Lifespan development-chapter 4

Couvade and the parent-infant bond are similar because both:

are empathetic states

Prenatally, the human head develops from "head to tail" or in a(n) _____ pattern.

cephalocaudal

The onrush of _____ in the male fetus is one reason why neurological sex differences occur in the third month of pregnancy.

testosterone

A reflex occurs without _____ thought.

voluntary

Teratology is the study of:

birth defects

_____ in the uterus has to occur for a woman to confirm her suspicions that she is pregnant.

implantation

Newborn Tabitha enthusiastically moves her arms and legs when her mother pulls a T-shirt over her head and momentarily covers her face. This movement demonstrates one of the reflexes that maintains _____.

oxygen supply

Rebecca had a cesarean section and was taken to the recovery room before she had a chance to cuddle with her newborn daughter. She worries that this lack of connection may impede the _____.

parent-infant bond

After conception, the multiplying cells form into two masses; the outer cells becoming the _____ and the inner cells becoming the embryo.

placenta

Cheryl gave birth one month ago and never wants to begin the day. She lets her baby cry in his crib for long periods of time and finds herself fantasizing about ending his life. Cheryl may be experiencing _____.

postpartum psychosis

A doctor is examining an ultrasound of an embryo and observes a thin line called the _____ running down the middle of the embryo; this will later become the neural tube.

primitive streak

Prenatally, the human head develops in a cephalocaudal pattern, while the extremities develop in a(n) _____ pattern.

proximodistal

Sound waves are to ultrasounds, as _____ is to X-rays.

radiation

Assessing the future occurrence, size, and location of earthquakes in California to reduce harm to cities and towns is an example of _____.

risk analysis

In 1940, no one analyzed the risks of prenatal development; it was assumed that the placenta screened out all harmful substances. Then, there was an increase in the number of babies born blind on an Australian military base that was linked to a(n) _____ epidemic seven months earlier.

rubella

5. All of the following are difficulties likely to affect infants born with fetal alcohol syndrome EXCEPT: A. limb malformations. B. problems with attention and memory. C. problems with language development. D. poor social skills.

Answer: A Infants born with this condition can face lifelong difficulties with attention, memory, learning, thinking, language, and social skills.

_____ is an example of a reflex that maintains oxygen supply, while _____ is an example of a reflex that maintains body temperature.

Hiccupping; tucking in legs

After conception, the multiplying cells form into two masses; the outer cells becoming the placenta and the inner cells becoming the _____.

embryo

1. The development period when the brain experiences the most growth and maturity is the:

fetal period.

An Apgar score of 6 could be explained by a slow _____ and slow breathing immediately after birth.

heart rate

Marta's newborn daughter had problems breathing, was pale, and had limp muscle tone immediately after birth. When a neonatal physician came to the delivery room, she knew Marta's daughter's Apgar score would be less than 4, indicating that _____ is needed.

help

When an infant assumes the fetal position, with the legs tucked close to the body, it is possible that he or she is _____.

cold

Professor Brown is speaking to her class about prenatal development and refers to the brain's advanced outer layers that become more complex and form several folds. Professor Brown is speaking about which part of the brain?

cortex

Jane is 4 months pregnant with her first child. Her husband, Carl, has been complaining of nausea and heartburn and has gained 5 pounds since learning of his wife's pregnancy. Carl may be experiencing:

couvade

Tim has gained 8 pounds and has had frequent bouts of heartburn as his wife's pregnancy has progressed. Tim may be experiencing _____.

couvade

To test the implications of early emotional bonding, scientists have explored infant emotionality by separating monkey babies from their natural mothers in the first days of life, allowing them to be raised by another of their species. This strategy is called:

cross-fostering

The average length of active labor in a first birth is about _____ hours.

12

In the fetal period, the fetus grows from the length of a final thumb joint to about _____ inches in length at birth.

20

A baby is considered preterm if he or she is born _____ or fewer weeks after conception.

35

All teratogens increase the risk of _____ but they do not always cause damage.

birth defects

The development of new connections between neurons is called:

synaptogenesis

Mike and Ted are newborns. Mike's mother finds his sucking reflex is strong, while Ted's mother worries that his sucking reflex is weak. This difference signals that:

the boys are unique individuals.

Newborns affect their families both directly and indirectly. An indirect impact would be that the baby will make the people who created him or her into a mother and father. Which is NOT an example of a direct impact that the child will have on his or her family?

A. a decrease in emotional attachment between the father and mother. B. the impact of the child on the parent's emotionality C. the fetal hormones alter the mother's body chemistry D. an increase in parental brain activity Answer: A

The brain is at the center of our thoughts, emotions, and behavior. More than that, it embodies all that is the self: the memories, dreams, and characteristic ways of thinking that make each person unique. The brain is an organ of astonishing complexity in its function and structure. Researchers estimate that a baby's brain contains about 100 billion neurons, with over 100 trillion (100,000,000,000,000) synaptic connections. But like all other organs, the brain starts out as a much simpler collection of cells in the first days of development after conception. Prenatal development begins with conception, and it is divided into three periods: germinal (0-2 weeks), embryonic (3-8 weeks), and fetal (9-38 weeks). Whereas the embryonic period is the time when most body and brain structures emerge, the fetal period is the time when organs enlarge and mature. The brain is no exception. The most dramatic changes involve the cerebral cortex, which enlarges and rapidly covers the midbrain by 6 months after conception. At this point, the cortex is a relatively thin and smooth sheet of densely packed neurons. Play the animation and watch the rapid growth of the cerebral cortex during prenatal brain development.

At 9 weeks, the beginning of the fetal period, the main structures of the brain are already in place, but the amount of tissue is rapidly increasing because of the birth of new cells and connections. Young brain cells migrate in waves from the innermost layers of the brain to outer locations. In this way, the brain grows, adding layers like the skin of an onion. Having reached their destinations, the neurons now sprout extensions with which they will communicate with other neurons. Each neuron develops extensions of two types—dendrites, which are multiple, short, thin, antenna-like extensions for receiving in-coming signals; and an axon, a single, larger extension that conveys out-going signals to other neurons. The connections between neurons are called synapses—tiny gaps where chemical signals from one cell's axon travel to another cell's dendrite or body. Play the animation and watch the growth of neural networks.

You should know that the brain is highly vulnerable to damage during this time of rapid cell production and synaptic remodeling. For example, when the mother drinks alcohol, the alcohol that passes from the mother to the fetus can cause severe disruptions of brain development, a condition known as fetal alcohol syndrome (FAS). Alcohol interferes with the normal migration of cells and the development of neural networks, yielding an underdeveloped and malformed brain. Infants born with this condition can face lifelong difficulties with attention, memory, learning, thinking, language, and social skills. Other factors can interfere with brain development in the prenatal and infancy periods, including diseases (e.g., rubella, toxoplasmosis, syphilis), medications (e.g., phenobarbital, methadone), pollutants (e.g., lead, mercury), radiation, and malnutrition.

By the 28th week after conception, the birth of new brain cells is largely complete, but the cerebral cortex continues to expand throughout the fetal period due mostly to the proliferation of dendrites, axons, and the support cells of the brain (e.g., glial cells). There is a major structural change occurring at this time. The cortex, a sheet of cells only 2 mm thick, expands greatly in surface area, and becomes wrinkled and folded inside the skull. These "hills and valleys" (gyri and sulci) start to form around week 28 and become more prominent over time. What is the function of these cerebral folds and wrinkles? They permit more points of contact among neurons (synapses) and hence, contribute to the ability of each neuron to connect to and influence hundreds or even thousands of neighboring cells. These vast neural networks allow the brain to become a highly flexible, yet precise control center and processor of information. Play the animation and watch the expansion of the cerebral cortex.

An overabundance of synapses is created in the prenatal period and in the first year after birth, creating a brain with great flexibility for learning. But in order to make a brain that works rapidly and efficiently, many of these early synapses will need to be removed or "pruned." One purpose of pruning is to "customize" an individual's nervous system in response to that individual's unique life experiences. Synaptic pruning—also called synaptic remodeling—begins in the prenatal period and occurs at high rates in infancy and early childhood. Play the animation and watch the customization of neural networks through synaptic pruning.

During the fetal period and extending into early childhood, neural networks grow at a rapid rate; in particular, the extensions of neurons and the gaps between neurons (synapses). Pruning removes some of these gaps, allowing customization to the individual's nervous system and life experiences.

During active sleep, also known as rapid eye movement (REM) sleep, the infant shows a good deal of movement of the face and eyes under closed lids and some body movements, such as tossing and turning. Active sleep occurs at the start of a period of sleep for newborns. This differs from the normal adult pattern in which the adult sleeper first enters a deep-sleep stage and then proceeds to REM sleep. Newborns spend about 8 hours a day, which is 50 percent of their total sleeping time, in REM sleep. The proportion of REM sleep declines rapidly in the months after birth. After age 3 or 4, children spend only about 20 percent of their total sleeping time in REM sleep. Why do newborns spend so much time in REM sleep? Current research suggests that this is nature's way of making up for the newborn's lack of external visual stimulation during sleep. To develop properly, the neural circuits for vision need stimulation, and REM sleep creates patterns of brain stimulation that facilitate this development.

In deep sleep, also known as non-rapid eye movement (NREM) sleep, the newborn is at full rest. Muscle tone and activity are low, and the eyes are still and closed. Breathing is slow and regular. After two or three months, the sequence of active sleep and deep sleep will reverse, and deep sleep will come before active sleep as it does in adults.

In the quiet awake state, the newborn's eyes are wide open, and the infant shows only slight activity. You can expect a mild response to sights, sounds, and touch. Quiet awake may occur shortly after waking, or it may follow a more active period.

In the active awake state, the newborn shows a higher level of activity moving more frequently and occasionally making sounds. The infant's reactions to sights and sounds are stronger than they are in the quiet awake state.

In the earliest days, a newborn's cry is an involuntary reflex just as breathing and eye blinks are reflexes. Crying is controlled by structures in the lower, primitive parts of the brain in response to whenever the infant is in distress and needs comfort or food. After a few months, however, crying becomes more voluntary. At that point, the infant can use her cry to get the caregiver's attention.

In the drowsiness state, newborns and infants open and close their eyes, which usually have a glazed-over appearance. Sleep is not far off!

The top segment of this diagram shows the typical portion of a 24-hour period that a newborn in the United States spends in each of the six states of arousal. Some of you may wonder why new parents often complain of sleep deprivation when newborns are sleeping for 16 hours a day. The challenge for new parents is that newborns get their sleep in short naps that may last for a few minutes to a few hours. Therefore, they can be asleep or awake at any time of day or night. As the chart shows, these round-the-clock bouts of sleep consolidate into a long period of sleep at night and a few naps during the day. Over time, newborns' cycles of arousal across the day gradually shift into the typical adult patterns of sleeping and waking.

In the next several pages, you will have a chance to try your hand at identifying some of the states of arousal in video clips of newborns. When you feel confident that you can identify the state of arousal, select the newborn state below that most closely corresponds to the infant's state that you see in the video clip.

What newborns notice, learn, and do depends on their state of arousal, or their general level of alertness and activity. Developmentalists have identified six primary states of arousal: deep sleep, active sleep, drowsiness, quiet awake, active awake, and crying. As you will see in the screens that follow, each of these six states is associated with its own pattern of activity, such as gross muscle movements, eye movements, breathing patterns, and brain states.

Over a 24-hour period, a typical newborn in the United States will experience about seven sleep intervals and seven waking intervals. The peaks in this diagram represent relatively alert intervals, and the valleys represent periods of sleep. The various states of arousal occur throughout the day and night as the newborn moves between waking and sleeping.

The speed at which impulses travel along neurons increases due to the process known as myelination. This is the development of a form of insulation. Impulses are faster because they can jump from one gap in the insulation to the next. The myelin sheath forms when special cells (oligodendroglial cells) wrap themselves around the axon of a neuron. At 16 weeks after conception, myelination begins in the lower spinal cord of the fetus and progresses to the upper spinal cord, brain stem, cerebellum and posterior part of the internal capsule. All of these structures show myelination at the time of birth.

With the development of the myelin sheath, the axons become insulated, which enables neural impulses to travel faster among neurons because the impulse can now jump from one gap in the insulation of a neuron to the next. We have seen the development of the human brain from two points of view in this activity. The brain grows as waves of new cells migrate from the inside to distant locations. Once in place, they form dense interconnections (neural networks), which, over time, are pruned (remodeled) to create a more efficient information processor. Myelination of the neural fibers improves communication speed between various parts of the brain. This symphony of growth, movement, interconnection, and remodeling creates a brain of stunning complexity—a biological structure ready for learning and interacting in the human environment. Play the animation and watch brain development from early in the embryonic period to a formed fetus.

Sam was born preterm at 22 weeks. He may survive with medical intervention because he has reached the _____.

age of viability

Dr. Nelson is researching the formation of the _____, which is formed from a shell that will become the placenta, and a nucleus that will become the embryo.

blastocyst

Dr. Osbourne is studying the cell mass that is formed about one week after conception; it is also referred to as the _____.

blastocyst

Low-birthweight babies have been found to gain weight more quickly when their caregivers practice a skin-to-skin technique known as _____.

kangaroo care

A study conducted in Milwaukee suggested that a father's _____ acceptance of the birth correlated with easier labor in general.

legal

Anika watches her newborn son, dressed in only his diaper, on the changing table as she grabs a new sleeper. She notices that he tucks his legs up close to his body before he begins to cry. These reflexes are part of the set of reflexes that manages:

maintaining body temperature.

4. The speed of neural impulses along an axon is increased greatly by:

myelination. Myelination is the development of a form of insulation. Impulses are speeded because they can jump from one gap in the insulation to the next.

2. The connections between neurons—where chemical signals from one cell's axon travel to another cell's dendrite or body—are at the synapses.

true The connections between neurons are called synapses—tiny gaps where chemical signals from one cell's axon travel to another cell's dendrite or body.

3. The brain part that expands throughout the fetal period is the cerebral cortex.

true The cortex, a sheet of cells only 2 mm thick, expands greatly in surface area and becomes wrinkled and folded with gyri and sulci inside the skull.