities. Neurons that are seldom stimulated soon lose their synapses, through synaptic pruning, which returns neurons not needed at the moment to an uncommitted state so they can support future development. About half of the brain is made up of glial cells which are responsible for myelination, the coating of.

1. Infancy: Physical Development
Chapter 4 and 5
Infant development progresses rapidly. Infants usually come
into this world equipped to begin the journey of life!
1
Principles of Development
Cephalocaudal
Proximodistal
Cephalocaudal – refers to development as progressing from
head to toe. Consider muscle development babies begin by
being able to lift their head and then it progresses to ultimate
control of muscles which would be walking.
Proximodistal refers to center out. Again consider the last area
one gains control is the fingers.
2
Skeletal Growth
Skeletal Age
Epiphyses

2. Fontanels
The best estimate of a child’s physical maturity is skeletal age,
which is a measure of development of the bones of the body.
Epiphyses are growth centers, that appear at the ends of the
long end of the bones of the body. Cartilage cells continue to
be produces at the growth plates of these epiphyses, which
increase in number throughout childhood and then as growth
continues, get thinner and disappear.
Skull growth is especially rapid between birth and 2 years of
age due to large increases in brain size. At birth the bones of
the skull are separated by gaps called fontanels. These gaps
help during the birth process and also allow for brain
development. There are 6 of these – the largest is the anterior
gap. It will gradually shrink and fill in during the second year.
The other fontanels are smaller and close more quickly. As the
skull bones come in contact with one another, they form sutures
or seams, these permit the skull to expand easily as the brain
grows. The sutures will disappear when skull growth is
complete, during the teen years.
3
Brain Development
Synaptic Pruning
Myelination
Cerebral Cortex
Prefrontal cortex
Hemispheres
Lateralization
Brain plasticity

3. At birth the brain is nearer to its adult size than any other
physical structure.
Human brain has 100 to 200 billion neurons or nerve cells that
store and transmit information. Between nuerons are tiny gaps
or synapses, where fibers from different neurons come close
together but do not touch. Neurons send messages to one
another by releasing chemicals call neurotransmitters which
cross the synapse. During infancy and toddlerhood, neural
fibers and synapses increase dramatically. Because developing
neurons require space for connective structures, as synapses
form surrounding neurons will die. As neurons form
connections, stimulation becomes vital for their survival.
Neurons that are stimulated by input from the surrounding
environment continue to establish new synapses, forming
increasingly elaborate systems of communication that support
more complex abilities. Neurons that are seldom stimulated
soon lose their synapses, through synaptic pruning, which
returns neurons not needed at the moment to an uncommitted
state so they can support future development.
About half of the brain is made up of glial cells which are
responsible for myelination, the coating of the neural fibers
with an insulating fatty sheath (myelin) that improves efficiency
of message transfer.
Cerebral Cortex – largest brain structure – accounting for 85%
of the brain’s weight and containing the greatest number of
neurons and synapses. It is the largest part of the brain to stop
growing; consequently is it sensitive to environmental
influences for a much longer period than any other part of the
brain. The order in which regions of the cortex develops
corresponds to the order in which various capacities emerge in
infancy as well as in other developmental periods. The region

4. with the most extend period of development are the frontal
lobes. The prefrontal cortex is responsible for thought (in
particular consciousness, inhibition of impulses, integration of
information and use of memory, reasoning, planning and
problem solving strategies).
The cerebral cortex has 2 hemispheres (sides) that differ in
functions. For example each hemisphere receives sensory
information from the side of the body opposite to it and controls
only that side. For most individuals, left controls verbal
abilities and positive emotion and right handles spatial abilities
and negative emotions. This specialization of function is also
called lateralization.
Brain plasticity –the brain is more plastic during the first few
years than it will ever be again. An overabundance of synaptic
connections supports brain plasticity. A highly plastic cerebral
cortex in which many areas are not yet committed to specific
functions, has a high capacity for learning. And if a part of the
cortex is damaged, other parts can take over the tasks it would
have handled. Please note the experience greatly influences the
rate and success of its organization.
4
Brain Development Continued
Experience-expectant brain growth
Experience-dependent brain growth
Experience-expectant brain growth – refers to the young brain’s
rapidly developing organization, which depends on ordinary
experiences – opportunities to see and touch objects, hear
language and other sounds, and to move about and explore the
environment. Young children’s brains seem to expect these!

5. Experience-dependent brain growth – occurs throughout our
lives and consists of additional growth and the refinement of
established brain structures as a result of specific learning
experiences that vary widely across individuals and cultures.
5
Reflexes
Reflex – an inborn automatic response to a particular form of
stimulation
Some reflexes have an adaptive value – for example rooting
helps a breast-fed baby find its mother’s nipples.
Babies are born with a variety of reflexes which will become
voluntary actions. Some such as rooting and sucking are vital
for survival as it allows the infant to feed. Grasping on the
other hand helps in relationships.
Most newborn reflexes disappear by six months of age.
Researchers believe that this is due to growth of the cerebral
cortex.
6
States of Arousal
Different degrees of sleep and wakefulness; infants move in and
out of throughout the day and night.
5 states –REM and NREM sleep; drowsiness; Quiet Alert
(Awake) and Active Alert (Awake/Crying)
Individual differences exist that affect parents’ attitudes toward
and interaction with baby.

6. During birth and 2 years, the organization of sleep and
wakefulness changes a great deal. Total sleep time will decline.
Changing arousal patterns are due to brain development as well
as the infant’s social environment. Cultural differences are also
apparent with regards to how parents try to get their infants to
sleep.
7
States of Arousal, cont.
Sleep
During irregular or REM sleep, the brain and parts of the body
are active. Eyes dart beneath lids and heart rate, blood pressure
and breathing are uneven.
REM accounts for 50% of newborn’s sleep time.
With REM sleep it will decline by 3 to 5 years of age to an
adult-like level of 20%
Believed special need for the stimulation of REM sleep as spend
little time in the alert state – REM sleep seems to be the way
the brain stimulates itself. It also protects the health of the eye;
as it causes the viterous to circulate. This circulation delivers
oxygen to parts of the eye.
8
States of Arousal, cont

7. During regular (NREM) sleep, the body is quiet and heart rate,
breathing, and brain wave activity are slow and regular.
9
States of Arousal, cont.
Drowsiness – state between awake and sleep and vice versa.
Eyes appeared glazed and unfocused
Transition state
Drowsiness is a transitional state between wake and sleep.
10
States of Arousal, cont.
Quiet Awake/Alert
Eyes open and focused
Body at rest
Best state for taking in environment

8. 11
States of Arousal, cont.
Wake Activity/Crying
Crying : 1st way babies
communicate their needs
Stimulates strong feelings
of arousal and discomfort
in adults.
Usually cry because of physical needs. Crying typically
increases during the early weeks, and then declines. Because
this trend appears in many cultures, researchers believe that
normal readjustments of the central nervous system underlie it.
Although parents do not always interpret their baby’s cry
correctly, their accuracy improves with age.
There are many ways to soothe a crying baby; most effective in
western cultures is lifting the baby to your shoulder and rocking
or walking. Another common method is swaddling – wrapping
the baby tightly in a blanket.
Colic or persistent crying has an unknown cause but generally
subsides between 3 and 6 months.
12
Sensory Capacities

9. Touch
Helps stimulate physical
and emotional development
Sensitivity to touch, pain,
and temperature change
Is a fundamental means of interaction between parent and child.
13
Sensory capacities, cont.
Taste
Babies are born with
the ability to communicate
their taste preferences
Infant facial expressions
indicate they can distinguish
among several tastes
(sweet, salty, bitter, sour)
Infants prefers sweet tastes!
14
Sensory capacities, cont.
Smell

10. Responsiveness of infants to the smell of certain foods is
similar to that of adults – some odor preferences are innate
Newborn infant is attracted to the odor of own mother’s
lactating breast. This helps her to find a food source and
identify own mom.
Odor preferences are also apparent at birth.
15
Sensory capacities, cont.
Hearing
Newborns prefer complex sounds such as voices and noises.
Infants can discriminate among most speech sounds.
Ability to perceive speech sounds outside their language is more
precise than an adult’s.
Prefer speech that is high-pitched and expressive.
Infants make rapid progress in perceiving the structure of
speech. Research shows they have an impressive learning
capacity. By analyzing the speech stream for patterns
(regularly occurring sequences of sounds) infants acquire a
stock of speech structures for which they will later learn
meanings.

11. Infants’ special responsiveness to speech encourages parents to
talk to their infants. This will strengthen the infants’ readiness
for speech and the emotional bond with the parent or caregiver.
16
Sensory capacities, cont.
Vision
Least mature of senses.
Cannot focus their eyes very well.
Visual acuity (fineness of discrimination) is limited.
Explore environment by scanning it for interesting sights and
tracking moving objects.
Prefer colored rather than gray stimuli
At birth infants perceive objects at a distance of 20 feet about
as clearly as adults do at 600 feet. Newborns see unclearly
across a wide range of distances.
By 2 months can focus on objects as well as adults.
By 4 months can discriminate colors.
17
Learning Capacities
Classical Conditioning
Operant Conditioning
Habituation

12. Imitation
Newborn reflexes make classical conditioning possible.
Classical Conditioning helps infants recognize which events
usually occur together in the everyday world so they can
anticipate what is about to happen next.
Operant conditioning – infants act or operate on the
environment and the stimuli that follow their behavior change
the probability that the behavior will occur again. Generally a
stimulus that increases the behavior occurring again is a
reinforcer. Removing the desired stimulus or presenting an
unpleasant one to decrease the occurrence is called punishment.
Habituation gradual reduction in the strength of a response due
to repetitive stimulation. For example – your roommate snores
but after a few weeks you no longer “hear” it.
Please read further on pages 140-142.
Imitation – copying the behavior of another individual.
18
Motor Development
Gross motor refers to
control over actions that
help an infant move
around (i.e. crawling).
Fine motor refers to
control over smaller
movements, such as

13. reaching and grasping.
Motor skills as dynamic systems:
Mastery of motor skills involves acquiring increasingly complex
systems of actions. When motor skills work as a system,
separate abilities blend together, each cooperating with others
to produce more effective ways of exploring and controlling the
environment.
19
Nutrition
Infant’s energy needs are twice as great as those of an adult.
25% of an infant’s caloric intake is devoted to growth.
If diet is deficient in either quantity or quality, growth can be
permanently stunted.
Because of rapid growth infants need an adequate diet. More on
this in the next unit.
20
Breastfeeding
Provides the correct balance of fat and protein
Nutritionally complete
Helps ensure healthy physical growth
Protects against many diseases
Protects against faulty jaw development and tooth decay

14. Digestibility
Transition to solid food
21