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Child And Adolescent Development

Child and Adolescent Safety Statistics [WLOs: 1, 2, 3] [CLOs: 2, 6]

Prior to completing this discussion, please read Chapters 5 and 6 in your textbook. You may be interested in viewing the interactive infographic within Chapter 6 to learn more about specific safety statistics.

Safety is an important issue to consider when explaining the physical development in children and adolescence. For this discussion, you will address the following:

Provide examples of new safety guidelines that did not exist either when you were growing up, or when your parents were growing up.
Then, review What Is CRAAP? A Guide to Evaluating Web Sources (Links to an external site.) and search the internet for credible sources, using Ashford University Library’s video Scholarly and Popular Resources (Links to an external site.) for guidelines. Find and report on three statistics specifically related to child and adolescent safety from this current decade (2010 to present). Provide one statistic for each of the three stages: infancy or toddlerhood, childhood, and adolescence. Address the social system (family, school, and the community) that is affected by this statistic if applicable.
In other words, you will have one unique statistic for each of the three stages. Be sure to reference the site where the statistic was located.
See the example below:

One statistic found on the Centers for Disease Control and Prevention web page, under the Child Passenger Safety: Get the Facts, Risk Reduction for Every Age tab, states that, “Car seat use reduces the risk for death to infants (aged <1 year) by 71%; and to toddlers (aged 1–4 years) by 54% in passenger vehicles” (2017, para. 3).

Reference:

Centers for Disease Control and Prevention. (2017). Child passenger safety: Get the facts (Links to an external site.). Retrieved from http://www.cdc.gov/MotorVehicleSafety/Child_Passenger_Safety/CPS-Factsheet.html

Learning Objectives

After completing this module, you should be able to:

ሁ Describe changes in body and brain structure from birth through adolescence. ሁ Detail the process of nerve function and how neurons transmit signals. ሁ Provide behavioral examples that demonstrate how the brain is organized. ሁ Outline major milestones in motor development. ሁ Clarify important issues related to toilet training. ሁ Identify warning signs of various physical disabilities that may first appear in early childhood. ሁ Describe physical changes that take place during puberty, including historical and cultural trends,

and the differential impact on males and females.

Section 5.1General Patterns of Growth

Prologue Among infants and young children, tremendous changes occur in every domain of develop- ment. However, none are more apparent than the physical changes. When new parents talk about their baby’s growth, the first thing that usually comes to mind is height, weight, and motor activity. Imaging devices now allow us to track coinciding changes in brain tissue. We can conclusively differentiate between a male brain and a female brain—even at birth. Though we are far from making predictions about physical development based on brain scans, we can predict some effects of deprivation. For instance, malnutrition can have far-reaching conse- quences, extending into physical, cognitive, and even psychosocial domains.

Quite unlike other animal species, human infants are virtually helpless at birth. Babies can eat only if a nipple is provided; they cannot move objects out of the way or closer; and for the most part they cannot manipulate the physical structure of the environment. Initially they do not even have the muscle strength needed to hold up their heads. It is only with adult assistance that infants can survive and eventually optimize growth. Technology and scien- tific advancement have allowed us to better understand how we transition from completely dependent beings into adolescents who are perfectly capable of walking away from their par- ents. This module focuses on those physical developments.

5.1 General Patterns of Growth Though parents do not often notice, the heads of infants are disproportionately large com- pared to the rest of their bodies. On their way to adult proportions, the torso and limbs grow faster than the head. This pattern of growth is an example of directionality, one of the gen-

eral principles of human growth. In this case, the direction is cephalocaudal, literally meaning “head to tail.” At birth not only is the head more developed physically than the rest of the body, but also vision and hearing precede growth of the limbs. That is, babies begin to focus their eyes on what they hear well before they begin walking or perform coordinated hand movements.

Physical growth also occurs in a proximodistal pattern— from the inside out. In the prenatal environment, this prin- ciple is displayed as the spinal cord develops before fingers and toes. The pattern continues after birth, as infants learn to move their torsos before their extremities. Babies learn to use their arms to maintain balance before they use their hands and fingers to reach for an object.

Another general principle of physical growth is indepen- dence of systems. This principle suggests that different body systems grow and mature independently. As seen in Figure 5.1, the nervous system matures quite rapidly begin- ning in childhood, whereas the pattern of growth of overall stature (body size) is a bit more even. And neither the tim- ing nor the rate of sexual maturation mirrors that of either the nervous system or stature.

David De Lossy/Photodisc/Thinkstock ሁ Physical development

depends on maturation but still involves interchange with the environment.

Section 5.2Neuropsychology and Brain Development

Figure 5.1: Independence of systems ሁ This graph illustrates that different body systems grow and mature independently.

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Lymph tissue Brain and head

General growth curveGenitals

Source: Tanner, J. M. (1962) Growth At Adolescence, 2nd ed., Oxford: Blackwell Scientific Publications.

S E C T I O N R E V I E W Provide examples that demonstrate the three general patterns of growth.

5.2 Neuropsychology and Brain Development As the cephalocaudal principle implies, the brain is closer to its adult size than is any other physical structure in the newborn human. Embryonic cells have been transformed into a sophisticated machine with all kinds of specialized processes. The brain integrates informa- tion from the environment and from the body’s multiple systems. Children learn to walk, run, and hop, leading to more complex physical feats like executing studied gymnastics moves, diving into a pool, or high jumping. These changes necessarily begin with the brain and ner- vous system. In this section, we explore these developments as they relate to early physical growth. We look first at the brain from a cellular level, and then explore how the different parts of the brain communicate with each other and the rest of the body.

Neurons and Synaptic Development There are at least 100 billion neurons, or nerve cells, in the human brain. The neuron is the basic element of the nervous system, as displayed in Figure 5.2. Unlike other cells, neurons communicate with each other in an elaborate relay system. Information is first transmitted by

Section 5.2Neuropsychology and Brain Development

dendrites, structures that receive incoming signals. The message then travels to the soma (cell body). If the signal is to be continued, it travels via the axon. The transmission may be sped up by a myelin sheath, which eventually covers most of the long, threadlike axons.

The neuron transmits the impulse to the next neuron (or gland or muscle fiber) at bulblike structures called terminal but- tons. This transmission is achieved with- out the neurons actually touching each other. Instead, they form a synapse, or gap between the sending and receiving neurons. Every terminal button contains vesicles that release chemicals called neurotransmit- ters into the synapse. Depending on a num- ber of factors, especially the concentration of the specific neurotransmitter, the receiv- ing neuron will either carry the message forward or not. That is why sometimes peo- ple can perceive a faint sound or a distant light while at other times they cannot. The

chemical messengers have either reached a particular threshold to transmit the sensory mes- sage or not.

Figure 5.2: The neuron ሁ The neuron is the basic element of the nervous system. Information is first received by the

dendrites. The message travels to the cell body (soma). If the message is to be continued, it travels to the axon, where transmission may be sped up by the myelin sheath, which covers many axons. At the terminals, neurotransmitters are released into the synapse between the sending and receiving neurons.

Dendrite

Nucleus

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Courtesy of Ron Mossler ሁ Every potential visual, auditory, and tactile

stimulus sparks production of synaptic growth.

Section 5.2Neuropsychology and Brain Development

It was previously thought that we do not manufacture neurons after we are born. How- ever, recent research has confirmed that some sensory neurons continue to regenerate throughout the lifespan, and there are even indications of the growth of some neurons related to cognition. For instance, evidence indicates that neural growth can be promoted in the hippocampus, possibly slowing or reversing the effects of memory loss associated with dementia (Frielingsdorf, Simpson, Thala, & Pizzo, 2007; Ho, Hooker, Sahay, Holt, & Roffman, 2013).

Timing Although the infant brain is proportionately closer to adult size than are other body parts, it weighs only about 13 ounces (370 grams), whereas an adult brain weighs a bit more than 3 pounds (1,400 grams). The brain grows faster by weight than any other body part. By the time children are 2 years old, the brain is about 75% of the size and weight of an adult brain. Put another way, it is quite apparent that evolution has provided the brain a “head start,” relative to the rest of the body, in order to direct development.

Though the quantity of neurons remains relatively constant after birth, the number of postna- tal synaptic connections multiplies tremendously. Therefore, the rapid increase in mass is due to the axons and dendrites that grow to form new synapses in response to stimuli. As a new object is seen, a new sound is heard, or a new movement is made, neurons branch and extend their reach to other neurons and form new synapses. By the time a child is 2 years old, some cells may have up to 10,000 connections (Sadava, Hills, Heller, & Berenbaum, 2009). In total, those 100 billion neurons establish trillions of synapses forming a complex yet integrated communication network. When brain development peaks, as many as 250,000 synapses are created every minute.

For every potential stimulus in a person’s environment, there is massive overproduction of synapses during infancy. As new synapses grow, continued stimulation of those connections is key to their survival, maintaining a principle of “use it or lose it.” This physical develop- ment serves as a biological foundation for learning. But as discussed earlier, with regard to sensitive periods and independence of systems, all development does not happen at the same time or at the same rate. The same is true for brain development, as shown in Figure 5.3. Synapses in the visual cortex that are responsible for sight reach peak production between the 4th and 8th postnatal months; synapses in the more sophisticated reasoning centers of the prefrontal cortex do not peak until the 15th month. Notice also that growth in language areas peaks just before infants begin to speak. Therefore, the rate and timing of synapse and dendrite formation are important to understanding development (Tierney & Nelson, 2009; Twardosz, 2012).

Section 5.2Neuropsychology and Brain Development

Figure 5.3: Timing of synapse and dendrite formation ሁ The rate and timing of synapse and dendrite formation vary by age and are important to

understanding development. Notice, for example, that growth in language areas peaks just before infants begin to speak.

Age in yearsAge in months 0 1 2 3-3 -2 -1 4 5 6 7 8 9 10 11 122 3 4 5 6 7 8 9 10 15 1613 1411 12 1

Visual/auditory cortex (seeing and hearing)

Prefrontal cortex (higher cognitive functions)

Angular gyrus/Broca’s area (language areas/speech production)

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Source: From R. A. Thompson and C. A. Nelson, “Developmental science and the media: Early brain development,” American Psychologist, 56(1): 5–15. Copyright © 2001. Reprinted by permission of the American Psychological Association.

The timing of brain development is important to understanding its processes. When peak development for a particular process occurs at a later age, the brain remains plastic (more adaptable) for a longer time. That is, if a part of the brain is damaged before it has begun its major synaptic growth, other cells can take the place of those that are damaged. This ability to adapt due to experience (whether due to damage or ordinary behavior) is called neuroplasticity.

Pruning To facilitate neuroplasticity, the brain goes through a process of overproduction of synapses (as shown in Figure 5.4) before engaging in a process of reduction. Although synaptic devel- opment unfolds by genetic programming (maturation), experience dictates which synapses receive the most stimulation and are likely to remain. Conversely, synapses that are not stimu- lated to a particular threshold will go through a natural reduction process called synaptic pruning. Neurons that are less used—and therefore less necessary—are eliminated. This favoritism allows neurons that receive the most stimulation—and thus are interpreted as the most important—to be given space to grow more elaborate connections.

Section 5.2Neuropsychology and Brain Development

Figure 5.4: Neuron growth and pruning ሁ According to scientists, the brain overproduces synapses during early childhood and then goes

through a pruning process later. Neurons that receive the most stimulation are favored over those that receive less stimulation.

Source: From Reynolds and Fletcher-Janzen, Eds, Handbook of Clinical Child Neuropsychology, Figure 4, p. 25. Copyright © 2009. Reprinted with kind permission from Springer Science+Business Media B.V.

Though paradoxical, in this way development of the nervous system actually profits most effectively from the purging of cells. In a manner that is similar to synapse production, timing of pruning also varies by different brain areas. In some instances, pruning of specific areas of the brain is not complete until adolescence or beyond (Selemon, 2013). This process of overproduction and pruning continues while the mind remains adaptive to unique individual experiences.

Myelination In addition to the growth of synapses, the axons of neurons get coated with myelin (refer back to Figure 5.2), which represents the last stage of sophistication of brain development. Myelination, or the process of coating neurons with myelin, is responsible for speeding up the transmission of impulses. This is an important activity, as faster neural processing is neces- sary to move faster physically and to think in more complex ways. Like other aspects of brain development, myelination occurs in a manner predetermined by maturational processes and follows the same patterns described previously with regard to synaptic growth and pruning (Staudt et al., 1993; Tierney & Nelson, 2009).

The myelination of sensory and motor neurons that is essential to early physical development is mostly complete by 40 months, whereas the neurons that are responsible for higher brain functions like reasoning and complex decision making are not myelinated until early adult- hood. Compared to infants with richer experiences, those raised in more limited environ- ments indicative of low socioeconomic status show overall brain differences in both structure and weight (Lawson, Duda, Avants, Wu, & Farah, 2013). That is, when experiences are limited, it makes sense that brain growth is similarly restricted. Not surprisingly, poor nutrition leads to less myelin development as well as a general reduction in brain size, though early treat- ment can often reverse these negative effects (Atalabi, Lagunju, Tongo, & Akinyinka, 2010; El-Sherif, Babrs, & Ismail, 2012; Hazin, Alves, & Rodrigues Falbo, 2007).

Section 5.3Increased Complexity in Neural Organization

S E C T I O N R E V I E W Diagram the transmission of a signal from one neuron to another.

5.3 Increased Complexity in Neural Organization Although maturation processes dictate the course of peak brain development, neurons con- tinue to migrate and form new synapses when children learn how to throw a ball, experience what it is like to get one’s feelings hurt, and acquire the skill needed to graph a geometric equation. Developing brain processes become more apparent when we see the effects of lat- eralization and sex and gender differences. We explore these processes in this section.

Brain Development in Later Childhood The sophistication of brain growth throughout childhood is evident in the growth patterns illustrated in Figure 5.5. These images show extensive mapping of cortical development among individuals between 5 and 20 years of age. Brain scans were obtained every 2 years, and a dynamic map of development was constructed (Gogtay et al., 2004).

Figure 5.5: Brain development through childhood and adolescence ሁ In an extensive project to map brain development, scientists found that axons (white matter)

continued to replace cell bodies (gray matter) well into adolescence.

Source: Image courtesy of Paul Thompson (USC) and the NIMH.

Section 5.3Increased Complexity in Neural Organization

As you can see from Figure 5.5, well into adolescence axons continue to grow and expand connections, supplanting cell bodies in the process. Basic sensory and motor functions mature first, coinciding with the basic learning outcomes of infancy. Speech and language areas come next; areas in the frontal lobe (one of four major brain divisions) that are related to judgment and the inhibition of impulses are last to develop. Because these centers are not mature until after adolescence, some researchers have speculated that immature fron- tal lobe development is linked to the risky behaviors that are indicative of adolescence. This possibility also raises questions about public pol