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Physical Development In Infancy

Chapter 4

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Patterns of Growth

• Cephalocaudal pattern: Sequence in which the earliest growth always occurs at the top

• Proximodistal pattern: Sequence in which growth starts at the center of the body and moves toward the extremities


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Height and Weight

• The average American newborn is 20 inches long and weighs 7 pounds

• Most of the newborns are 18 to 22 inches long and weigh between 5 and 10 pounds

• Grow about 1 inch per month during the first year

• By 2 years of age– Infants weigh approximately 26 to 32 pounds– Average 32 to 35 inches in height


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The Brain

• Contains approximately 100 billion neurons at birth

• Shaken baby syndrome - Brain swelling and hemorrhaging

• Positron-emission tomography - Scans pose a radiation risk to babies

• Electroencephalogram - Measure of the brain’s electrical activity


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The Brain

• Brain’s development– Mapping the brain• Brain has two halves• Lateralization: Specialization of function in one

hemisphere of the cerebral cortex or the other


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Figure 4.4 - The Brain’s Four Lobes


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Figure 4.5 - The Neuron


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The Brain

– Changes in neurons• Myelination• Connectivity among neurons increases

– Changes in regions of the brain• Blooming and pruning vary by brain region• Peak of synaptic overproduction in the visual cortex

followed by a gradual retraction– Heredity and environment influence the timing and course

• Pace of myelination varies


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Figure 4.6 - The Development of Dendritic Spreading


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Sleep

• Typical new born sleeps approximately 18 hours a day

• Infant sleep-related problem – Night time waking

• Cultural variations influence infant sleeping patterns

• REM sleep - Eyes flutter beneath closed lids


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Sleep

• Shared sleeping• Sudden infant death syndrome (SIDS): Occurs

when an infant stops breathing, usually at night– Suddenly dies without an apparent cause


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SIDS - Findings

• SIDS is less likely to occur in infants who use a pacifier when they go to sleep

• Low birth weight infants are 5 to 10 times more likely to die of SIDS than are their normal-weight counterparts

• Two recent reviews concluded that breast feeding is linked to a lower incidence of SIDS

• Infants whose siblings have died of SIDS are two to four times as likely to die of it


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Figure 4.10 - Developmental Changes in Rem and Non-Rem Sleep


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Nutrition

• Nutritional needs and eating behavior– Should consume approximately 50 calories per day

for each pound they weigh– As motor skills improve, infants change:• From using suck-and-swallow movements • To chew-and-swallow movements with semisolid and

then complex foods

– Need to have a diet that includes:• Fruits and vegetables


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Nutrition

• Breast versus bottle feeding– Breast feeding is better

• Benefits of breast feeding - Outcomes for the child– Gastrointestinal infections– Lower respiratory tract infections


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Nutrition

• Benefits of breast feeding - Outcomes for the mother– Breast cancer– Ovarian cancer– Type 2 diabetes


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• Mother should not breast feed:– When infected with HIV or some other infectious

disease– If she has active tuberculosis– If she is taking any drug


Nutrition

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Reflexes

• Built-in reactions to stimuli– Govern the newborn’s movements – Automatic

• Rooting reflex: Occurs when the infant’s cheek is stroked or the side of the mouth is touched– Turns his or her head in an effort to find

something to suck


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Reflexes

• Sucking reflex: Occurs when newborns automatically suck an object placed in their mouth– Enables newborns to get nourishment before they

have associated a nipple with food– Serves as a self-soothing mechanism


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Reflexes

• Moro reflex: A neonatal startle response that occurs in reaction to a sudden, intense noise or movement– It is believed to be a way of grabbing for support

while falling

• Grasping reflex: Occurs when something touches the infant’s palms– Responds by grasping tightly


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Gross Motor Skills

• Involve large-muscle activities, such as walking• Development of posture– Posture - Dynamic process linked with sensory

information in the skin, joints, and muscles, which tell us where we are in space

• Learning to walk• The first year - Motor development milestones

and variations


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Figure 4.15 - Milestones in Gross Motor Development


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Gross Motor Skills

• Development in the second year– Toddlers become more skilled and mobile– By 13-18 months• Toddlers can pull a toy or climb stairs

– By 18-24 months• Toddlers can walk quickly• Balance on their feet• Walk backward and stand and kick a ball


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Fine Motor Skills

• Involve more finely tuned movements, such as finger dexterity

• Two types of grasps:– Palmer grasp– Pincer grip


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What are Sensation and Perception?

• Sensation: Occurs when information interacts with sensory receptors– Eyes, ears, tongue, nostrils, and skin

• Perception: Interpretation of what is sensed


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Visual Perception

• Visual acuity and human faces• Color vision• Perceptual constancy– Size constancy: Recognition that an object

remains the same• The retinal image of the object changes as you move

toward or away from the object

– Shape constancy: Recognition that an object’s shape remains the same• Its orientation changes


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Visual Perception

Habituation• Decreased responsiveness to a stimulus after repeated presentations of the stimulus

Dishabituation • Recovery of a habituated response after a change in stimulation


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Figure 4.20 - Visual Acuity During the First Months of Life


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Figure 4.22 - Examining Infants’ Depth Perception on the Visual Cliff


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Other Senses

• Hearing– Changes in hearing • Loudness• Pitch• Localization

• Touch and pain• Smell• Taste


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Intermodal Perception

• Involves integrating information from two or more sensory modalities– Vision and hearing
