Lecture3 psych125 bunge
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The human brain develops rapidly during prenatal development. It takes years after birth to fully mature. During the first month, the neural tube forms from the ectodermal germ layer and begins to regionalize into the brain and spinal cord. By 9 weeks, the major divisions of the brain are visible. Throughout prenatal development, the brain grows in size and complexity, with folding of the cortex and development of neural connections. Full term birth is considered 40 weeks after conception. Most abortions occur in the first trimester, before 12 weeks of gestation. Women under 25 obtain about half of all abortions in the United States.
Lecture3 psych125 bunge
- 1. PSYCH 125, Lecture 3 Functional Brain Anatomy & Prenatal Development
- 2. Question for discussion in section The human brain takes years to mature, consumes 30% of the body’s energy, and has gotten so large that unassisted childbirth is dangerous. What important function(s) does the brain serve, beyond what the spinal cord & brain stem can accomplish?
- 3. Review One way to subdivide the brain is according to anatomical features – either macroscopic ones (sulci, gyri) or microscopic ones (appearance of cells & cell layers under microscope) •What’s another way to subdivide the brain? •Which techniques can we use in humans to figure out what a brain region does?
- 4. Topographic organization in primary motor & somatosensory cortices (Penfield, 1940s-50s)
- 5. Primary visual cortex Lateral View Medial View W. W. Norton
- 6. Retinotopy in Primary Visual Cortex • injected radioactive glucose into bloodstream while monkey viewed image • “developed” brain like a photograph • Map of retina reproduced in brain! Roger Tootell et al., 1988
- 7. Visual processing Two processing streams (pathways): 1. “What”: object recognition (ventral stream = occipito-temporal) 2. “Where”: spatial localization (dorsal stream = occipito-parietal) (or “How”: how to act w/r to an object) W. W. Norton
- 8. Tonotopy in Primary Auditory Cortex
- 9. Primary, secondary, and association cortices Primary cortex Secondary cortex Association cortex W. W. Norton
- 10. Frontal cortex: Goal-directed behavior
- 11. Quiz A. B. C. Which of these lobes would play the biggest role in… •deciding which of two courses to take? •finding your way to the classroom? •remembering facts that you learned in class?
- 12. Poll What does ‘topography’ mean, in the context of the brain? A) A map of the gyri and sulci of the brain B) The spatial organization of cytoarchitectonic regions C) The fact that frequencies of sound are represented in a systematic way across primary auditory cortex D) The ordered projection of a sensory surface, like the retina or the skin, or an effector system, like the musculature, to the brain
- 13. Poll: Which box represents the sense of hearing? B A C D Primary cortex Secondary cortex Association cortex W. W. Norton
- 14. Next up Prenatal brain development 9 months http://capturedbycarrie.com/
- 16. 200-300 million sperm deposited – only 1 (if any) will fertilize the egg
- 17. That one lucky little spermatozoid
- 18. Formation of the embryo
- 19. Early stages of embryonic development Inner cell mass will Formation of the reorganize into a disk 3 germ layers
- 20. Germ layers
- 21. The Ectodermal germ layer will give rise to… • Central Nervous System • Peripheral Nervous System • Sensory epithelium of ear, nose, and eye • Skin (including hair and nails) • Pituitary, mammary and sweat glands • Enamel of teeth • Important gene for ectodermal development: Growth factor BMP4 22
- 22. Formation of the neural tube thebrain.mcgill.ca
- 23. Week 4: From neural tube to brain and spinal cord
- 24. Neural tube defects Humpath.com
- 25. Regionalization of the brain Prof. Thomas Jessell, researchchannel.org
- 26. From 1 month after fertilization through birth Prof. Thomas Jessell, researchchannel.org
- 27. Face development from 5.5 weeks to 8.5 weeks • Facial structures fuse during the 7th week • Cleft palate (1 in 500 births) develops from errors during this period
- 28. 9 weeks • Around the size of a peanut • Head is roughly half the length – bulging forehead reflects extremely rapid brain growth that has been going on for weeks
- 29. 11 weeks: major divisions of brain are visible
- 30. 16 weeks • can tell the sex of the fetus • kicking & some reflexes (breathing movements, grasping, sucking)
- 31. 18 weeks
- 32. 20 weeks • sleep/wake cycles • facial expressions (eyebrows, forehead, mouth) • head-down position more frequent
- 33. 28 weeks • eyelids flutter during REM sleep • reacts to sounds • brain waves similar to newborn • brain and lungs sufficiently developed that – if born now – could potentially survive without medical intervention.
- 34. The home stretch: 8th-9th month • Red, wrinkled skin fills out with fat (provides insulation to protect against heat loss) • Gains 1/2 lb. per week • Startle reflex is present; responds to light and sound, lifts its head • 60 percent of adult head size present36
- 35. Birth • Considered full-term if born within 10-14 days of calculated delivery date; if born earlier, considered pre-term • The earlier born, the greater the risk (due to underdevelopment) • Correlated with prematurity is low birth weight, which brings its own set of complications and risk • Normal birth weight >3500 grams • LBW <2500 grams • VLBW <2500 grams • ELBW <1000 grams 37
- 36. Milestones in prenatal development • Zygote forms after conception • Blastocyst embeds in uterine wall • Germinal stage gives rise to embryonic stage, which lasts about 8 weeks; during this time all organs, systems, etc. form • Fetal stage lasts 7 months (in full term pregnancy) and is period of elaboration and growth • Labor and delivery culmination of all this hard work – generally, 40 weeks post conception Sadler, TW (2010). Medical Embryology, Eleventh 38 38 Edition. Baltimore: Lippincott Williams & Wilkins
- 37. When do abortions occur? Percentage of 2008 Reported Abortions by Weeks of Gestation* (CDC)
- 38. Who is having abortions? • At current rates, nearly one-third of American women will have an abortion (AGI) • 50% of U.S. women obtaining abortions are younger than 25; women aged 20-24 obtain 33% of all U.S. abortions and teenagers obtain 17% (AGI). • The abortion rate of women with Medicaid coverage is three times as high as that of other women (NAF).
Editor's Notes
- #7: Monkey measurements done by labeling for radioactive glucose.
- #10: Association areas function to produce a meaningful perceptual experience of the world, enable us to interact effectively, and support abstract thinking and language.The association areas integrate information from different receptors or sensory areas and relate the information to past experiences. Then the brain makes a decision and sends nerve impulses to the motor areas to give responses. [20]
- #11: Pride & joy of the human brain. The frontal lobe or prefrontal association complex is involved in planning, controlling thoughts, actions, & emotions, as well as abstract thought.
- #14: Association areas function to produce a meaningful perceptual experience of the world, enable us to interact effectively, and support abstract thinking and language.The association areas integrate information from different receptors or sensory areas and relate the information to past experiences. Then the brain makes a decision and sends nerve impulses to the motor areas to give responses. [20]
- #15: Seminal event --- pun intended ---
- #17: Of the 200-300 million sperm normally deposited in female genital tract, only 300-500 reach site of fertilization, and generally only 1 fertilizes egg; thus, chance of fertilizing egg is roughly 1:300 million (chances of carrying zygote to term less than that)
- #18: The moment that human life begins? Depends on your beliefs.
- #25: At 4 weeks after conception, the embryo ’s tiny body is curved so tightly that the head and tail-like structure at the other end are almost touhing. The round area near the top of the head is where the eye will form the round gray area near the back of the ‘neck’ is the primordial inner ear. A primitive heart is visible – it is already beating and circulating blood. An arm bud can be seen in the side of the embryo. A leg bud is present but less distinct.
- #29: In the 5.5-week-od fetus, the nose, mouth, and palate are beginning to differentiate into separate structures. just 3 weeks later, the nose and mouth are almost fully formed.
- #30: Rudimentary eyes and ears are forming. All of the internal organs are present. Sexual differentiation has started. Fingers and toes have emerged, and nails are growing. Spontaneous movements occur, but can ’t be felt by the mother.
- #31: This picture was created by non-invasive 3-D imaging!
- #33: Sucking thumb
- #38: The weight cut-offs we use are LBW < 2500, VLBW < 1500, ELBW(extremely low birth weight) < 1000. weight in proportion to gestational age is also important. Infants who are either small or large for their gestational age are at risk for certain medical complications after birth (i.e. low blood sugar, temp instability, certain infections can affect birth weight (CMV causes low birth weight). LGA (large for gestation age) > 90%, AGA (average) 10-90%, SGA (small) <10% according to gestational age.