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PSY 118 Ch. 5

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Daniel Gaona

on 24 February 2016

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Transcript of PSY 118 Ch. 5

Most dramatic & extensive transformation occurs before birth
Ch.5 The 1st 2 years
Biosocial Development
However, there are some major changes that occur within the 1st 2 years
Previously...
1st Major change: Body Size
-Weight typically doubles by 4 months
-Weight triples by a year
*average 7lbs newborn will be 21lbs at 12 months
Height increases too
-typical newborn grows 10 in a year
-2 year olds are 1/2 their adult height
*2 years olds are 1/5 their adult weight (4x heavier than they were at birth)
Growth is measured by percentile
Percentile
: a point on a ranking scale of 0 to 100. *50th percentile is the midpoint
Compare height & weight of child against other children of the same age
Ex. Weight at 30th percentile means 30% of babies weigh less & 70% of babies weigh more
If baby's average suddenly grows more slowly it could be the 1st sign of a medical condition (
Failure to thrive
)
If growth is much higher than the norm it could be a sign of obesity
Brain Growth
Body Growth
-Prenatal & Postnatal brain growth (measured by head circumference) affects later cognition
-If infant becomes sick/malnourished nature slow growth of body BUT not the brain
-Known as
Head Sparing
*Brain is last part of the body to be damaged by malnutrition or illness
*From 2 weeks after conception to 2 years after birth the Brain grows more rapidly than any other organ
Brain is 25% of
adult weight by
birth & almost
75% of adult
weight at age 2
Neurons grow rapidly in the last half of fetal life
Brain continues to grow rapidly after birth.
*Brain is protected by the skull
-which has 2
soft spots
called
fontenelles
Allow skull
to squeeze
through vagina
A newborns head is is proportionally the biggest part of the body
Birthing the
infant's head
can take
hours
*only a few
moments
are needed
for rest of the
body
Communication with CNS begin with neurons (nerve cells)
A
newborn's
brain has
billions of
neurons,
about 70%
in the cortex
Most thinking, feeling, & sensing occur in
cortex
Neuron
-Nerve Cell
-Purpose: sending
& receiving
neural messages.
*100 Billion neurons
*100's of trillions of
connections.
Neural
communication
is a 2 step process

1. generation of
electrical signal (Action Potential)
2. Release of
electrical signal
1. Sodium channels open,
sodium rushes in
2. Potassium
channels open,
potassium start
to leave cell
3. Sodium channels close
4. Potassium channels close
-70 milivolts
-65 milivolts
Threshold
40 milivolts
*Occurs within a few miliseconds
Chemical Signal
Synapse: point
of communication
between
2 neurons
Neurotransmitter:
chemical
messenger
Selective Serotonin
Reuptake Inhibitor
Ex. Prozac
Anti-depressant
Neurotransmitters
1.
Acetylcholine (ACh)
: influences movement, memory, learning
2.
Epinephrine (Adrenaline)
: influences arousal/alertness
3.
Norepinephrine
: influences arousal/alterness
4.
Dopamine
: influences movement, planning, reward
5.
Serotonin
: influences mood, appetite, sleep.
6.
Glutamate
: increases brain activity
7.
GABA
: decreases brain activity
8.
Endorphins (Endogenous Morphine)
: morphine produced by body, reduces pain.

Cerebral cortex divided
into 4
lobes
divided by major "folds"
Larger cerebral cortex increases capacity for learning & thinking
Flaten would equal the size of a large pizza
Frontal Lobe
Responsible for
higher mental
processes
e.g. thinking, decision
making, planning,
anticipation.
Orbitofrontal Cortex
:
Social Behavior, moral
behavior, moral
reasoning, impulse
control
Primary Motor Cortex
Located near the rear of the frontal lobe
Output: Voluntary Controls
areas requiring precise control occupy greater space
The Frontal Lobes: Cognition & awareness (VIDEO)
Frontal Lobe
Prefrontal cortex
gradually becomes
more efficient
over the next 2
decades
*Humans have a larger
frontal cortex relative to body size
than other animals
Experiences & Pruning
At birth brain contains at least 100 billion neurons (More than a person needs)
Newborn's brain has far fewer dendrites & synapses
Dendrites growth is major reason brain weight triples from birth to age 2
Number of dendrites increases 5x by age 2
40,000 synapses are formed every second in infant's brain
Extensive brain growth occurs because head cannot grow enough in womb
Transient exuberance
: great but temporary increase in number of dendrites that develop during 1st 2 years of life
Pruning
: the
process by which
unused
connections
waste away
& die
"If you don't use it, you lose it"
No experience=Death
However
Too many condensed neurons/dendrites equals lower intelligence
*Loss of dendrites increase intelligence
Ex. Chimpanzees' have densely packed neurons
Space allow:
1. dendrites to grow, thus
2. more complex thinking & learning
Hypothesized rapid brain growth & not enough pruning leads to Autism
Brain develops normally
for 1st 6 months, but
then synapses do not
develop normally
By age 2 symptoms are
evident
Autism
: impairments in relationships &
communication skills
plus repetitive/ritualistic
behavior
Autism (VIDEO)
*Infant brains do not develop well without essential experiences

Sensory Deprivation Tank
Experience-dependant brain functions
: brain functions depend on particular variable experiences & therefore may or may not develop in a infant.
Ex. type of caregiver
Experience-expectant brain functions
: brain functions require certain basic common experiences in order to develop normally.
Ex. Every baby needs at least one steady caregiver
Every infant requires sensory stimulation
Severe lack of stimulation stunts the brain
Sensation & Perception
Sensation
: the response of a sensory system (eyes, ears, skin, tongue, nose) when it detects a stimulus
Stimulus
: Anything that elicits
a reaction from our
sensory system
Ex. light, sound,
temperature
Perception
: the mental processing of sensory information when the brain
interprets a sensation
Perception allows us
to organize,
recognize, & use info
provided by the senses
We focus on stimuli that is:
1. Unfamiliar
2. Changing
3. High intensity
(e.g. loud sound)

Sensation precedes perception
Perception leads to cognition (thinking)
*Perception requires experience
*every sense functions at
birth
Some sensations are beyond a baby's comprehension
Ex. letters on a
page
Babies are
fascinated
by simple objects
Babies prevent overstimulation by ignoring stimuli
Sleep
Brain maturation= the ability to sleep through the night
Infants normally sleep 15-17 hours
a day (in 1-3 hour segments
Hours of sleep decrease with
maturity
2 months: 14 1/4 hours
3 months: 13 1/4 hours
6-17 months: 12 3/4 hours
Sleep
There are 2 stages of Sleep
1. Non- REM
Sleep (N-REM)
2. REM
Rapid Eye
Movement
REM Sleep
-Occurs 90-120 minutes after falling asleep
-1st REM last 10 minutes. Get
longer as night progresses
-Increased heart rate, BP, breathing, temperature, eye movement
REM Sleep
-Increased mental activity
-Dreaming Occurs
-Body's Muscles are stopped
*Caused by neurotransmitter
GABA (Cortex) &
Glycine (Spine)

Benefits of REM Sleep
-Processing & consolidating: emotions, memories, & stress
-Boosts mood
-Wake up mentally rested
-Babies spend 50% of sleep in REM sleep

*At 6 months myelination occurs
At 7 months REM can be recorded
REM allows fetus to refine neural connections
Fetus can hear sounds/voices outside the womb
Fetus has preferences to food mother eats
At 3-4 months slow wave sleep increases along with time awake/alert
Gross (big) motor skills
: physical abilities involving large body movements, such as walking, jumping, crawling
Fine (small) motor skills
: physical abilities involving small body movements, especially of hands & fingers
Ex. drawing, picking up a coin
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