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PSY 118 Ch. 4

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Daniel Gaona

on 25 February 2016

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Transcript of PSY 118 Ch. 4

(forms 2 weeks after conception)
(forms 3-8 weeks after conception)
*Brain, spinal cord, eyes, heart, limbs, ears begin to form
(forms 9 weeks after conception till birth)
*Myelin begins to form at 24 weeks
REM activity can be recorded at 28 weeks
*Environmental Risks can effect at anytime of development in the womb
1st step after conception (reproductive cells combine: sperm & egg)
is formed.
Usually forms 2 weeks after conception.
Develops 3 "Germ" layers
1. Ectoderm
2. Mesoderm
3. Endoderm
: develops into nerve tissue & skin.
: develops into muscle & bone.
: develops into soft tissue (digestive organs).
is formed

3-8 weeks after conception
Heart, stomach, liver are formed
By week 4 the nervous system develops into the forebrain, midbrain, hindbrain, spinal cord
develops about 9th week after conception
Period 9-40 weeks (birth)
continued growth & develop of organ systems occur
*new neurons are generated and begin forming connections
At 6 months myelination of nervous system occurs
At 7 months REM can be recorded
REM allows fetus to refine neural connections
Fetus can hear sounds/voices outside the womb
Fetus has preferences to food mother eats
Most pregnancies last about 37 to 40 weeks
-37-42 weeks is considered full-term
usually weigh 7 lbs & 20 inches long
-12% of babies in the US are born immature before 37 weeks
-2% are born before 32 weeks
Premature births increase risk of impairments lungs, vision, & brain development
Genetic Risks to Development
Most common genetic abnormalities
are due to parents age.
Ex: Woman's eggs are formed prenatally.
Most common genetic abnormalities due to age is down syndrome
Child has 3 copies of 21st chromosome
Marked by intellectual disability, mild physical abnormality, & decreased life span.
*Risk goes up as mother ages
Genetic Abnormalities usually result in a miscarriage
New technology allows parents to screen for genetic abnormalities
Gives parents the option to abort fetus
Environmental Risks
: protects fetus from most toxins & disease

: a chemical agent/disease that can harm the zygote, embryo, fetus

Types of Teratogens include:
(premature births)
(heart defects, intellectual impairments)
(premature birth)
(fetal alcohol syndrome: small stature, facial abnormalities, cognitive impairments)
Chicken pox
(blindness, small head, seizures)
Rubella/German Measles
(blindness, heart disease)
(passed by birth, breast feeding)
Germinal Period
-1st 2 weeks of prenatal development after conception
Most dramatic & extensive transformation occurs before birth
Embryonic Period
-The Stage of prenatal development from 3rd to 8th week after conception
-Basic forms of all body structures & internal organs develop
-Day 14 to 56
-head, eyes, ears, nose &mouth appear in 4th week
-Legs, knees,
feet & webbed
toes appear a
few days later
-By 5th week buds (arms & legs appear)
Then 52-54
days after conception
fingers & toes
Fetal Period
-9th week after conception until birth
-Fetus gains about 7 pounds & organs become more mature to the point of being fully functional
By end of 3rd month sex organs are visible via ultrasound
By 4th, 5th, 6th
& buds for teeth
form, hair grows
Behavioral Teratogen:
teratogens that can harm prenatal brain impairing intellectual & emotional functioning
Threshold effect:
when a teratogen is relatively harmless in small doses but becomes harmful once exposure reaches a certain level
Dose, timing, frequency, & other teratogens affect when threshold is crossed
Teratogens can be:
: Measles, Syphillis
: Lead, Mecury
Social & Behavioral Factors
: stress, malnutrion
Medicinal drugs
: Lithium
Psychoactive drugs
: alcohol, caffeine

Ch.4 Prenatal Development
Most dramatic & extensive transformation occurs before birth
We go from 2 cells to 1 cell
to 100 trillion cells by birth
-Characterized by rapid cell division & beginning of cell
(specialization in structure & function)
Full transcript