Chapter5Shaffer

The Physical Self: Development of the Brain, the Body, and Motor Skills: 

The Physical Self: Development of the Brain, the Body, and Motor Skills Chapter 5 Dr. Pelaez

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Changes in Height and Weight Babies grow very rapidly during the first 2 years Doubling their birth weight by 4 to 6 months Tripling their weight by the end of the first year From age 2 until puberty children gain about 2 to 3 inches in height and 6 to 7 pounds in weight each year Physical growth and development are obvious at puberty, when adolescents enter a 2 to 3 year “growth spurt” Full adult stature is attained in the mid to late teens

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Changes in Body Proportions Newborn’s head in already 70% of its eventual adult size and represents ¼ of total body length, the same fraction of the legs Developmental proceeds in a cephalocaudal direction It is the trunk that grows faster during the first year While children grow upward, they are also growing outward according to a proximodistal formula Throughout infancy and childhood, the arms and legs continue to grow faster then the hands and feet

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Skeletal Development The skeletal structures that form during the prenatal period are initially soft cartilage that will gradually harden into bony material Skull bones are separated by six soft spots, or fontanelles, that are gradually filled in by minerals to form a single skull by age 2 Skeletal age research has been used to determine that girls mature faster then boys At birth girls are only 4 to 6 weeks ahead of boys in skeletal maturity By age 12 the gender “maturation gap” has widened to 2 full years

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Muscular Development Neonates are born with all the muscle fibers they will ever have At birth, muscle tissue is 35% water, and it accounts for no more than 18 to 24% of a baby’s body weight Muscle fibers soon begin to grow as the cellular fluid in muscle tissue is bolstered by the addition of protein and salts Muscular development proceeds in cephalocaudal and proximodistal directions

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Muscular Development Maturation of muscle tissues occurs very gradually during childhood and then accelerated during early adolescence By the mid twenties, skeletal muscle accounts for 40% of the body weight for a man and 24% of the body weight for a female

An Overview of Maturation & Growth: 

An Overview of Maturation & Growth Variations in Physical Development Individual Variations Not only is the development of body systems an uneven process, but there are sizable individual variations in the rates at which individuals grow Cultural Variations There are meaningful cultural and subcultural variations in physical growth and development People from Asia, South America, and Africa tend to be smaller than North Americans, northern Europeans, and Australians Asian American and African American children tend to mature faster than European American and European children

Development of Brain: 

Development of Brain The last 3 prenatal months and the first 2 years after birth have been termed the period of the brain growth spurt because more than half of one’s adult brain weight is added at this time Between the seventh prenatal month and a child’s first birthday, the brain increased in weight by about 1.7 grams per day, or more than a milligram per minute

Development of Brain: 

Development of Brain Neural Development and Plasticity The human brain and nervous system consists of more than a trillion highly specialized cells that work together to transmit electrical and chemical signals across many trillions of synapses All the neurons a person will ever have- some 100 to 200 billion of them- have already formed by the end of the second trimester of pregnancy, before the brain growth spurt has every begun The major contributor of the brain growth spurt is the development of a second type of nerve cell, called glia It nourishes the neurons and eventually encases them in insulting sheaths of a waxy substance called myelin The brain shows plasticity up until puberty

Development of Brain: 

Development of Brain Cell Differentiation and Synaptogenesis Influenced by the sites to which they migrate, neurons assume specialized functions Cells of the visual and auditory areas The process of synaptogenesis proceeds rapidly during the brain growth spurt The average infant has far more neurons and neural connections than adults do Neurons that successfully interconnect with other neurons crowd out those that don’t, so that half the neurons produced early in life also die early in life This reflects the remarkable plasticity of the young infant’s brain The fact that its cells are highly responsive to the effects of experience

Development of Brain: 

Development of Brain Brain Differentiation and Growth Myelinization is the process by which neurons are enclosed in waxy myelin sheaths that facilitate the transmission of neural impulses The myelin sheath acts like an insulator to speed the transmission of neural impulses, thus allowing the brain to communicate more efficiently with different parts of the body Myelinization of the higher brain centers may increase adolescent attention span and explain why they process information faster than elementary school children

Development of Brain: 

Development of Brain Cerebral Lateralization It is the specialization of brain functions in the left and the right cerebral hemispheres The highest brain center, the cerebrum, consists of two halves connected by a band of fibers called the corpus callosum. Each of the hemispheres is covered by a cerebral cortex Left cerebral hemisphere- controls the right side of the body, it contains centers for speech, hearing, verbal memory, decision making, language processing, and expression of positive emotions Right cerebral hemisphere- controls the left side of the body and contains centers for processing visual-spatial information, nonlinguistic sounds such as music, tactile sensations, and expressing negative emotions

Motor Development: 

Motor Development Investigators who have charted motor development over the first 2 years of life find that motor skills evolve in a definite sequence Infants who are quick to proceed through this motor sequence are not necessarily any brighter or otherwise advantaged, compared with those whose rates of motor development are average of slightly below average Therefore, a child’s rate of motor development tells us very little about future developmental outcomes

Motor Development: 

Motor Development Basic Trends in Locomotor Development Motor development proceeds in a cephalocaudal directions Activities involving the head, neck, and upper extremities precede those involving the legs and lower extremities The Maturation viewpoint describes motor development as the unfolding of a genetically programmed sequence of events which the nerves and muscles mature in a downward and outward direction The Experiential Hypothesis believe that opportunities to practice motor skills are also very important The Motor Skills as Dynamic, Goal-Directed Systems views motor skills as active reorganizations of previously mastered capabilities that are undertaken to find more effective ways of exploring the environment or satisfying other objectives

Motor Development: 

Motor Development Fine Motor Development Development of Voluntary Reaching An infant’s ability to reach out and manipulate objects changes dramatically over the first year. Newborns are equipped with a grasping reflex By 2 months of age, infants’ reaching and grasping skills may seem to deteriorate Reflexive palmer grasp disappears and prereaching occurs much less often These apparent regressions set the stage for the appearance of voluntary reaching Achieving motor skills at different stages can help foster perceptual development and self-esteem.

Motor Development: 

Motor Development Fine Motor Development Development of Manipulatory Skills In 4 to 6 months of age the ulnar grasp emerges, which is when an infant grasps objects by pressing the fingers against the palm The next major step in the growth and hand skills occurs near the end of the first year as infants use their thumbs and forefingers to lift and explore objects The pincer grasp transforms the child into a skillful manipulator who may soon begin to capture crawling bugs and to turn knobs, dials, etc.

Motor Development: 

Motor Development Beyond Infancy: Motor Development in Childhood and Adolescence Boys and girls are nearly equal in physical abilities until puberty Boys continue to make gains on tests of large-muscles activities, whereas girls level off or decline Biological development does not account for all the differences in large muscle performance between boys and girls Nor does it explain the declining performance of many girls, who continue to grow taller and heavier between ages 12 and 17

Puberty: The Physical Transition from Child to Adult: 

Puberty: The Physical Transition from Child to Adult The Adolescent Growth Spurt This is the rapid increase in physical growth that marks the beginning of adolescence Girls typically enter the growth spurt by age 10.5, reach their peak growth by age 12, and return to a slower rate of growth by age 13 to 13.5 Boys lag behind girls by 2 to 3 years Typically begin their growth spurt by age 13, peak at age 14, and return to a more gradual rate of growth by age 16 In addition to growing taller and heavier, the body assumes an adultlike appearance during the adolescent growth spurt Widening of hips for girls Broadening of shoulders for boys

Puberty: The Physical Transition from Child to Adult: 

Puberty: The Physical Transition from Child to Adult Sexual Maturation Sexual Development in Girls Maturation begins about age 9 or 10 as fatty tissues accumulate about their nipples and pubic hair begins to appear a little later As a girl enters her height spurt, the breasts grow rapidly and the sex organs begin to mature At about age 12.5, the average girl in Western societies reaches monarche

Puberty: The Physical Transition from Child to Adult: 

Puberty: The Physical Transition from Child to Adult Sexual Maturation Sexual Development in Boys Sexual maturation begins at about age 11 or 12 with an enlargement of the testes, which is accompanied with unpigmented pubic hair By the time the penis is fully developed at age 14.5 to 15, most boys will have reached puberty and are now capable of fathering a child Later boys begin to sprout facial hair and their voice lowers

The Psychological Impacts of Puberty: 

The Psychological Impacts of Puberty General Reactions to Physical Changes Girls typically become quite concerned about their appearance and worry about how other people will respond to them Few girls today are traumatized by menarche, but at the same time, few are overjoyed about becoming a woman Boys’ body images are more positive than those of girls, and they are much more likely than girls to welcome their weight gains Teenage boys hope to be tall, hairy, and handsome, and may become preoccupied with the aspects of body image that center on physical and athletic prowess

The Psychological Impacts of Puberty: 

The Psychological Impacts of Puberty Social Impacts of Pubertal Changes Rites of Passage Many societies (nonindustrialized) view pubertal changes as a sign and rituals are conducted that the child is becoming an adult In some other societies, the mark of puberty causes conflicts amongst child and parent

The Psychological Impacts of Puberty: 

The Psychological Impacts of Puberty Does Timing of Puberty Matter? Puberty does have some meaningful implications, although its impact differs somewhat for boys and girls Possible impacts on boys Research suggests that boys who mature early enjoy a number of social advantages over boys who mature late Possible impacts on girls Maturing early may be somewhat of a disadvantage Findings suggest that early-maturing girls are somewhat less outgoing and less popular than their prepubertal classmates

The Psychological Impacts of Puberty: 

The Psychological Impacts of Puberty Adolescent Sexuality Cultural Influences on Sexuality Societies clearly differ in the education they provide children about sexual matters and in their attempts to prepare them for their roles as mature sexual beings Sexual Attitudes and Behavior Adolescents now firmly believe that premarital sex with affection is acceptable, although, like teens of earlier eras, they think that casual or exploitative sex is wrong A second major change in teenage attitudes about sex is the decline of the double standard Sexual attitudes today are highly variable and seem to reflect an increased confusion about sexual norms

The Psychological Impacts of Puberty: 

The Psychological Impacts of Puberty Personal and Social Consequences of Adolescent Sexual Activity Changes in hormones during puberty cause an increase in sex drive (libido) and the responsibility of managing your sexuality Sexually Transmitted Disease In the U.S., one in five sexually active adolescents contracts a sexually transmitted disease (STD) Teenage Pregnancy and Childbearing Each year in the U.S., more than one million unmarried teenage girls become pregnant The consequences are likely to include an interrupted education, loss of contact with her social network, and if she is one of the 50% who drop out of school, a future of low-paying jobs that perpetuates her economic disadvantage

Causes and Correlates of Physical Development: 

Causes and Correlates of Physical Development Biological Mechanisms Effects of Individual Genotypes Unique combination of genes influence our physical growth and development Hormonal Influences- The Endocrinology of Growth By the fourth prenatal month, the thyroid gland has formed and begins to produce thyroxine The most critical of the endocrine glands is the pituitary, a “master gland”, located at the base of the brain that triggers the release of hormones from all other endocrine glands The pituitary produces a growth hormone that stimulates the rapid growth and development of body cells

Causes and Correlates of Physical Development: 

Causes and Correlates of Physical Development Environmental Influences Nutrition Diet is perhaps the most potent environmental influence on human growth and development Adequate nutrition, in the form of total calories, protein, and vitamins and minerals is necessary for children to reach their growth potentials The three growth-retarding diseases that stem from under nutrition are: Marasmus, Kwashiorkor, and Iron Deficiency Anemia The most immediate effect of over nutrition is that children may become obese and face added risk of diabetes, high blood pressure, and heart, liver, and kidney disease

Causes and Correlates of Physical Development: 

Causes and Correlates of Physical Development Emotional Stress and Lack of Affection Nonorganic Failure to Thrive An infant growth disorder, caused by lack of attention and affection, that causes growth to slow dramatically and stop Deprivation Dwarfism A childhood growth disorder that is triggered by emotional deprivation and characterized by decreased production of growth hormone (GH), slow growth, and small stature