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Physical Growth and Development: Understanding the Body's Changes

Explore the genetic and environmental factors influencing physical growth, including the endocrine system. Learn about brain development, plasticity, and the principles of growth from infancy to adolescence. Discover milestones in motor skills, reflexes, and behavior. Gain insights into the psychological implications of physical changes during adolescence. Understand how early versus late development can impact individuals.

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Physical Growth and Development: Understanding the Body's Changes

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  1. Chapter 5The Physical Self

  2. Chapter 5: The Physical Self • Genetic and environmental forces e.g. height • Average: female 5’4” male 5’9” • Can be affected by malnutrition • Catch-up growth possible • After illness or periods of malnutrition • More short people in cold climates • Smaller body surface for heat loss

  3. The Endocrine System • Glands that secrete hormones • Pituitary gland: the master gland • Controls all other glands • Is controlled by the hypothalamus • Produces growth hormone • Testes secrete androgens like testosterone • Ovaries secrete estrogen and progesterone

  4. Figure 5-2

  5. Plasticity • Responsiveness to experiences • Can be negative • Vulnerable to damage • Environmental deprivation • Can be positive • Aids in recovery from from injury • Can compensate for each other • Can benefit from stimulation • Allows for adaptability

  6. Brain Development 2 • Critical period: late prenatal & early infancy • Lateralization (at birth) • Left hemisphere • Analytic reasoning, language • Right hemisphere • Understanding spatial information • Visual-motor information • Corpus callosum connects the two

  7. Brain Development 3 • Never truly complete • Changes occur across lifespan • Growth spurts in infancy, childhood and adolescence • Full adult weight by about age 16 • Processing speed increases in adolescence • Myelination continues into adulthood

  8. BrainDevelopment4 • The Aging Brain • Gradual and mild degeneration • Elderly adults • 5-30% fewer neurons than younger adult • Greater loss in sensory-motor areas • Plasticity still possible • Main result of age is slower processing

  9. Principles of Growth • Procession of growth is orderly • Cephalocaudal: from head, downward • Proximodistal: from the center, outwards • Orthogenic: from global, undifferentiated to specialized

  10. The Infant • Typically 7 to 71/2 lbs., 20 inches long • Period of rapid growth • Neonatal reflexes (see Table 5.3 in text) • Survival reflexes: clearly adaptive • Breathing, eye-blink,sucking/rooting • Primitive reflexes: less adaptive • Typically disappear by 4 months • Babinski: toes fan • Grasping • Used diagnostically

  11. The Infant 2 • Behavioral States • Short sleep-wake cycles at first • Establish more regularity at 3-6 months • REM sleep • 50% of the time for newborns • 25-30% by 6 months • May be useful for reducing stimulation • Individuality in infant patterns

  12. TheInfant3 • Strengths and weaknesses • Sensory system in tact • Ability to learn from experience and from consequences • Limited in capacity to move voluntarily • Intentionality also limited • Cannot interpret complex stimuli

  13. Infant Physical Behavior • Developmental norms (see Table 5.5 ) • Average age of mastery • Gross before fine motor skills • Crawling at 7–10 months • Walking at about 1 year • Study of “walkers” (Siegel & Burton, 1999) • Infants not using walkers sat up, crawled, and walked earlier • Need sensory feedback I.e.,to see feet

  14. Physical Behavior 2 • Manipulating Objects • Grasping reflex disappears: 2-4 mo • Pincer grasp by 6 months • Motor Skills • Rhythmic Stereotypies • Rocking, bouncing, mouthing objects, banging arms and legs • Precede a skill then disappear

  15. Dynamic Systems Approach • A self-organizing process • Trying new movements • Use sensory feedback • Motor milestones are learned • Also require maturation • A nature/nurture position

  16. The Child • Age 2 until puberty • 2-3 inches in height, 5-6 lbs weight • Bones grow and harden • Run faster, jump higher, and throw a ball farther • Skills very responsive to practice • Hand-eye coordination, fine motor, and reaction time all improve

  17. Adolescence • Growth spurt triggered by hormones • Peak in height: age 12/girls, 14/boys • Menarche: average age 12 1/2 • Earlier in countries with good nutrition, longer life, and higher literacy rates • Maturation different by ethnicity • AA and MA girls earlier than White • Semenarche: average age 13 • emission of seminal fluid

  18. Rates of Development • Genes set the process in motion • Hormones responsible for changes • Environment also • Secular trend: better nutrition • Earlier maturation,larger body size • Poorly nourished/mature later • Heavy & tall/mature earlier • Regular strenuous exercise/later

  19. Figure 5.6

  20. Psychological Implications • Girls become concerned w/appearance • Individual reactions vary widely • Negative views about menstruation • May contribute to poor body images • Boys likely to welcome the changes • Family relations remain important • Distance & conflict with parents • Usually about only minor issues

  21. Early vs. Late Development • Early/males: advantage • More positive reactions from others • Late/males: disadvantage • More behavior & adjustment problems • Early/females: disadvantage • Subject of ridicule,lower self esteem • Older peer group = problems • Late/ females: academic advantages • Differences tend to fade with time

  22. Physical Behavior • Dramatic physical growth overall • Boys continue to improve • Girls tend to level off or decline • Not totally explained by biology • Gender role socialization important • Gender performance gap has narrowed • E.g., track, swimming, cycling records

  23. The Adult • Minor changes in the 20s & 30s • Noticeable by the 40s • Wrinkles, gray hair, weight gain • In the 60s: Weight, muscle, bone loss • Osteoporosis in older women • Fair, light frame, smokers • Calcium, exercise, HRT • Osteoarthritis: joint deterioration

  24. Functioning and Health • Most systems show decline with age • Heart & lung capacity • Temperature control • Immune system and strength • Reserve capacity • *On average, older people are less fit than younger BUT not all • Physically active remain fit

  25. The Reproductive System • Beginning in adolescence • Sex hormones influence behavior • Males/testosterone • Levels fluctuate daily • Females/ estrogen & progesterone • monthly cycle • PMS? Expectations vs. hormones • Calcium & Vitamin D helpful

  26. Menopause and Andropause • Menopause: estrogen production declines • age range 45-54 • Symptoms: hot flashes, vaginal dryness • Little anxiety, irritability, depression, or other stereotypes • Exercise & adequate sleep helpful • Andropause: decreasing testosterone • Symptoms: Libido, fatigue, erection, and memory problems

  27. Slowing Down • Balance difficulty affects the ability to walk, stand, sit, and turn • Older people with strong muscles and good cardiovascular capacity can walk briskly • Central change is slowing in the CNS • Increased RT • Novel/complex tasks more difficult • *physically fit older people have quicker RT

  28. Disease, Disuse, and Abuse • Birren (1963) study of men aged 65-91 • Healthy older same as younger • Conclusion: Aging itself has little effect on physical and psychological functioning • Disuse: “Use it or loose it!” • Includes mental exercise • Abuse contributes to decline • Alcohol, high-fat diet, smoking

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