CH5 - Physical development Flashcards
Time infants reach half their adult size:
boys: 2 years
girls: 18 months
Features of human growth
Muscles become longer & thicker as individual fibers fuse together (boy puberty)
Layer of fat first appears under skin near end of the fetal period; continues to accumulate rapidly during the first year after birth (baby fat)
Increase in weight for high risk obesity noticeable by age 4
Bone starts as cartilage, middle of tissue turns to bone, shortly before birth ends (epiphyses) turn to bone
Secular growth trends
changes in physical development related to environmental factors through generations (normal does not equal average)
Mechanisms of physical growth
Heredity - .7 correlations between child’s height and average of both parents
Hormones - pituitary secretes growth hormone (GH) during sleep or after exercise, travels to the liver, liver releases somatomedin which causes growth of muscles & bones (dwarfism = GH deficiency)
Thyroxine released by thyroid gland allows for nerve cells to devel properly - anxiety related problems? Caused by alcohol consumption during pregnancy?(rats)
Nutrition
40% of energy devoted to growth in a 2 month old (rest to digestion, respiration) - need 100-120 cals per kg of body weight per day until 2 yrs
Malnutrition - 16.9 million children under age 5 → indistinguishable physically but lower intelligence tests & difficulty maintaining attention. Solution: food availability, nutrition education & behavioral change
Diseases - 5.9 million children under age 5 dead - birth complications, pneumonia, birth asphyxia, diarrhea, malaria (45% related to malnutrition)
Developing nervous system (neurons & axons)
Axons acquire myelin at 4 months - first sensory info, cortex last
After birth: brain grows rapidly, axons & dendrites grow longer, dendrites sprout new limbs (increasing # synapses)
Synaptic pruning = downsizing cuz of useless connection after 1st birthday
Early neuronal development
3rd week - area of ectoderm thickens and forms neural plates - neural folds form neural tube
4 weeks - bulges and bends form primary vesicles: prosencephalon (cerebrum), mesencephalon, rhombencephalon (brain stem & cerebellum)
11 weeks - resembles total structure
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Forms of neuroimaging:
EEG - electrical activity, brain waves, good temporal
fMRI - magnetic field to track blood flow
PET - traces glucose
fNIR or functional near infrared spectroscopy - measures blood flow, silent, unclear spatial image in deep brain areas
avoidance & brin structures
Left frontal cortex regulates emotions stemming from tendency to approach, right = avoidance
Motor development
fine motor skills (grasping, manipulating objects); gross-motor skills
Motor development - innate reflexes
Babinski, grasping/palmer, rooting, sucking, stepping, blinking, moro (monkey), swimming (6), tonic neck (most disappear 3-4 months months)
Dynamic systems theory (motor development)
Coordinating skills - understanding specific tasks (differentiation) to make up whole situation (integration)
Locomotion
sit upright with support (4 months), sit (7 months), stand w support (9 months), walk with assistance (14 months), climb, walk backward, kick ball (24 months)
Stepping - 10 months, by 6/7 months understands alternating steps
Posture & balance
cephalocaudal growth - use inner ear cues after a few months
Fine-motor skills
Reaching & grasping but uncoordinated (4 months), coordinated at 5 or 6 months, pick up food at 6 months, eating with spoon at 1 year (2 year olds use wrist), hand positioning & thumb use (7 or 8 months)
Sensory & perceptual processes - Smell, taste, touch
receptors are functional in the fetus and useful to newborns
Hearing
fetus can hear at 7 or 8 months, infants do not hear well as adults - higher auditory threshold (low), recognize name by 4.5 months, using sound to estimate difference by 7 months, full auditory capacity at 30 months
seeing - light, tracking moving objects
6 meters vs 60-120 m in adults & basically 1 year olds
cones
Infants respond to higher saturation levels than adults can perceive (cones in retina circuits functioning at 3 months
perceptual consistencies (seeing)
Size consistency by 4 or 5 months, most others at 4
Depth
Visual cliff - 1.5 month old notices a difference, 7 month old perceives depth (fears cliff)
7 month olds use linear perception & texture gradient
Edges
infants have 2 separate visual systems, one for perception of objects and one for interpreting visual stimuli from moving objects
1 month olds focus on edges of phase while 3 month olds focus on face features
