I.  Building blocks of growth and development

            Human grow complex process occurs over many years

            Average U.S. female 5’ 4”, average U.S. male 5’ 9”, but great variability

            Celaic syndrome-- cannot absorb nutrients from food, stunts growth

            Catch-up growth—body’s struggle to get back to genetically programmed size

            Climate impacts growth (colder-shorter and heavier)

            Children’s height increases most in warm months

            A. Endocrine System-- Body’s Hormonal System Secretes Chemical Hormones Directly

                 into Blood Stream

                        1.  Endocrine gland-- key gland of hormone system

                        2.  Pituitary gland

                                    a.  “master” endocrine gland located at base of brain

                                    b.  directly controlled by hypothalamus

                                    c.  triggers release of hormones from all other glands and produces growth


                                    d.  growth hormones-- directly regulate growth

                                                i.    children lacking  growth hormones unlikely to exceed  4’

                                                ii.    adults more effectively treated with growth hormones

                                                iii.   growth hormones in children early and short puberty

                        3.  Thyroid gland-- growth and development and impact on nervous system

                                    deficiency of gland can lead to lower IQ in infants and slower growth

                        4.  Testes-- endocrine glands that produce male hormones testosterone and other


                                                                  a.  testosterone-- specific male hormone released in high quantities during


                                    b.  androgens-- general term for male hormones

                                                responsible for growth, development of male sex organs, and

                                                sexual motivation

                        5.  Ovaries-- estrogen and progesterone

                                    estrogen and progesterone -- key female hormone released in high

                                    quantities during adolescence

                                                i.    keys female growth spurt

                                                ii.    responsible for development of adult sex organs, breasts, and

                                                      pubic hair

                        6.  Adrenal gland-- secretes hormones that contribute to maturation of bones and


                        7.  Endocrine glands continue function throughout life span

            B.  The Nervous System          

                        1.  The nervous system components-- brain, spinal cord, and neural tissue

                                    a.  central nervous system-- brain and spinal cord

                                    b.  peripheral nervous system-- neural tissue extended outside central

                        2.  Neuron-- basic cell unit of nervous system

                                    a.  dendrites-- branches that receive signals from other neurons

                                    b.  axon-- long segment of neuron in which signal is transmitted

                                    c.  synapse-- gap between neurons

                                    d.  neurotransmitter-- brain chemicals released across synapse

                                    e.  myelin-- fatty sheath on axon that insulates and speeds neural


                                    f.  brain has as many as 100 billion neurons

                        3.  Brain development

                                    a.  birth brain weight 25% of adult, age two 75%, age five 90%

                                    b.  deprivation of experience has negative impact on brain

                                                i.    Hubel and Wiesel visually deprived kittens lost function in


                                                ii.    strabismus can affect child’s brain development and vision

                                                iii.   brain has difficulty handing integration of images

                                    c.  plasticity-- neural responsiveness to environmental experience

                                                i.    developing brain highly vulnerable to damage

                                                ii.    greatest in early development (late prenatal and early infancy)

                                                iii.   development is possible throughout life span

                                    d.  lateralization-- increasing dominance of one hemisphere

                                          i.    in most people, left hemisphere adept at sequential processing


                                          ii.    in most people right hemisphere adept at simultaneous processing

                                                 (including  spatial skills and visual-motor ability)

                                                iii.   hemispheres connected by corpus collosum

                                                iv.   if one hemisphere damaged, other may take over

                                                v.   lateralization evident at birth and may have genetic basis

                                                vi.   hemispheric specialization occurs very early

                                                vii. brain never completes development

                                          viii. brain growth spurts occur at times of cognitive advancement            in childhood and adolescence

                                                ix    adult brain weight achieved around age 16

                                                x.   myelination continues well into adulthood

                                                xi.   children can be clever or gifted, but are seldom wise

                                                xii. brain development associated with risky adolescent behavior

                        4.  The aging brain

                                    a.  senility (e.g., Alzheimer’s disease) not normal part of aging

                                    b.  gradual and mild degeneration common

                                    c.  decreased levels of neurotransmitters

                                    d.  loss of brain weight and volume

                                    e.  some loss of neurons common

                                                loss greatest in areas controlling sensory and motor activity

                                    f.  increased senile plaque

                                    g.  reduced blood flow to brain

                                    h.  plasticity continues throughout life span

                                                i.    driven by new experience

                                                ii.    some self-repair possible

                                    i.  performance on some tasks may increase in old age

            C.  Principles of Growth

                        1.  Cephalocaudal principle-- head to tail development

                                    head growth first, then trunk then legs

                        2.  Proximodistal principle-- center outward to extremities

                                    a.  chest and internal organs before arms then fingers

                                    b.  trunk fills out before arms

                        3.  Orthogenetic principle-- global and undifferentiated to increased differentiation

                             and hierarchical integration

                                    single cell to highly specialized cells (e.g., blood)


II. The infant

            A.  Rapid Growth

                        1.  Typical newborn 20” and 7 to 7 1/2 pounds

                        2.  Early size related to prenatal experience

                                    a.  ounce a day, and inch a month gain

                                    b.  growth is in spurts

                        3.  Soft bones ossify (harden) and become interconnected

            B.  Newborn Capabilities

                        1.  Reflexes--  unlearned, involuntary response to stimuli

                                    a.  survival reflexes-- clear adaptive value

                                                breathing, eye-blink, sucking

                                    b.  primitive reflexes--  unclear use

                                                i.    Babinski reflex (toe fanning)

                                                ii.    typically disappear in early infancy

                                                iii.   useful for diagnosing neurological problems

                                                iv.   expression of primitive not related to later expression

                                                v.  primitive tend to disappear during early months of infancy

                                                vi.   controlled by  subcortical part of brain

                                                vii.  disappearance of primitive indicator of normal nervous system


                        2.  Behavioral states-- organized, individual patterns of daily activity

                                    a.  predictable sleep-wake cycles within 6-months after birth

                                                i.    newborns spend half of time in rapid eye movement (REM)


                                                ii.    by 6-months about 25-30% in sleep in REM          

                                                iii.   REM sleep may regulate (reduce) levels of stimulation

                                    b.  states are highly individualized

                        3.  Sensing and learning

                                    a.  sensory systems reasonably functional at birth

                                    b.  infants can learn from experience

                                    c.  capacity to move voluntarily and intentionally is limited

                                                learn slowly

            C.  Physical Behavior

                        1.  Locomotor development

                                    a.  developmental norms-- typical age of mastery

                                                i.    depend on group studied

                                                ii.    hide good deal of variation

                                    b.  principles of growth

                                                i.    cephalocaudal principle, lift head before trunk

                                                ii.    proximodistal principle, trunk activities mastered before leg or

                                                      arm activities

                                                iii.   gross motor skills-- large muscle (e.g., kicking)

                                                iv.   fine motor skills-- hand and feet (e.g., writing)

                                                v.  orthogenetic principle, early use whole body and later use

                                                      specific body part

                                    c.  crawling, walking, manipulating objects

                                                i.    creeping normally begins around 7 months

                                                ii.    hands and knees crawling normally begins around 10 months

                                                iii.   significant increase in ability to explore world

                                    d.  walking normally begins around 1 year

                                                i.    requires mature nervous system, muscle development, and need

                                                      to be less top-heavy

                                                ii.    experience is critical (use of walkers may inhibit walking by

                                                      restricting visual-motor experience)

                        2.  Manipulating objects

                                    a.  innate grasping reflex weakens

                                    b.  pincer grasp-- thumb to forefinger develops

                                    c.  increased integration and differentiated movement

                        3.  Emergence of motor skills

                                    a.  rhythmic stereotypes-- repetitive movement common in early infancy

                                    b.  dynamic systems approach-- use feedback to gain control of motor


                                    c.  walking requires sensory feedback

                                                young toddlers can adjust walking in response to changing body


                                    d.  walking is not simply genetically programmed

                                                requires both nature (maturation) and nurture (sensory and motor



III. The child

            A.  Steady Growth

                        Steady but slower (ages 2-puberty)-- 2-3 inches and 5-6 pounds per year

                        cephalocaudal and proximodistal principles

            B.  Physical behavior

                        1.  Can react to changing world

                        2.  Refinement of motor skills (initially awkward)

                                    a.  can run in a straight line

                                    b.  jump higher, run faster, throw farther

                                    c.  some gender differences (boy slightly better)

                        3.  Improvements in eye/hand coordination often due to practice

                        4.  Faster reaction times

                                    steady improvement across childhood


IV.  The adolescent

     Puberty-- biological change resulting in sexual maturity and capacity to produce children

            A.  Growth Spurt

                        1.  Adolescent growth spurt

                                    a.  triggered by hormones

                                    b.  female peak growth for height around age 12, male peaks age 13.4

                                    c.  female peak weight growth around age 12.5, male peak age 13.9

            B.  Sexual Maturation

                        1.  Due to adrenal gland activity and release of gonadal hormones

                        2.  Gonadal hormones primarily responsible for secondary sex

                             characteristics and sexual maturation

                                    a.  females

                                                i.    menarche--  first menstruation

                                                ii.    normally between ages 11 and 14

                                                iii.   rate differs by ethnicity

                                                iv.   lining of uterus shed

                                                v.  menstruation precedes ovulation

                                                vi.   sexual maturation impacted by ethnicity (e.g., African

                                                      American and Mexican American earlier)

                                    b.  males

                                                i.    process begins with enlargement of testes and scrotum around

                                                      age 11

                                                ii.    semenarche--  initial ejaculation

                                                iii.   production of sperm typically comes after semenarche

                        3.  Variations in timing

                                    a.  boys and girls similar levels of hormones during childhood

                                    b.  boys have larger quantities of male hormones (e.g., androgens)

                                    c.  girls have larger quantities of female hormones (e.g., estrogen)                      

                                    d.  secular trend-- earlier maturation in industrial societies

                                                better medical care and nutrition

                                    e.  anorexia nervosa-- eating disorder involving severe dieting

                                    f.  stress may delay sexual maturation

                                                marital and stress of war can delay sexual maturation

            C.  Psychological Implications

                        1.  Concern with body image

                                    a.  more prominent in females

                                    b.  negative cultural view of menstruation lead to negative image

                                    c.  boys more positive body images

                                    d.  males positive and negative reactions to sexual maturity

                                    e.  changes in relationships with parents

                                                i.    conflict due to increasing independence

                                                ii.    cultural beliefs impact parental relations (e.g., Mexican

                                                      American boys closer to parents)

                                                iii.   relationships tend to become closer after puberty

                        2.  Early versus late development

                                    a.  early maturation more advantageous for boys than for girls

                                                i.    early maturing boys more socially competent, self-assured

                                                ii.    late maturing boys more anxious, less athletic

                                                iii.   early maturing girls less popular, in older peer group

                                                iv.   late maturation for girls not as disadvantageous as for boys

                                    b.  impact of time of maturity tends to fade with time

                                          i.    may be some risk of long-term problems associated with early

                                                maturing girls  who engage in risky behavior (e.g., sex)

                                          ii.    early maturing males may be more conforming 

                                    c.  timing-of-puberty effect mediated by adolescent’s perceptions

                                                peer and family reactions can impact perception

            D.  Physical Behavior

                        Muscular strength and physical competence increases

                                    a.  boys outperform girls (differences driven by biological and social


                                    b.  gap between male and female physical skills narrowing


V.  The adult

            A.  Physical Changes

                        1.  Appearance and structure

                                    a.  most changes after 40

                                                i.    wrinkles, graying and thinning hair, changes in weight (loss in

                                                      later life)

                                                ii.    activity level decreases (impacted by age, education, personal


                                    b.  osteoporosis-- disease resulting in loss of bone mass

                                                i.  female, small stature, smokers at risk

                                                ii. calcium and exercise beneficial

                                    c.  osteoarthritis-- aging of the joints due to use resulting in pain and

                                         restricted movement

                        2.  Functioning and health

                                    a.  decreases in physical function in all areas with time

                                                i.    loss most prominent in later life

                                                ii.    large individual differences in physiological function

                                    b.  decrease in reserve capacity-- ability of organs to respond to demand

                                                lower maximal heart rate

                                    c.  most over 70 have some chronic impairment

                        3.  Psychological implications

                                    a.  stereotypes can lead to “ageism”-- prejudice against elderly

                                                i.    many old individuals do not see themselves as old (Hurd, 1999)

                                                ii.    stereotype of “old” as inactive and solitary

                                    b.  most older individuals retain sense of well-being and

                                         function independently

            B.  The Reproductive System

                        1.  Hormones levels fluctuate (especially monthly in females)

                                    premenstrual syndrome (PMS) with symptoms of bloating, moodiness,

                                    and headaches occur in some women

                                                i.    some question validity of PMS, may be impacted by

                                                      expectation as much as hormones

                                                ii.    severe PMS may be due to hormone levels

                                                iii.   genetic and social factors influence premenstrual and menstrual


                        2.  Female menopause

                                    a.  menopause-- ending of menstrual period in midlife (i.e., no ovulation or


                                                i.    due to drop in hormone levels

                                                ii.    age of menopause somewhat related to when mom reached


                                                iii.   physical effects include hot flashes (sudden sensation of


                                                      and sweating) and vaginal dryness

                                                iv.   psychological effects vary greatly and  most women do not

                                                      experience significant psychological problems

                                    b.  hormone replacement therapy (estrogen/progestin) used to compensate

                                         for loss of hormones

                                                i.    HRT may increase risk of heart attack, stroke, or cancer

                                                ii.    short-term HRT may be used

                        3.  Male andropause

                                    a.  andropause-- male loss of reproductive capacity (“male menopause”)

                                                i.    decreased levels of testosterone

                                                ii.    less active sperm (but still capable of having children)

                                    b.  erectile dysfunction often the result of medical conditions

                                                males changes more gradual and variable

            C.  Physical Behavior

                        1.  Slowing down

                                    a.  nervous system and motor behavior decline with age

                                    b.  difficulty with balance

                                                many compensate for balance problem by walking slower

                                    c.  motor actions performed more slowly

                                                i.    may be the result of brain changes

                                                ii.    biggest impact on fine motor tasks

                                                iii.   fitness may impact speed

                                                iv.   can compensate so performance on familiar task is not as

                                                      negatively effected

                        2.  Disease, disuse, and abuse

                                    a.  effects of aging confounded with effects of disease, disuse or abuse

                                    b.  aging in absence of disease little effect on physical and psychological


                                    c.  disuse contributes to steep declines in physical functioning

                                                body and brain both need use

                                    d.  abuse of body (high fat diet, smoking) contributes to aging