Chapter 3 Physical Development

3.1

Patterns of Growth

Cephalocaudal

CapGrowth starts at the top & moves downward.

Cephalocaudal (ceph alo caudal)Sequence in which the earliest growth always occurs at the top.

Large proportion of total body Occupied by head

Prenatal developmentEarly infancy

Growth starts at head Physical growthDifferentiation of featuresShoulders, etc. downward

Patterns of Growth

Cephalocaudal cont.Sensory & motor development

See objects before control torsoUse hands before walk or crawl

Nevertheless, use feet to touch something (12 weeks) before hands (16 weeks)

Patterns of Growth

Proximodistal

PenisSorry, all I could think of.

ProximodistalGrowth starts at center & moves outward

Proximodistal (proxi mo distal)(Sensory & motor development)

Sequence in which growth starts at center of body & moves toward extremities

Sensory & motor development Control muscles of trunk & arms

before hands

Patterns of Growth

Independence of Systems

Body systems grow & mature independentlyNervous system matures rapidlyBody size slower

Rapid Growth Slow Growth

Brain Development

Cephalocaudal principle indicatesBrain closer to adult size than any other physical structure

Brain Development

The Brain

At Birth 100 billion neurons Areas of brain do not mature uniformly.

Prefrontal cortex finished developing when?

NeuronsAxon Dendrites Myelin sheathTerminal buttonsSynapses

Brain Development

Axon

Carries signals away from cell body

Dendrites Carry signals toward cell body

Brain Development

Brain Development

NeuronInfo processing nerve cellAxons & dendrites

Myelin sheathLayer of fat cellsEncases & insulates most axonsMyelination continues into adolescenceHelps electrical signals travel faster down axon

How Do Infants Grow and Develop Physically?

Neurons

Terminal buttonsRelease neurotransmitters into synapses

SynapsesTiny gaps between neurons' fibers

Synapse

Changes in Brain Regions

1st yr’s of lifeNeurons change in 2 significant ways

1. Myelination2. Increase in neural pathways

How Do Infants Grow and Develop Physically?

24 monthsAt birth 1 month 3 months 15 months

The Development of Dendrite Spreading

Brain Development

Synapses: Tiny gaps between neurons' fibersNeurotransmitters

“Blooming” & “pruning”

How Do Infants Grow and Develop Physically?

Changes in Brain Regions

Blooming (development or increase) in synaptic overproduction

Vary considerably by brain region

Example of blooming in a region:Visual cortex

Blooming peaks @ 4 mo.'s

Changes in Brain Regions

Prefrontal cortex Higher-level thinkingSelf-regulationNot fully developed until @ 23 yrs.

Most prolonged development of any brain region

Peak of synaptic overproduction @ 3 yr ageAdult density achieved in adolescenceHeredity & environment affect timing

Changes in Brain Regions

Changes in Brain Regions

Pruning (decrease) in neurons

Unused connections replaced by other pathways or disappearVary considerably by brain regionBegins @ early adolescence & ends @ age 16.

How Do Infants Grow and Develop Physically?

40

70

60

0

50

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10

Syn

aptic

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sity

10,000100 200 300 400 500 600 1000 1500 2000 3000 4000 6000 8000800

Age in days (from conception)

Synaptic Density in Human Brain from Infancy to Adulthood

Adolescent Brain

http://dsc.discovery.com/tv-shows/discovery-presents/videos/understanding-the-brain-teenagers.htm

Increased Sophistication

Adolescence2nd wave of:

Overproduction of synapsesPruning

Prefrontal cortex changes rapidlyImproved control over:

PlanningAttentionGoal directed activity

Poor risk assessment

Increased Sophistication

AdolescencePreform poorly on tests of emotions

Late adolescence emotional processing moves to frontal lobe

Improvement in risk assessment

The BrainCerebral cortex

Covers forebrain like a wrinkled cap2 hemispheres (halves)Lateralization

Specialization of function in one hemisphere or other

Ex: Language, left hemisphere

Lateralization

Brain organized contralateral (other side)Information for right side transmitted to leftEach hemisphere has specific brain functions

http://www.youtube.com/watch?v=XxSmOOaXrHk

LateralizationHandedness:

Most right handFootedness:

Most right footOcular Dominance:

Right 2/3Left 2/3

Some neither Not related to hand dominance

Facial Asymmetry: Left side of the face is more expressive of emotionRight displays verbal information

Sex & Gender Differences in Brain Development

Girls better at left-brain dominated Language Better at understanding nonverbal cues

Jack did not notice Dr. mad

Boys better at right-brain dominated

Mathematical reasoning

Sex & Gender Differences in Brain Development

Equal, F&MAchievement motivationVisual or auditory learningAnalytic ability

Sex & Gender Differences in Brain Development (Females)

Corpus callosum Connects hemispheresThicker in females

Limbic systemsLarger

Frontal CortexDecision makingDenser

Sex & Gender Differences in Brain Development (Males)

AmygdalaFight or FlightLarger in males

More developed spatial skills

Sex & Gender Differences in Brain Development

Social rolesDependent upon cultureU.S. social bias

Girls expected to be nurturing & empathic Boys?

Sex & Gender Differences in Brain Development Males

More variation in personalityMore variation between males

In skills