physical development chapter 6. prolonged period of physical growth prolonged period of physical...

Physical Physical DevelopmentDevelopment

Chapter 6Chapter 6

Prolonged period of physical growthProlonged period of physical growth Period between birth/puberty Period between birth/puberty

mice/rats (2% of lifespan)mice/rats (2% of lifespan) 7 years in chimpanzees (17% of 7 years in chimpanzees (17% of

lifespan)lifespan) 20% of total years to growth20% of total years to growth Why?Why?

Changes in Body SizeChanges in Body Size

Rapid changes during infancyRapid changes during infancy– By end of first year, height 50% greater By end of first year, height 50% greater

than birththan birth– End of second year, 75% greaterEnd of second year, 75% greater– Weight shows similar gainsWeight shows similar gains– If rate maintained, children would be 10 If rate maintained, children would be 10

feet tall and weigh over 200 pounds by feet tall and weigh over 200 pounds by age 10; 12 feet tall and weigh several age 10; 12 feet tall and weigh several tons by age 18tons by age 18

Changes in Body SizeChanges in Body Size

Slows in early and middle childhoodSlows in early and middle childhood

Sharp acceleration in pubertySharp acceleration in puberty

• Figure 6.1 Gain in height per year by males and females from birth through adolescence. At age 10 ½ , girls begin their growth spurt. Boys follow some 2 ½ years later and grow faster than girls once their growth begins. BASED ON TANNER, WHITEHOUSE, & TAKAISHI, 1966.

Changes in Body Changes in Body ProportionsProportions

Different ratesDifferent rates CephalocaudalCephalocaudal ProximodistalProximodistal Exceptions to growth trends in Exceptions to growth trends in

adolescenceadolescence

Changes in Body Changes in Body ProportionsProportions

Body proportions similar in infancy Body proportions similar in infancy and childhoodand childhood

Major differences occur during Major differences occur during adolescenceadolescence

Changes in Body Changes in Body CompositionComposition

Changes in muscle-fat makeupChanges in muscle-fat makeup Body fat increases pre/postnatallyBody fat increases pre/postnatally Peak 9 monthsPeak 9 months Slender starting in second year until Slender starting in second year until

middle childhoodmiddle childhood


Girls more body fat at birth – Girls more body fat at birth – increasesincreases

Around 8, changes begin through Around 8, changes begin through puberty for girlspuberty for girls

Opposite happens for boysOpposite happens for boys


Muscle different rate than fatMuscle different rate than fat Infancy/childhood Infancy/childhood slow slow Adolescence Adolescence rises rises In children, muscle composes 18-24% In children, muscle composes 18-24%

of body weight for both males and of body weight for both males and femalesfemales

By their mid-twenties, percent of body By their mid-twenties, percent of body that is muscle averages 24% for that is muscle averages 24% for females and about 40% for malesfemales and about 40% for males


Both sexes gain muscle at puberty, Both sexes gain muscle at puberty, gain is greater for boysgain is greater for boys– Develop larger skeletal musclesDevelop larger skeletal muscles– Larger heartsLarger hearts– Greater lung capacityGreater lung capacity– Number of blood cells increasesNumber of blood cells increases– Thus…?Thus…?

Skeletal DevelopmentSkeletal Development

Different ratesDifferent rates Skeletal ageSkeletal age Embryonic skeleton Embryonic skeleton cartilagecartilage Beginning at 6Beginning at 6thth week of pregnancy, week of pregnancy,

bones harden (bones harden (ossifyossify) – process ) – process continues throughout childhood and continues throughout childhood and adolescenceadolescence

Skeletal DevelopmentSkeletal Development

Skull Skull fontanellesfontanelles and and suturessutures Ankles, feet, wrists, hands develop Ankles, feet, wrists, hands develop

more bones more bones

Individual and Cultural Individual and Cultural DifferencesDifferences

Most differences within normal rangeMost differences within normal range Children at extremesChildren at extremes What accounts for differences in What accounts for differences in

growth?growth? Secular trends in physical growthSecular trends in physical growth

Individual and Cultural Individual and Cultural DifferencesDifferences

May be due to improved nutrition May be due to improved nutrition and healthand health– Orphaned babies from developing Orphaned babies from developing

countries countries – Low-income childrenLow-income children– Regions where poverty, famine, and Regions where poverty, famine, and

disease are widespreaddisease are widespread

Development of the BrainDevelopment of the Brain

100-200 billion neurons100-200 billion neurons Neural tube of embryoNeural tube of embryo Migrate and differentiateMigrate and differentiate By end of second trimester, By end of second trimester, mostmost

neurons are formedneurons are formed– Produce neurons?Produce neurons?– Brain can compensateBrain can compensate


SynaptogenesisSynaptogenesis– Infants more connections than adultsInfants more connections than adults– Neurons in synapse get crowded and dieNeurons in synapse get crowded and die

Neurons need stimulation to surviveNeurons need stimulation to survive– Synaptic pruningSynaptic pruning


If most neurons are produced If most neurons are produced prenatally, what accounts for prenatally, what accounts for increase in size of brain?increase in size of brain?– Glial cellsGlial cells– Myelinization Myelinization


Cerebral CortexCerebral Cortex– Largest structureLargest structure– Responsible for intelligenceResponsible for intelligence– Order of developmentOrder of development


3-6 3-6 frontal lobes frontal lobes 6-puberty 6-puberty temporal and parietal temporal and parietal

lobeslobes

MRIs were used to compare brain MRIs were used to compare brain activity in adolescents (10-18) and activity in adolescents (10-18) and adults (20-40) while processing adults (20-40) while processing emotional informationemotional information


LateralizationLateralization– When does it occur?When does it occur?– Tells us about brain plasticityTells us about brain plasticity– Lateralization has already begun at birthLateralization has already begun at birth– Lateralization not complete…Lateralization not complete…

Motor DevelopmentMotor Development

Sequence of motor skills sameSequence of motor skills same Large individual variationLarge individual variation Rate of motor development Rate of motor development ≠ ≠ future future

development outcomesdevelopment outcomes


Gross motor developmentGross motor development

Fine motor developmentFine motor development

• Table 6.1 Age Norms (in Months) for Important Motor Developments (Based on

European American, Latino, and African American Children in the United States)


Not a series of isolated, unrelated Not a series of isolated, unrelated accomplishmentsaccomplishments

Cross-cultural researchCross-cultural research


Beyond Infancy: Motor Development Beyond Infancy: Motor Development in Childhood and Adolescencein Childhood and Adolescence– Each year, skills improveEach year, skills improve

Large muscles, eye-hand coordinationLarge muscles, eye-hand coordination

– Young children Young children overestimateoverestimate– Puberty – males increase in muscle Puberty – males increase in muscle

development; females tend to become development; females tend to become less activeless active

Hormonal Influences on Hormonal Influences on Physical GrowthPhysical Growth

Physical changes Physical changes endocrine endocrine systemsystem

HormonesHormones Pituitary glandPituitary gland Growth hormone (GH)Growth hormone (GH)


GH GH body tissues except CNS and body tissues except CNS and genitalsgenitals

No prenatal growth, essential from No prenatal growth, essential from birth onbirth on

Lack GH Lack GH average mature height of average mature height of 4 feet 4 inches4 feet 4 inches

Catch-up growthCatch-up growth


Sexual maturation Sexual maturation pituitary pituitary secretionssecretions

Estrogens Estrogens female hormones female hormones Androgens Androgens male hormones male hormones Both in each sex, different amountsBoth in each sex, different amounts


Boys’ testes release large quantities Boys’ testes release large quantities of testosterone, which leads to of testosterone, which leads to muscle growth, body and facial hair, muscle growth, body and facial hair, and other male sex characteristics, and other male sex characteristics, also contributes to gains in body sizealso contributes to gains in body size

Estradiol causes the breasts, uterus, Estradiol causes the breasts, uterus, and vagina to mature and the body and vagina to mature and the body to take on feminine proportions, also to take on feminine proportions, also help regulate menstrual cyclehelp regulate menstrual cycle


Adrenal androgensAdrenal androgens Not sure what sets hormonal Not sure what sets hormonal

processes in motionprocesses in motion– Combination of heredity, hormones, and Combination of heredity, hormones, and

body fatbody fat

• Figure 6.10 Hormonal influences on physical development.


In girls, rise in body weight and fat In girls, rise in body weight and fat appears to play a role in sexual appears to play a role in sexual maturationmaturation– Serious athletic training/eat littleSerious athletic training/eat little– OverweightOverweight– Body fat Body fat ≥ 17%≥ 17%– Athletes, eating disordersAthletes, eating disorders

PubertyPuberty

Physically mature; produce offspringPhysically mature; produce offspring Changes in physical features related Changes in physical features related

to sexual functioningto sexual functioning– Primary sexual characteristicsPrimary sexual characteristics– Secondary sexual characteristicsSecondary sexual characteristics

PubertyPuberty

BoysBoys– Early maturation: advantaged in Early maturation: advantaged in

emotional and social functioning (seen as emotional and social functioning (seen as more relaxed, independent, self-more relaxed, independent, self-confident, and physically attractive; also confident, and physically attractive; also tend to be more popular, hold leadership tend to be more popular, hold leadership positions, and are athletic stars)positions, and are athletic stars)

– Late maturation: not well liked (seen as Late maturation: not well liked (seen as anxious, overly talkative, and attention anxious, overly talkative, and attention seekers)seekers)

PubertyPuberty

GirlsGirls– Early maturation: social difficulties (below Early maturation: social difficulties (below

average in popularity, withdrawn, lack self-average in popularity, withdrawn, lack self-confidence, hold few positions of leadership, confidence, hold few positions of leadership, more likely to be depressed, smoke/drink, have more likely to be depressed, smoke/drink, have an eating disorder)an eating disorder)

– Late maturation: physically attractive, lively, Late maturation: physically attractive, lively, sociable, leaders at schoolsociable, leaders at school

Advantages of maturing early and the Advantages of maturing early and the disadvantages of maturing late are greater disadvantages of maturing late are greater for boys than for girlsfor boys than for girls

Heredity vs. EnvironmentHeredity vs. Environment

Heredity Heredity hormones hormones NutritionNutrition

– Dietary diseasesDietary diseases MarasmusMarasmus KwashiorkorKwashiorkor

Infectious diseaseInfectious disease

Heredity vs. EnvironmentHeredity vs. Environment

Emotional Well-BeingEmotional Well-Being– Nonorganic failure to thriveNonorganic failure to thrive– Deprivation dwarfismDeprivation dwarfism

physical development chapter 6. prolonged period of physical growth prolonged period of physical...

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