lecture 3 psych 302

The role of hormones hormones play a crucial role in

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Unformatted text preview: ally mammals. The Role of Hormones   Hormones play a crucial role in sexual differentiation. -all human fetuses can develop either male or female genitalia, depending on the presence or absence of test   One of the many ways in which the fetus acts as an instigator of its own development. C. Early Development   By the 4th day after conception, the zygote arranges itself into a hollow sphere of cells with a bulge of cells, the inner cell mass, on one side. 4 5/20/13 Twins   Identical twins -originate from the splitting in half of the inner cell mass, resulting in the development of genetically identical individuals   Fraternal twins -2 eggs are released into the fallopian tube at the same time and are fertilzied by different sperm The Embryo   After implantation, the inner cell mass becomes the embryo and the rest of the cells develop into its support system. -the neural tube is a U-shaped groove formed from the top layer of differentiated cells in the embryo -it eventually becomes the brain and the SC The Embryo   The support system includes:     Placenta: permits the exchange of materials btwn the bloodstream of the fetus and that of the mother Umbilical cord: the tube that contains the blood vessesl that travel from the placenta to the developing organism and back again 5 5/20/13 Protecting the Fetus   The placental membrane is a barrier against some, but not all toxins and infectious agents.   The amniotic sac, a membrane filled with fluid in which the fetus floats D. Fetal Behavior   By 12 weeks after gestation, most of the movements that will be present at birth have appeared.   Prenatal to postnatal continuity   Swallowing amniotic fluid promotes the normal development of the palate   Movement of the chest wall and pulling in and expelling small amounts of amniotic fluid Behavioral Cycles   Become stable during the second half of pregnancy   Circadian rhythms are also apparent -near the end of pregnancy, the fetus's sleep and wake states are similar to those of the newborn 6 5/20/13 E. Fetal Experience   The sensory structures are present relatively early in prenatal development and play a vital role in fetal development and learning. -prenatal visual experience is negligible -fetus experiences tactile stimulation as a result of its own activity, and tastes and smells the amniotic fluid -it responds to sounds from at least the 6th...
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