Chapter 5 The Physical Self

The neuron Dendrites Cell Body Axon Synapse Neurotransmitters

Figure 5-2 Parts of a neuron Figure 5-2 Parts of a neuron. (a) Although neurons differ in size and function, they all contain three main parts: the dendrites, which receive messages from adjacent neurons; the cell body; and the axon, which sends messages across the synapse to other neurons. (b) The formation of dendrites leading to new connections among existing neurons, as well as the myelination of neural pathways, accounts for much of the increase in brain weight during a baby’s first two years. Figure 5-2

Plasticity Responsiveness to experiences Can be negative Vulnerable to damage Environmental deprivation Can be positive Aids in recovery from from injury Can compensate for each other Can benefit from stimulation Allows for adaptability

Brain Development Critical period: late prenatal & early infancy Lateralization (at birth) Left hemisphere Analytic reasoning, language Right hemisphere Understanding spatial information Visual-motor information Corpus callosum connects the two

Brain Development Never truly complete Changes occur across lifespan Growth spurts in infancy, childhood and adolescence Full adult weight by about age 16 Processing speed increases in adolescence Myelination continues into adulthood

Brain Development The Aging Brain Gradual and mild degeneration Elderly adults 5-30% fewer neurons than younger adult Greater loss in sensory-motor areas Plasticity still possible Main result of age is slower processing

Principles of Growth Procession of growth is orderly Cephalocaudal: from head, downward Proximodistal: from the center, outwards Orthogenic: from global, undifferentiated to specialized

Infant Physical Behavior Developmental norms (see Table 5.5 ) Average age of mastery Gross before fine motor skills Crawling at 7–10 months Walking at about 1 year Study of “walkers” (Siegel & Burton, 1999) Infants not using walkers sat up, crawled, and walked earlier Need sensory feedback I.e.,to see feet

Physical Behavior Manipulating Objects Grasping reflex disappears: 2-4 mo Pincer grasp by 6 months Motor Skills Rhythmic Stereotypies Rocking, bouncing, mouthing objects, banging arms and legs Precede a skill then disappear

Adolescence Growth spurt triggered by hormones Peak in height: age 12/girls, 14/boys Menarche: average age 12 1/2 Earlier in countries with good nutrition, longer life, and higher literacy rates Maturation different by ethnicity AA and MA girls earlier than White Semenarche: average age 13 emission of seminal fluid

Rates of Development Genes set the process in motion Hormones responsible for changes Environment also Secular trend: better nutrition Earlier maturation,larger body size Poorly nourished/mature later Heavy & tall/mature earlier Regular strenuous exercise/later

Psychological Implications Girls become concerned w/appearance Individual reactions vary widely Negative views about menstruation May contribute to poor body images Boys likely to welcome the changes Family relations remain important Distance & conflict with parents Usually about only minor issues

Early vs. Late Development Early/males: advantage More positive reactions from others Late/males: disadvantage More behavior & adjustment problems Early/females: disadvantage Subject of ridicule,lower self esteem Older peer group = problems Late/ females: academic advantages Differences tend to fade with time

Physical Behavior Dramatic physical growth overall Boys continue to improve Girls tend to level off or decline Not totally explained by biology Gender role socialization important Gender performance gap has narrowed E.g., track, swimming, cycling records

The Adult Minor changes in the 20s & 30s Noticeable by the 40s Wrinkles, gray hair, weight gain In the 60s: Weight, muscle, bone loss Osteoporosis in older women Fair, light frame, smokers Calcium, exercise, HRT Osteoarthritis: joint deterioration

Functioning and Health Most systems show decline with age Heart & lung capacity Temperature control Immune system and strength Reserve capacity On average, older people are less fit than younger BUT not all Physically active remain fit

Slowing Down Balance difficulty affects the ability to walk, stand, sit, and turn Older people with strong muscles and good cardiovascular capacity can walk briskly Central change is slowing in the CNS Increased RT Novel/complex tasks more difficult *physically fit older people have quicker RT

Disease, Disuse, and Abuse Birren (1963) study of men aged 65-91 Healthy older same as younger Conclusion: Aging itself has little effect on physical and psychological functioning Disuse: “Use it or loose it!” Includes mental exercise Abuse contributes to decline Alcohol, high-fat diet, smoking