Physical Development Biological Aging

1. Chapter 3 Physical Development & Biological Aging

2. Changes in Body Proportions Growth occurs in a cephalocaudal (head to tail) pattern The head takes up one-fourth of total body length at birth, but only one-fifth at age 2. Growth occurs in a proximodistal (near to far) pattern. The head, chest and trunk precede the limbs and extremities.

3. Body Growth in Infancy Average North American newborn weight 7 ½ pounds and is 20 inches long. Birth weight triples in one year and quadruples by the end of two years. By the second year, the child is at 1/5 of its adult weight (30 lbs.) and ½ its adult height (30 + inches). Muscle tissue increases very slowly.

4. Facts about Physical GrowthEarly Childhood Middle Childhood 2-3 inches per year 5 pounds per year Baby fat declines Posture and balance improve due to lower center of gravity. 2-3 inches per year 5 pounds per year Bones harden (skeletal age), lengthen and broaden ligaments are not yet firmly attached. Improved strength and muscle tone. Primary teeth are replaced with permanent teeth

5. Influences on Physical Growth & Health Genetics Hormones Emotional well-being Nutrition Infectious disease Childhood injuries

6. Influences on Physical Growth & Health – Pituitary Growth Hormones Growth hormone (GH) needed for development of all body tissues except CNS & genitals Thyroid-stimulating hormone (TSH) causes the thyroid gland to release thyroxine, needed for normal nerve cell development and for GH to have a full impact on body size

7. Influences on Physical Growth & Health – Emotional Well Being Psychosocial dwarfism Caused by extreme emotional deprivation Appears between 2 & 15 years of age Can interfere with the production of GH Very short stature Immature skeletal age Severe adjustment problems Can be treated

8. Body Growth and Gender Girls are shorter and lighter and have a higher ratio of body fat to muscle than boys. Children differ in the rate of physical growth. Skeletal age is the best way to estimate the child’s physical maturity. African Americans mature faster than Caucasians and girls mature faster than boys.

9. GROWTH IN ADOLESCENCE Chapter 3

10. Definition of Adolescence Transition between childhood and adulthood Physically begins with puberty Culturally defined; ends gradually with assumption of adult responsibilities Lasts nearly a decade (or more) in the U.S.; culturally exaggerated due to education

11. The Growth Spurt of Puberty Most rapid growth since infancy Average of age 9 for girls; 11 for boys Girls grow 3.5 inches/year; boys 4 inches 50% of body weight gained in adolescence Also changes in leg length and facial structure

12. Why Does Puberty Happen Earlier than it Used to? Nutrition ? – Better than in earlier times Hormones ? – Found in food supply Stress ? Fat ?

13. Stress Theory of Early Puberty Hypothalamus ? pituitary? sex glands ? produce gonadotrophins Androgens (testosterone) Estrogens (estradiol) Pituitary ? thyroid gland ? produces growth hormone Cortisol (stress hormone) may trigger early onset (pituitary activity)

14. Fat Theory of Early Puberty Weight affects the timing of menarche (106 +/- 3 pounds) Athletes and anorexics become amenorrheic Fat and leptin may also be influential

15. Early vs. Late Maturation Early maturing girls have a less positive body image They are more likely to drink, smoke, be depressed, have an eating disorder or mental disorder, date and have sex earlier, and have lower educational and occupational attainment Berkley Longitudinal Study

16. Early vs. Late Maturation Early maturing boys are leaders, athletes Late maturing boys have a more positive self-image in their 30s. Early maturers, both sexes are emotionally stressed, show academic declines Berkley Longitudinal Study

17. Body Changes in Adulthood that Are Part of Normal Aging Chapter 3

18. Physical Development in Early & Middle Adulthood Early Adulthood, peak muscle tone & joint function Middle Adulthood – gradual changes, lose height, gain weight, in 40s & 50s skin sags, wrinkles, age spots, hair thins, thicker finger- and toenails, yellow teeth

19. Changes in Middle Adulthood (continued) Sarcopenia – age-related loss of muscle mass & strength Lose 1-2% per year starting at age 50 Exercise can help to reduce this loss Also lose bone from the late 30’s; this accelerates in the 50’s

20. Changes in Middle Adulthood -Cardiovascular Cholesterol increases LDL – leads to atherosclerosis Blood Pressure increases; sharply for women at menopause Metabolic disorder – hypertension, obesity, insulin resistance, high cholesterol, low HDL, weight gain (Part of normal aging?) Weight loss & exercise help Lungs become less elastic

21. Changes in Middle Adulthood - Sexuality Climacteric – loss of fertility Menopause – ceasing of menstrual cycles (average age 52) Drop in estrogen, hot flashes, nausea, fatigue, rapid heartbeat Gradual decline for men (no andropause)

22. BRAIN DEVELOPMENT Chapter 3

23. At birth, the brain is at about 30% of it’s adult weight. At age 2, the brain is at about 70% of its adult weight. Brain reaches 90% of adult weight by age 6 Brain Development

24. Prenatal : neurogenesis – 2nd trimester, fetal period Post Natal (after birth) (cycle) Synaptogenesis – dendrite formation Synaptic pruning Myelination Brain Development

25. Synaptic Transmission

26. The human brain has 100 – 200 billion neurons at birth. During the first two years, fibers from these form synaptic connections at a rapid rate and some neurons die as a result. Brain Development - Synaptogenesis

27. Experience determines brain development. Neurons not stimulated lose their synaptic connections. Neurons often stimulated strengthen connections by growth of new dendrites Brain Development – Synaptic Pruning

28. Brain Development – Glial Cells and Myelination Glial cells multiply rapidly during the first two years. (About half the brain’s volume) Glial cells produce myelin to coat neuron axons. Myelination improves the efficiency of neural transmission.

29. Cerebral Cortex The order in which cortical regions develop corresponds to the order in which capacities emerge in the growing child.

30. Cerebral Cortex In the first year, there is a burst of synaptic growth in the auditory and visual areas. Areas supporting language show dramatic growth during toddlerhood. One of the last regions to develop are the frontal lobes.

31. Brain Development Rapid frontal lobe growth at ages 3-6 Myelination of cerebellum-cortex links, reticular formation, corpus callosum

32. Specialization of functions in the two hemispheres of the cortex is called lateralization. For most people, language, logic and positive emotion are processed by the left hemisphere. Spatial and wholistic tasks and negative emotions are right hemisphere. Lateralization is very plastic. Cerebral Cortex – Lateralization & Plasticity

33. Brain growth spurts, as measured by weight, size and EEG, occur: 3 to 4- months – reach for objects 8 months – crawl, search for objects 12 months – walk 1.5 -2 years – talk Ages 9, 12, 15, 18-20 Brain Development – Sensitive Periods

34. Results in deficits in: Concentration Attention Anger and other impulse control Brain Development - Understimulation

35. Does not result in geniuses. May cause infant withdrawal. May lead to disappointed parents. May cause strain between infants and parents. Brain Development - Overstimulation

36. Brain Development in Adolescence Reward and pleasure centers (limbic system) mature before judgment centers (pre-frontal cortex) do. Baird & others (1999) found that 10-18 year olds process emotional information using the amygdala, 20-40 year olds use the frontal lobe.

37. Brain Changes in Adulthood Production of new neurons throughout life Growing new dendrites through the 70’s Brains rewire themselves – functional plasticity Myelination between cortex & limbic system in 40’s & 50’s Decrease in lateralization

38. Mankato Nun Study Early-life idea density at 22 linked to fewer incidences of mild cognitive impairment Positive emotions linked to longevity Teachers showed more moderate intellectual declines Sisters with high folic acid levels showed little Alzheimer-like damage

39. Theories of Aging Chapter 3

40. Biological Theories of Aging Cellular clock (Hayflick) 70-80 cell divisions, based on telomeres 120-year lifespan Free-radical Calorie restriction antioxidants

41. Biological Theories of Aging Mitochondrial Cellular energy producers Linked to free radical theory Hormonal Stress hypothalamic-pituitary-adrenal axis Stress & decline in immune function