Chapter 3 - Grade: 100 PDF

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I.

Growth in Infancy a. In infancy, growth is so rapid and the consequences of neglect are so severe that gains are closely monitored. b. Length, weight, and head circumference should be measured monthly at first, and every organ should be checked to make sure it functions well. c. Body Size i. Weight gain is dramatic. ii. Newborns lose weight in the first three days and then gain an ounce a day for several months. iii. Birthweight typically doubles by 4 months and triples by a year. iv. Physical growth in the second year is slower but still rapid. 1. By 24 months, most children weigh almost 28 pounds. a. They have added more than a foot in height – from about 20 inches at birth to about 34 inches at age 2. i. This makes 2-yesr-olds about half their adult height and about one-fifth their adult weight. v. Each of these numbers is a norm, which is a standard, for a particular population. 1. These numbers are norms for North America. vi. At each well-baby checkup, the baby’s growth is compared to that baby’s previous numbers. 1. Often measurements are expressed as a percentile, from 0 to 100, comparing each baby to others the same age. vii. For any baby, an early sign of trouble occurs when percentile changes markedly either up or down. d. Sleep i. Throughout life, health and growth correlate with regular and ample sleep. 1. As with many health habits, sleep patterns begin in the first year. ii. Newborns sleep about 15 to 17 hours a day. 1. Every week brings a few more waking minutes. a. For the first two months the norm for total time asleep is 14 ¼ hours; for the next 3 months, 13 ¼ hours; for the next 12 months, 12 ¾ hours. i. Remember that norms are averages; individuals vary. iii. Infants also vary in how long they sleep at a stretch. 1. Preterm and breast-fed babies wake up often. a. Part of this depends on an adult’s perspective. iv. Over the first moths, the time spent in each type or stage of sleep changes. 1. Babies born preterm may always seem to be dozing. a. About half the sleep of full-term newborns is REM (rapid eye movement) sleep, with flickering eyelids and rapid brain waves.

i. That indicates dreaming. b. REM sleep declines over the early weeks, as does “transitional sleep,” the half-awake stage. i. At 3 or 4 months, quiet sleep (also called slow-wave sleep) increases markedly. v. Sleep varies not only because of biology (age and genes) but also because of culture and caregivers. 1. Babies who are fed formula and cereal sleep longer and more soundly – easier for the parents but not necessarily good for the baby. 2. Where babies sleep depends primarily on the baby’s age and the culture, with bed-sharing (in the parent’s bed) and co-sleeping (in the parents’ room) the norm in some cultures, but unusual in others. vi. Parents are soon frustrated if they think their babies will adjust to adult sleep-wake schedules. 1. Infant brain patterns and hunger needs do not allow them to sleep quietly for long stretches. a. This can create a problem for the entire family. e. Brain Development i. Prenatal and postnatal brain growth (measured by head circumference) is crucial for later cognition. ii. From two weeks after conception to two years after birth, the brain grows more rapidly than any other organ, being about 25 percent of adult weight at birth and almost 75 percent at age 2. 1. Over the same two years, brain circumference increases from about 14 to 19 inches. iii. If teething or a stuffed-up nose temporarily slows weight gain, nature protects the brain, a phenomenon called head-sparing. 1. Sadly, head-sparing does not last forever: Prolonged malnutrition affects the brain. iv. Brain Basics 1. Communication within the central nervous system 0 the brain and spinal cord – begins with nerve cells, called neurons. a. At birth, the human brain has an estimated 86 billion neurons. 2. The final part of the brain to mature is the prefrontal cortex, the area behinds the forehead that is crucial for anticipation, planning, and impulse control. a. The prefrontal cortex is inactive in early infancy and gradually becomes more efficient in childhood, adolescence, and adulthood, with marked variation from one person to another at every age.

3. Neurons connect to other neurons via intricate networks of nerve fibers called axons and dendrites. a. Each neuron typically has a single axon and numerous dendrites, which spread out like the branches of a tree. 4. The axon of each neuron reaches toward the dendrites of other neurons at intersections called synapses, which are critical communication links between the brain.b 5. Axon and dendrites do not touch at synapses. a. Instead, the electrical impulses in axons cause the release of chemicals called neurotransmitters, which carry information from the axon of the sending neuron to the dendrites of the receiving neuron. v. Growth and Pruning 1. During the first months and years, rapid growth and refinement in axons, dendrites, and synapses occur, especially in the cortex. a. Dendrite growth is the main reason that brain weight triples from birth to age 2. i. An estimated fivefold increase in dendrites in the cortex occurs in the 24 months after birth, with about 100 trillion synapses present at age 2. 2. Every dendrite growth is called transient exuberance; exuberant because it is rapid and transient because some is temporary. a. This expansive growth is followed by pruning. This is where unused brain connections atrophy and disappear. b. Pruning is beneficial. 3. Experiences sculpt the brain. a. Some sculpting is called experience-expectant and some is called experience-dependent. i. Brain development is experience-expectant when it must happen for normal brain maturation to occur. 1. Because they are basic to human development, expectant experiences occur for almost every baby. 2. Without such expected experiences, dendrite and specific regions of the brain do not grow. ii. Certain facets of brain development are experiencedependant: They result from experiences that differ from one baby to another, resulting in brains that also differ. vi. Implications for Caregivers 1. Severe lack of stimulation stunts the brain. vii. The Senses

1. Sensation occurs when a sensory system detects a stimulus. 2. Perception occurs when the brain processes a sensation. 3. Hearing a. The fetus hears during the last trimester of pregnancy; loud sounds trigger reflexes even without conscious perception....