Chapter 6 – Physical Development

1. Chapter 6 – Physical Development I. Growth Patterns Top down - cephalocaudal - head develops first - vital functions first (survival)

2. Center outward – proximodistal - internal organs first - trunk faster than arms & legs - BUT in adolescence, hands & feet fastest (awkward)

3. II. Phases of growth Infancy/early childhood (0-5) • Rapid growth • Nervous system • Body size

4. Middle/late childhood (6-12) • Slower growth • 2" & 6 lbs/year Adolescence (13-20) • Rapid growth • Body size (3-6" & 10-15 lbs) • Reproductive system

5. Puberty: • girls: breast enlargement, growth spurt • boys: testicle enlargement Individual variability

6. Population trends 1. Bigger & heavier 100 years ago man = 5'7" woman= 5'3" Today: man = 5'9" woman = 5'4"

7. 2. Growth is earlier • Average age for menarche - 100 years ago = 15 - today = 13 3. Industrialized vs. 3rd-world • Better medical care • Nutrition

8. III. Environmental Effects on Growth A. Nutrition Provides energy - Basic body functions - Physical activity - Growth, especially after birth

9. Special needs of infants - higher proportion of calories - more vitamins & minerals

10. Malnutrition (50% of kids) - failure to grow normally - delayed & smaller growth spurt - critical period of 1-3

11. Nutritional diseases Marasmus - inadequate calories - in 1st year - from malnourished mother - infant can die

12. Kwashiorkor - inadequate protein - ok while breast-fed -> years 1-3

13. childhood illnesses - weakened immune system -> smaller, lower IQ, etc.

14. Over-nutrition - heredity + environment - physical illness - social problems

15. B. Climate Body types adapted to climates east Africans vs. northern Asians Seasonal variations in growth - grow faster in spring & summer

16. C. Psychosocial Effects 1. Emotional stress - “Failure to thrive” - emotional traumas reduce growth hormone - some catch up

17. 2. Popularity & timing of puberty Boys - early maturation = better during adolescence - late-maturing boys benefit later; more sensitive & flexible

18. Girls - mixed results in girls - disadvantages to early maturation - but differences disappear

19. II. Central Nervous System (CNS) • CNS = Brain & spinal cord

20. Neuron Structure • Cell body - nucleus • Dendrites - receive information • Axon - sends information • Myelin sheath - conductance

21. Neuron Function • Impulse is carried across synapse by neurotransmitters

22. Brain structures & functions Cerebrum/cortex • Higher functions • 2 hemispheres (separated by corpus callosum) • Left = language • Right = visual-spatial, humor, perceiving emotions

23. 4 Lobes • Frontal - personality, executive, motor • Parietal - speech, sensory • Occipital - vision • Temporal - hearing

24. Subcortex Limbic system - emotions, pleasure & aversion, - sensory & motor impulses Reticular formation - sleep & wake

25. Cerebellum • Involuntary motor • Body equilibrium & muscle tone Medulla • Reflexes Spinal cord • Impulse conduction to body parts

26. Brain Development Brain size • 25% of ultimate size by birth • 90% by age 5 Number of neurons • Born with total number • Grow in size & connections

27. Lateralization development • left: language from roughly birth • right: inconsistent research

28. III. Motor Development Principles 1. Gross before fine Coordination of large muscle groups before small muscle groups

29. 2. Differentiation • Learn to control specific muscles to enact specific behaviors 3. Integration • Put individual, differentiated actions together into complex movements

30. Gross Motor Control(large muscles) Control over upper body • Holds chest/head up (3 mos) Control over whole body • Sits unsupported (5 mos)

31. Gets into sitting position (7 mos • Spontaneous kicking • Alternating leg movements Pulls to standing (7-8 mos) Crawls - 10 months

32. Stands alone (11 mos) • Walks (> 1 year) • Refines walking (1-2 yrs)

33. Uses 2 feet together (2 yrs) • Full body control (6 yrs) - boys better by 12 • Cultural differences in milestones

34. Fine Motor Control(small muscles) Newborns: grasping reflex - & sometimes hand to mouth 1-2 months - decline in grasping reflex - visually-guided reaching (good by 3 months) - but touch objects only on same side of body as arm

35. 4 months • reach inward to body midline • use 2 hands simultaneously 5 months - coordinated actions with both hands

36. 7-8 months - sequence of behaviors with hands 18 months - improved finger control 8-10 years - skills close to adults

37. Handedness • 90% = right hand; 7-8% = left hand • Across cultures & 50 centuries • Preference by age 1 • Consistent by age 3

38. Reasons for Right-Handedness Environmental • R-handed world • Lefties forced to use right hand • But R-hand consistency across cultures

39. Age-Handedness Correlation: • With increase in age = fewer lefties • Because older folks forced to use R hand? • BUT - lefties die at earlier ages • Women = 5 years Men= 10 years • Safety

40. Genetic: recessive trait? • But only 35% kids of 2 lefty parents are L-handed • MZ twins not more alike than DZ twins • DZ twins not more alike than unrelated people

41. Other biological • Related L-hemisphere dominance • Unknown mechanisms • Birth-related trauma? disrupt normal hemispheric organization? - greater neurological problems & birth stress • More lefties develop Alzheimers

42. Determinants of Motor Development Physical maturation - Nature • Cross-cultural similarity • Perform many behaviors without learning/practice EX Navajos & walking

43. Learning - Nurture • Activity changes brain • Many behaviors must be practiced - Ache • Some cultural differences • Training can speed motor development Conclusion: biology + environment