Chapter 4: Infancy

Discovering the Lifespan - Robert S. Feldman

Chapter 4: Infancy

Module 2Physical Development

in Infancy

GROWTH AND STABILITY

Physical Growth

• Rapid growth during first two years

An Interesting Head Count

Nervous System and Brain

• Nervous system comprises the brain and the nerves that extend throughout the body

• Neurons are the basic cells of the nervous system

Quick Check

• Neurons• Dendrites• Axons• Neurotransmitters• Synapses

Brain Physiology

• Structure and function– Forebrain – Cerebral cortex has four lobes

• Two hemispheres usually work together and each lobe has a primary function• Frontal, occipital, temporal, parietal lobes

– Amygdala– Hippocampus

The Brain

Fig. 3.7

The Brain’s

Four Lobes

Functions of Lobes of the Cortex

Frontal lobes

Occipital lobes

Temporal lobes

Involved in voluntary movement, thinking, personality, and intentionality or purpose

Function in vision

Active role in hearing, language processing, and memory

Parietal lobes Roles in registering spatial location, attention, and motor control

The Brain

Development of the Brain • By age 6, almost adult size.• Brain growth spurts: coincide with changes

in cognitive behavior• Cerebellum, largest part of brain, divides into

halves• Lateralization, specialties of each

hemisphere; left: language and logical thinking; right: visual and spatial functions

Brain Physiology

• Neurons — nerve cells handling information processing at the cellular level– Axon, dendrites, synapses – Neurotransmitters: dopamine– Myelin sheath and myelination– Neural circuits

• Lateralization — specialization of functions in one hemisphere of cerebral cortex

The Brain

The Neuron

The Brain

Fig. 3.8

The Brain In Infancy

• Shaken Baby Syndrome• Extensive brain development in utero

– Born with about 100 billion neurons– Enriched early experiences can enhance brain growth and functioning– Brain flexibility and resilience demonstrated in deprived environments

• Experience determines brain connections – Enriched and deprived environments

The Brain

• Changing neurons– Myelination; visual and auditory

– Rapid growth of myelin sheath, dendrite and synapse connections

– Blooming and pruning of connections in brain

– Peak synaptic overproduction influenced by heredity and environment

The Brain

• At birth, greater activity in left hemisphere specializes as infants listen to speech

• Motor control begins about 2 months

• Brain areas do not mature uniformly; skills affected by myelination and interconnections

The Brain

Major Systems of the Brain

• Brain stem• Limbic system• Cerebral cortex

How great brains grow!• Birth:

– 100-200 billion neurons

– Relatively few neurons-neuron connections

• During first two years:– Billions of new

connections established and become more complex

Use it or lose it!

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

• Myelin88

Form and Function: Brain Growth

• Neurons reposition themselves with growth, becoming arranged by function – Cerebral cortex– Subcortical levels

Don’t shake the baby!

• Shaken Baby Syndrome– Brain sensitive to form forms of injury– Shaking can lead to brain rotation within

skull• Blood vessels tearsevere medical

problems, long-term disabilities, and sometimes death

Environmental Influences on Brain Development

• Plasticity• Sensitive period

Critical Period: specific time when a given event (or absence) has specific impact on development. Not absolutely fixed.

Plasticity: ability to modify Sensitive Periods: especially

responsive to specific type of experience

Without feedback from the environment (that is, without experience) how can further development occur?

A child raised in a deprived

environment with inadequate stimulation and feedback might fail to learn. The damage to a child is significant when love and attention are absent.

Critical & Sensitive PeriodsCritical and sensitive periods are

both times when the organism is biologically primed to most benefit from a particular experience.

Sensitive Periods: adverse effects

caused by missing a sensitive period may be overcome at a later time, although with great difficulty.

Critical Periods: adverse effects caused by missing a critical period are permanent.

The only clearly demonstrated critical period

in human beings involves early stimulation of certain neural and body cells. Without such stimulation, these cells atrophy and die (e.g., visual neurons must have light during their early development or they will die.

Depth perception may occur as well.

The first 5 to 6 years of childhood may be a critical period for the development of the brain.

Even when a part of the brain is damaged, if damage occurs before age 5/6, the brain may compensate and take over the functions. After age six, highly unlikely.

Other ways a child may suffer permanent disability by early childhood:

1. occurrence of irreparable physical damage upon which later development will depend

2. a critical period that passes without the child’s obtaining the necessary experience or stimulation

3. a situation where the child is kept by their culture or environment from ever obtaining the learning necessary for proper development.

Do Baby Einstein programs really work?

What do babies do all day?

Life Cycles of Infancy• Wake• Sleep• Eat• Defecate

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

Sleep: Perchance to Dream

• Major state– 16-17 hours daily (average); wide variations

• 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

(See table 2-2)90-91

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

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– Low APGAR scores– Mother’s smoking– Some brain defects– Child abuse

SIDS is found in children of every race and socioeconomic group and in

children who have had no apparent health problems

Back-to-sleep is important!

Review and ApplyREVIEW• The major principles of growth are the

cephalocaudal principle, the proximodistal principle, the principle of hierarchical integration, and the principle of the independence of systems.

• The development of the nervous system first entails the development of billions of neurons and interconnections among them. Later, the numbers of both neurons and connections decrease as a result of the infant’s experiences.

Review and ApplyREVIEW• Babies integrate their individual behaviors

by developing rhythms—repetitive, cyclical patterns of behavior.

Review and Apply

APPLY• What evolutionary advantage could there

be for infants to be born with more nerve cells than they actually need or use? How might our understanding of synaptic “pruning” affect the way we treat infants?

MOTOR DEVELOPMENT

Reflexes: Inborn Physical Skills

• Reflexes: learned, organized involuntary responses that occur automatically in presence of certain stimuli

What did you see?

• Take two minutes to list the reflexes you saw in the clip.

Why do reflexes come and go?

Ethnic and Cultural Differences and Similarities in Reflexes

• Reflexes– Genetically determined– Universal

• Cultural variations in ways displayed– Moro reflex

• Serves– Diagnostic tool– Social function– Survival function

Motor Development in Infancy

Milestones of Normal Motor Development

Motor Development in InfancyFine Motor Skills

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

• Children living in many developing countries

• Slower growth rate • Chronically malnourished during infancy =

later lower IQ score

Are problems of malnourishment restricted to

developing countries?

When Malnutrition Is Severe

• Maramus• Kwashiorkor

Nonorganic Failure to Thrive

• Sufficient nutrition• Symptoms • Reversal

“A fat babyis a

healthy baby”?

Is Breast Best?

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– Cerealstrained fruits

Review and Apply

REVIEW• Reflexes are universal, genetically acquired physical behaviors.• During infancy children reach a series of milestones in their physical development on a fairly consistent schedule, with some individual and cultural variations.

Review and ApplyREVIEW

• Nutrition strongly affects physical development.

• The advantages of breast-feeding are numerous.

Review and Apply

APPLY• What advice might you give a friend who is concerned that her infant is still not walking at 14 months, when every other baby she knows started walking by the first birthday?

Learning the World

• Sensation• Perception

Visual Perception: Seeing the World

• Newborn’s distance vision ranges from 20/200 to 20/600

• 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

Auditory Perception: The World of Sound

• Infants – Hear before birth and have good auditory

perception after they are born– 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

sounds103

Smell and Taste in a Small World

• Smell– Well developed at birth– Helps in recognition of mother early in life

• Taste– Have innate sweet tooth– Show facial disgust at bitter taste– Develop preferences based on what mother

ate during pregnancy

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

Becoming an Informed Consumer of Development

Exercising Your Infant’s Body and Senses• Attempts to accelerate physical and sensory-

perceptual development yield little success »Yet

• Infants need sufficient physical and sensory stimulation

How can this be accomplished?

• Carry a baby in different ways• Let infants explore their environment• 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

Review and ApplyREVIEW• Infants’ sensory abilities are surprisingly well developed

at or shortly after birth. Their perceptions help them explore and begin to make sense of the world.

• Very early, infants can see depth and motion, distinguish colors and patterns, localize and discriminate sounds, and recognize the sound and smell of their mothers.

• Infants are sensitive to pain and touch, and most medical authorities now subscribe to procedures, including anesthesia, that minimize infants’ pain.

Chapter 4: Infancy

Documents

Transcript of Chapter 4: Infancy

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