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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Neuron Function Impulse is carried across synapse by neurotransmitters

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

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

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

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

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

Lateralization development left: language from roughly birth right: inconsistent research

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

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

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

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

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

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

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

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

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

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

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

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

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

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

Determinants of Motor Development Physical maturation - Nature Cross-cultural similarity Perform many behaviors without learning/practice EXNavajos & walking

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