Transcript Chapter 4 as PowerPoint

CHAPTER 4
PHYSICAL DEVELOPMENT IN
INFANCY
Learning Objectives
GROWTH AND STABILITY
Physical Growth:
The Rapid Advances of Infancy
Infants grow at a rapid pace over the first two years of their
lives (see Figure 4-1)
• 5 months: average birth weight doubles to around 15 #
• 1 year: weight triples to about 22 pounds
• End of 2nd year: average child weighs around four times
as much as at birth
How they grow…
Continuous
Physical Growth:
The Rapid Advances of Infancy
Not all parts of an infant's body grow at the same rate
• At Birth:
head accounts for one-quarter of newborn's entire body
• During 1st & 2nd year:
rest of the body begins to catch up
An Interesting Head Count
There are gender and ethnic differences in
infant weight and length
• Girls generally are slightly shorter than boys
• Girls weigh slightly less than boys
• Gender differences remain throughout childhood
• Asian infants tend to be slightly smaller than
NA Caucasian infants
• African-American infants tend to be slightly bigger than
NA Caucasian infants.
Physical Growth:
The Rapid Advances of Infancy
4 Principles
Nervous System and Brain:
A Foundation of Development
• Neurons are the
basic cells of the
nervous system
• Nervous system
comprises the brain
and the nerves that
extend throughout the
body
Brain Development
Prenatal
• Neurons multiply at an amazing rate prior to birth.
• At some points in prenatal development, cell division
creates some 250,000 additional neurons every minute.
Birth
• 100-200 billion neurons
• Relatively few neurons-neuron connections
During first two years
• Billions of new connections established and become
more complex
Adult
• A single neuron is likely to have a minimum of 5,000
connections to other neurons or other body parts.
Babies are born with many more neurons than they need
Use it or lose it!
Although synapses are formed throughout life, based on our
changing experiences, the billions of new synapses infants form
during the first two years are more numerous than necessary
• Synaptic pruning
– Unused neurons are eliminated
– Allows established neurons to build more elaborate
communication networks with other neurons
– Development of nervous system proceeds most effectively
through loss of cells
• Myelination
• “Insulation” of the wiring
• Protects & speeds information conduction
• Activity-dependent effects on myelination cannot be
considered strictly a developmental event.
(Fields, D.,Myelination: An Overlooked Mechanism of Synaptic Plasticity? Neuroscientist 2005)
Neuron Networks
Over the first two years of life, networks of neurons
become increasingly complex and interconnected.
Coming to terms with your brain…
Form and Function: Brain Growth
Neurons reposition themselves with growth, becoming
arranged by function
• Cerebral cortex
– upper layer of the brain
– higher-order processes: thinking & reasoning
– become more developed and interconnected
• Subcortical levels
– Lower layers of the brain
– regulate fundamental activities: breathing & heart rate
– most fully developed at birth.
Brain Development: Influences and Definitions
Brain
Development
• Environmental
Influences
Brain
Development
• Sensitive
Period
a specific, but limited, time,
usually early in an organism's
life, during which the organism
is particularly susceptible to
environmental influences
relating to some particular
facet of development
Brain
Development
• Plasticity
the degree to which a
developing structure or
behavior is modifiable
due to experience
What do babies do all day?
Integrating the bodily systems: Life cycles of infancy
• Rhythms: repetitive, cyclical patterns of behavior
– Wake
– Sleep
– Eat
– Eliminate
Initially like separate individuals all playing their own melody.
Eventually they become like a jazz band still playing their
own riff but weaving a single, harmonious, song.
Rhythms and States
State
• One of major body rhythms
• Degree of awareness infant displays to both internal and
external stimulation
• Change in state alters amount of stimulation required to
get infant's attention
• Electrical brain waves can be measured by
electrocephalogram (EEG)
Primary Behavioral States
Primary Behavioral States
Sleep: Perchance to Dream
Major state
• 16-17 hours daily (average); wide variations
• heart rates increase and become irregular, their blood
pressure rises, and they begin to breathe more rapidly
Different than adult sleep
• 2 hour spurts; periods of wakefulness
• Cyclic pattern
• By 16 weeks sleep about 6 continuous hours; by 1 year
sleep through night
Cycle of Infant Behavioral States
•
•
•
•
Awake
Non-alert
Fussing
Crying
Awake
Transition between
Sleeping and
Waking
• Drowse
• Daze
• Sleep-Wake
Transition
Transitional Sleep
States
• Active
• Quiet
• Active-Quiet
Transition
Sleep
Sleep
REM Sleep
• Period of active sleep
• Closed eyes begin to move in a back-and-forth pattern
• Takes up around one-half of infant sleep
• May provide means for brain to stimulate itself through
autostimulation
• In Adults correlated with memory storage Why not in
babies too?
REM Sleep Through the Lifespan
• the Kipsigis of Africa, infants sleep with their
mothers and are nurse whenever they wake.
• They accompany their mothers during daily chores,
napping while strapped to their mothers’ backs
• Kipsigis infants do not sleep through the night until
much later than babies in Western societies,
• the first 8 months of life, they seldom sleep longer
than 3 hours at a stretch.
• In comparison, 8-month-old infants in the United
States may sleep as long as 8 hours at a time
Much like US breast fed kids
Did you find examples in the text that suggest
that cultural practices affect infants’ sleep
patterns?
SIDS: The Unanticipated Killer
• Sudden infant death syndrome (SIDS) is a disorder in
which seemingly healthy infants die in their sleep
• SIDS strikes about 2,500 infants in the United States
each year
• Although it seems to occur when the normal patterns of
breathing during sleep are interrupted, scientists have
been unable to discover why that might happen
SIDS
Sudden Infant Death Syndrome
• Leading cause of death in children under 1 year of age
• Back-to-sleep guidelines (AAP)
• Differential risk
• Boys
• African American infants
• Low birthweight
• Don’t shut the nursery door!
• Low APGAR scores
• Use your EARS!
• Mother's smoking
• Some brain defects
• Child abuse
Declining Rates of SIDS
SIDS is found in children of every race and
socioeconomic group and in children who
have had no apparent health problems
• SIDS strikes about 1 in 1,000 infants in the USA each year.
• Although it seems to occur when the normal patterns of
breathing during sleep are interrupted, scientists have been
unable to discover why that might happen.
• American Academy of Pediatrics now suggests that
– babies sleep on their backs rather than on their sides or
stomachs—called the back-to-sleep guideline.
– parents consider giving their babies a pacifier during naps
and bedtime.
Back-to-sleep is important!
MOTOR DEVELOPMENT
Motor Development
• Shape and proportions of newborn babies are simply not
conducive to easy mobility
• Young infants lack the strength to raise large heads
• Movement is further impeded because limbs are short in
relation to the rest of the body
• Infant bodies are mainly fat, with a limited amount of
muscle; the result is a lack strength
Motor Development
BUT
• At birth newborns have an extensive repertoire of
behavioral possibilities brought about by innate reflexes,
and their range of motor skills grows rapidly during the
first two years of life
Reflexes: Inborn Physical Skills
Reflexes
• Learned, organized involuntary responses that occur
automatically in presence of certain stimuli
WHAT?
No, No! Reflexes are wired up unlearned responses to stimuli!
Some Basic Reflexes in Infants
Some Basic Reflexes in Infants
Why do neonate reflexes come and go?
1. Evolutionary explanations of development: gradual
disappearance of reflexes to result of increase in
voluntary control over behavior that occurs as infants
become more able to control their muscles.
2. It may be that reflexes form the foundation for future,
more complex behaviors. As these more intricate
behaviors become well learned, they encompass the
earlier reflexes.
3. Perhaps reflexes stimulate parts of the brain responsible
for more complex behaviors, helping them develop.
Intensive practice of motor behaviors
• May produce earlier appearance of certain
motor activities
• No evidence the activities are performed
qualitatively better
• Even when early gains are found
• Do not produce a child w/ better motor skills
• Do not produce an adult w/ better motor skills.
Ethnic and Cultural Differences and Similarities
in Neonatal Reflexes
Reflexes
• Genetically determined
• Universal
Cultural variations in ways displayed
• Moro reflex
Serves
• Diagnostic tool
• reflexes emerge and disappear on a regular timetable
• their absence—or presence—at a given point of infancy
• a clue that something’s wrong in an infant's development.
• Social function
• Survival function
Moro Reflex: Some differences reflect cultural
and ethnic variations
Moro Reflex (Startle Reflex) - stretch out the
arms, flex the legs, and grab.
• Caucasian infants show a pronounced response.
– Also cry and respond in a generally agitated manner.
–
• Navajo babies react much more calmly.
– Arms do not flail out as much and rarely cry.
Milestones of Motor Development
• Fifty percent can perform each skill at the month
indicated in the figure.
• Timing at which each skill appears varies widely.
• 24% walk well at 11.1 months
• 90% by 14.9 months
Motor Progress
• Young infants still are able to accomplish some kinds of movement.
• When placed on their stomachs they wiggle their arms and legs and may try
to lift their heavy heads.
• As their strength increases, they are able to push hard enough against the
surface on which they are resting to propel their bodies in different
directions.
• They often end up moving backwards rather than forwards, but by the age
of 6 months they become rather accomplished at moving themselves in
particular directions.
• These initial efforts are the forerunners of crawling, in which babies
coordinate the motions of their arms and legs and propel themselves
forward.
• Crawling appears typically between 8 and 10 months.
• Walking comes around the age of 9 months; most infants are able to walk
by supporting themselves on furniture, and half of all infants can walk well
by the end of their first year of life.
• Most are able to sit without support by the age of 6 months.
Dynamic Systems
Dynamic systems theory
• Describes how motor behaviors are assembled
– Motor skills do not develop in vacuum
– Each skill advances in context of other motor abilities
– As motor skills develop, so do non-motoric skills
• Theory places emphasis on child's own motivation (a
cognitive state) in advancing important aspects of motor
development
Developmental Norms
Comparing Individual to Group Norms:
• Represent the average performance of a large sample of
children of a given age
• Permit comparisons between a particular child's
performance on a particular behavior and the average
performance of the children in the norm sample
• Must be interpreted with caution
• Brazelton Neonatal Behavior Assessment Scale (NBAS)
Nutrition in Infancy
Fueling Motor Development
• Without proper nutrition, infants cannot reach physical
potential and may suffer cognitive and social
consequences
• Infants differ in growth rates, body composition,
metabolism, and activity levels
So what is a healthy caloric allotment for
infants?
• About 50 calories per day for each pound of weight
• Most infants regulate their caloric intake quite effectively
on their own
• If are allowed consume as much they seem to want, and
not pressured to eat more, they will be healthy
Malnutrition
Malnutrition
• Condition of having improper amount and balance of
nutrients, produces several results, none good
• More common in children living in developing countries
• Slower growth rate
• Chronically malnourished during infancy
• later lower IQ score
• Do less well in school
• Effects linger even after improved diet
Underweight Children
Percent under five years who are moderately or severely underweight.
Are problems of malnourishment restricted to
developing countries?
Undernutrition: Dietary Deficiencies
• Undernutrition also has long-term costs, including mild to
moderate cognitive delays
• Up to 25% of 1- to 5-year-old US children have diets that
fall below minimum caloric intake recommended by
nutritional experts
• 1/5 of US children go to bed hungry.
• Do you believe these “statistics”?
When Malnutrition Is Severe
Maramus
Kwashiorkor
• Malnutrition in first year
• Infants stop growing.
• Attributable to severe
deficiency in proteins and
calories
• Causes the body to waste
away
• Ultimately results in death
• Found in older children
• Child's stomach, limbs,
and face swell
• Body struggles to make
use of few available
nutrients
Nonorganic Failure to Thrive
• Sufficient nutrition
• but are deprived of attention and stimulation.
• Symptoms
• underdevelopment, listlessness, and apathy
• usually occurs by age 18 months.
• Reversal
• possible through intensive parent training
• or removal to emotionally supportive environment.
“A fat baby is a healthy baby.” Really?
• Not necessarily.
• No clear correlation between obesity during infancy and
obesity at 16 years
• BUT - some research suggests overfeeding during
infancy may lead to the creation of an excess of fat cells
• remain in the body throughout life
• may predispose a person to be overweight.
• Weight gain during infancy may relate to weight at 6
• Weight at 6 associated with adult obesity.
Is Breast Best?
Starting around the 1940s, the general belief among
“child care experts” was that breast-feeding was an
obsolete method that put children unnecessarily at risk.
Bottle-feeding argument:
• keep track of amount of milk baby was receiving
• could ensure that child got sufficient nutrients.
• helped mothers keep feedings to rigid schedule of one
bottle every 4 hours (the recommended at that time)
• Mothers who breast-fed their babies could never be
certain just how much milk their infants were getting.
Is Breast Best?
Breast-feeding argument:
• First 12 mos no better food for an infant than breast milk.
• Contains all the nutrients necessary for growth
• Offer some immunity to a variety of childhood diseases
• respiratory illnesses
• ear infections
• diarrhea
• allergies.
• More easily digested than cow's milk or formula
• It’s sterile, warm, and convenient for mother to dispense.
• Breast milk may enhance cognitive growth
• Leads to high adult intelligence.
• Babies are more responsive to touch.
Is Breast Best?
For mother:
• lower rates of ovarian cancer and breast cancer prior to
menopause.
• Hormones produced during breast-feeding help shrink
uteruses of women following birth
• enables mom’s bodies to return more quickly to a prepregnancy state.
• Hormones also may inhibit ovulation,
• reducing (but not eliminating!) chance of becoming
pregnant
• thereby helping to space birth of additional children
So What Is the Answer?
Breast milk
• Offers all nutrients infant needs for first 12 months of life
• Is more easily digested than alternative
• Provides some immunity to variety of childhood diseases
• May enhance cognitive growth
• Offers significant emotional advances for mother and
child
• Not cure-all for infant nutrition and health
Introducing Solid Foods: When and What?
• Solids can be started at 6 months but are not needed
until 9 to 12 months (AAFP)
– Introduced gradually, one at a time
– Cerealstrained fruits
• Time of weaning varies greatly in developed and
developing countries
Learning the World
• Sensation
is the physical stimulation of the sense organs
• Perception
is the mental process of sorting out, interpreting, analyzing,
and integrating stimuli from the sense organs and brain
Visual Perception: Seeing the World
• Newborn's distance vision ranges from 20/200 to 20/600
distance vision is 1/10th to 1/3rd that of average adult's.
• By 6 months, average infant's vision is already 20/20
• Other visual abilities grow rapidly
– Binocular vision
– Depth perception
Infant Visual Preference
Preferences that are present
from birth
• Genetically preprogrammed to
prefer particular kinds of stimuli
• Prefer to look at patterned over
simpler stimuli
• Robert Fantz
two- and three-month-old infants
Neonate Visual Preferences
• Prefer
– curved over straight lines
– three-dimensional figures to two-dimensional ones,
– human faces to non-faces.
Such capabilities may be a reflection of the existence of
highly specialized cells in the brain that react to stimuli
of a particular pattern, orientation, shape, and direction
of movement.
• Prefer their own mother's face to other faces;
• Distinguish between male and female faces
Facing the World
Genetics is not the sole determinant
of infant visual preferences
• A few hours after birth, infants have
already learned to prefer their own
mother's face to other faces
•
Similarly, between the ages of six
and nine months, infants become
more adept at distinguishing
•
between the faces of humans, while
they become less able to distinguish
faces of members of other species
•
They also distinguish between male
and female faces
Auditory Perception: The World of Sound
Infants
•Hear before birth and have good auditory perception after birth
•Are more sensitive to certain frequencies
•Reach adult accuracy in sound localization by age 1
•Can discriminate groups of different sounds
•React to changes in musical key and rhythm
•Can discriminate many language related sounds
•Are born with preferences for particular sound combinations which
may be shaped by prenatal exposure to mothers’ voices
Smell and Taste in a Small World
Smell
• Well developed at birth
• Helps in recognition of mother early in life
• Used to distinguish mother's scent (only in breast fed
babies); cannot distinguish father on basis of odor
Taste
• Have innate sweet tooth
• Show facial disgust at bitter taste
• Preferences based on what mother ate during pregnancy
Ouch!
Contemporary Views on Infant Pain
• Today, it is widely acknowledged that infants are born
with the capacity to experience pain
• Developmental progression in reaction to pain
• Infants born with capacity to experience pain; produces
distress
• Exposure to pain in infancy may lead to permanent
rewiring of nervous system resulting in greater sensitivity
to pain during adulthood
The Power of Touch
• Touch is one of most highly developed sensory systems
in a newborn
• Even youngest infants respond to gentle touches
• Several of the basic reflexes present at birth require
touch sensitivity to operate
Multimodal Perception: Combining Individual
Sensory Inputs
New area of study in infant research
• Some researchers argue that sensations are initially
integrated with one another in the infant
• Others maintain that infant's sensory systems are initially
separate and that brain development leads to increasing
integration
• It does appear that by an early age infants are able to
relate what they have learned about an object through
one sensory channel to what they have learned about it
through another
What are affordances?
Perceptible affordances
• Exist where information on actions that are afforded are
perceptible
• These are dependent on language, culture, context, and
experience and vary for different individuals
Becoming an Informed Consumer of
Development
• Exercising Your Infant's Body and Senses
Attempts to accelerate physical and sensory-perceptual
development yield little success
but
infants need sufficient physical and sensory stimulation.
Enrichment
• Carry a baby in different ways
• Let infants explore their environment
Be
Normal!
• Engage in “rough-and-tumble” play
• Let babies touch their food and even play with it
• Provide toys that stimulate the senses, particularly toys
that can stimulate more than one sense at a time
• Expose them to varied social environments