Chapter 3
Growth in infancy
Body size
● Newborns lose weight first 3 days and gan an ounce a day for several months
● Birthweight doubles by 4 months and triples by 1 year
● An average 7 pound newborn will be 21 pounds at 12 months
● 24 months most children weigh 28 pounds and have more than a foot in height
● Each numbers is a norm: a standard for a particular population
○ Healthy babies can be larger or smaller due to genetic diversity
Norm: an average, or standard, calculated from many individuals within a specific
group or population
● Each checkup growth is compared to that baby’s previous numbers
Measurements are expressed as percentile: a point on a ranking scale of 0 to 100.
The 50th percentile is midpoint; half of the people in the population being studied
rank higher and half rank lower
● If baby’s percentile changes markedly (up or down), that is a signal that
something might be wrong
○ If 30th-10th percentile, might be a failure to thrive.
○ If weight moves up from 30th to 70th, especially if hight is still close to
30th percentile, overfeeding might be the issue
Sleep
● Newborns sleep about 15 to 17 hours a day, w/ every week bringing few more
waking minutes
● First 2 months the norm for total sleep is 14 1/4 hours, 3 months 13 1/4 hours,
12 months 12 3/4 hours
● Preterm babies may seem to be frequently dozing, never in deep sleep b/c of
constant lights and frequent feedings
● Half the sleep from full-term newborns is REM (rapid eye movement) sleep-
flickering eyelids and rapid brain waves, may indicate dreaming
● Slow-wave sleep, or quiet sleep increases at 3 to 4 months
Bed-sharing: when two or more ppl sleep in the same bed
Co-sleeping: a custom in which parents and their children sleep together in the
same room
Brain Development
Brain basics:
● neuron: one of billions of nerve cells in the central nervous system, esp. in the
brain
, ● cortex: 6 outer layers of the brain in humans and other mammals —thinking,
feeling, and sensing involve the cortex
● prefrontal cortex: the area of cortex at the very front of the brain that
specializes in anticipation, planning, and impulse control (inactive the first
months of infancy becoming more efficient in childhood and adolescence)
● axon: fibre extends from a neutron and transmits electrochemical impulses
from that neuron to the dendrites of other neurons
● !dendrite: a fibre that extends from a neuron and receives electrochemical
impulses transmitted from other neurons via their axons
● synapse: the intersection between the axon of one neuron and the dendrites
of other neutrons
● neurotransmitter: brain chemical that carries information from the axon of a
sending neuron to the dendrites of a receiving neuron
● Limbic system: the parts of the brain that interact to produce emotions,
including the amygdala, the hypothalamus, and the hippocampus. Many other
parts of the brain also are involved w/ emotion
● Amygdala: a tiny brain structure that registers emotions, particularly fear and
anxiety
● Hippocampus: a brain structure that is a central processor of memory,
especially memory for locations
● Cortisol: the primary stress hormone; fluctuations in the body’s cortisol level
affect human emotions
● Hypothalamus: a brain area that responds to the amygdala and the
hippocampus to produce hormones that activate other parts of the brain and
body
Head-sparing: a biological mechanism that protects the brain when malnutrition
disrupts body growth. The brain is the last part of the body to be damaged by
malnutrition
Exuberance and Pruning
Early dendrite growth is called transient exuberance: the great but temporary
increase in the number of dendrites that develop in an infant’s brain during the
first two years of life.
Exuberant b/c is is rapid and transient b/c some is temporary. Expansive growth is
followed by pruning
Pruning: where unused brain connections atrophy and disappear to enable
children to connect the neurons needed in their culture
– Very beneficial b/c babies can discard the excess in order to think more clearly
Every’s experiences sculpt the brain. Some are called:
● Experience-expectant: brain functions that require certain basic common
experiences in order to develop normally
○ Every child needs to develop language
● Experience-dependent: brain functions that depend on particular, variable
Growth in infancy
Body size
● Newborns lose weight first 3 days and gan an ounce a day for several months
● Birthweight doubles by 4 months and triples by 1 year
● An average 7 pound newborn will be 21 pounds at 12 months
● 24 months most children weigh 28 pounds and have more than a foot in height
● Each numbers is a norm: a standard for a particular population
○ Healthy babies can be larger or smaller due to genetic diversity
Norm: an average, or standard, calculated from many individuals within a specific
group or population
● Each checkup growth is compared to that baby’s previous numbers
Measurements are expressed as percentile: a point on a ranking scale of 0 to 100.
The 50th percentile is midpoint; half of the people in the population being studied
rank higher and half rank lower
● If baby’s percentile changes markedly (up or down), that is a signal that
something might be wrong
○ If 30th-10th percentile, might be a failure to thrive.
○ If weight moves up from 30th to 70th, especially if hight is still close to
30th percentile, overfeeding might be the issue
Sleep
● Newborns sleep about 15 to 17 hours a day, w/ every week bringing few more
waking minutes
● First 2 months the norm for total sleep is 14 1/4 hours, 3 months 13 1/4 hours,
12 months 12 3/4 hours
● Preterm babies may seem to be frequently dozing, never in deep sleep b/c of
constant lights and frequent feedings
● Half the sleep from full-term newborns is REM (rapid eye movement) sleep-
flickering eyelids and rapid brain waves, may indicate dreaming
● Slow-wave sleep, or quiet sleep increases at 3 to 4 months
Bed-sharing: when two or more ppl sleep in the same bed
Co-sleeping: a custom in which parents and their children sleep together in the
same room
Brain Development
Brain basics:
● neuron: one of billions of nerve cells in the central nervous system, esp. in the
brain
, ● cortex: 6 outer layers of the brain in humans and other mammals —thinking,
feeling, and sensing involve the cortex
● prefrontal cortex: the area of cortex at the very front of the brain that
specializes in anticipation, planning, and impulse control (inactive the first
months of infancy becoming more efficient in childhood and adolescence)
● axon: fibre extends from a neutron and transmits electrochemical impulses
from that neuron to the dendrites of other neurons
● !dendrite: a fibre that extends from a neuron and receives electrochemical
impulses transmitted from other neurons via their axons
● synapse: the intersection between the axon of one neuron and the dendrites
of other neutrons
● neurotransmitter: brain chemical that carries information from the axon of a
sending neuron to the dendrites of a receiving neuron
● Limbic system: the parts of the brain that interact to produce emotions,
including the amygdala, the hypothalamus, and the hippocampus. Many other
parts of the brain also are involved w/ emotion
● Amygdala: a tiny brain structure that registers emotions, particularly fear and
anxiety
● Hippocampus: a brain structure that is a central processor of memory,
especially memory for locations
● Cortisol: the primary stress hormone; fluctuations in the body’s cortisol level
affect human emotions
● Hypothalamus: a brain area that responds to the amygdala and the
hippocampus to produce hormones that activate other parts of the brain and
body
Head-sparing: a biological mechanism that protects the brain when malnutrition
disrupts body growth. The brain is the last part of the body to be damaged by
malnutrition
Exuberance and Pruning
Early dendrite growth is called transient exuberance: the great but temporary
increase in the number of dendrites that develop in an infant’s brain during the
first two years of life.
Exuberant b/c is is rapid and transient b/c some is temporary. Expansive growth is
followed by pruning
Pruning: where unused brain connections atrophy and disappear to enable
children to connect the neurons needed in their culture
– Very beneficial b/c babies can discard the excess in order to think more clearly
Every’s experiences sculpt the brain. Some are called:
● Experience-expectant: brain functions that require certain basic common
experiences in order to develop normally
○ Every child needs to develop language
● Experience-dependent: brain functions that depend on particular, variable
