Prenatal and Infant Development Mr. Koch AP Psychology Forest Lake High School

Conception A single sperm fertilizes a single ovum (egg) to create a zygote – “germinal stage” - process of rapid cell division and then differentiation – At about 10 days, attaches to wall of uterus Outer cells form placenta, inner cells develop into embryo

Embryonic Stage Stage from 2-9 wks after conception – Organs begin to form and function Develops heart, nervous system, stomach, esophagus, ovaries or testes Develop eyes, ears, nose, jaw, mouth lips By end have tiny arms w/ elbows, hands, fingers Legs have knees, ankles, toes

Fetal Stage 7 month period of prenatal development, spanning 9 weeks from conception to birth – Begins to look distinctly human – Organs grow and start to function By 3 months: can kick, make fist, turn head, open mouth, swallow, frown In 6 th month: eyelids open, has tastebuds, well-developed grasp, can breathe regularly as long as 24 hrs. at a time – Could potentially survive premature birth by end of 6 th month Organ systems typically functional by end of 7 th month 8 th & 9 th month: respond to light & touch, hear outside sounds – Can also learn – respond differently to sound of mother (faster heartbeat) and stranger (slower heartbeat)

Teratogens Potentially harmful agents (i.e. viruses, chemicals) that can affect prenatal development Placenta screens out most harmful substances, but these sneak through – Especially harmful if during embryonic stage “critical period” in prenatal development – If heart, eyes, ears, hands, feet don’t appear, cannot form later – if formed incorrectly, defects are permanent – Teratogens during fetal stage affect size, behavior, intelligence, and health

Teratogens Disease Can be born with AIDS or experience physical defects from other diseases like rubella Drugs (i.e. heroine, cocaine, crack) Can be born addicted “Crack babies” – premature, underweight, tense, fussy, delayed physical growth & motor development, behavior & learning problems Smoking/nicotine Can cause respiratory problems, irritability, social/attention problems, greater risk for nicotine addiction later in life, can harm brain development Can cause reduction of nutrients that can lead to premature and underweight birth, which can cause cognitive and behavioral problems

Teratogens Alcohol Can kill fetal brain cells – depresses fetal nervous system, putting at risk for birth defects & mental retardation – Fetal Alcohol Syndrome (FAS) Characterized by mental retardation, possible physical malformations Behavioral and psychological problems also linked to mothers experiencing significant stress, depression, or flu in first 6 months Fortunately, vast majority of infants (>90% in western nations) are born without mental or physical problems

Newborns How do we study capabilities of infants? – Very difficult – present stimuli & monitor response – Eye movements, changes in heart rates, sucking rates, brain waves, body movements, and skin conductance Can see at birth – Blurry, but able to see large, close objects » Seem to prefer faces and seem prepared to distinguish from other visual stimuli Born with limited hearing capabilities – Notice single note differences of tone, turn head toward sounds, particularly attuned to sounds of speech Similar sense of smell & taste to adults, but less developed – Breast-fed infants show preference for smell of own mother to others In general, infants’ sensory abilities seem to dispose to focus attention on caregiver

Newborns Born with numerous reflexes that aid survival – Involuntary, unlearned motor behaviors – Ex. “rooting” reflex, sucking, etc. Most disappear in 3-4 months when brain development allows voluntary control of muscles and development of motor skills

Newborns Brain development Born with overabundance of neurons, but immature (connections poorly developed) After birth, neural networks develop rapidly until puberty when “pruning” process gains importance

Newborns Brain development helps enable maturation – Natural growth or change that unfolds in a fixed sequence, relatively independent of environment – Must be biologically prepared for certain changes to develop Age of maturation will vary, but sequence rarely does However, research shows that once properly matured, experience can impact efficiency, effectiveness of development – Once again, nature and nurture interact