Transcript Physical Growth - Kelley Kline Phd

Physical Growth
Neurological, Physiological,
and Motor Development
A. Neurological development:
Neural tube:
Prosencephalon (forebrain)
Mesocephalon (midbrain)
Rhombencephalon (hindbrain)
Neural tube continues developing:

At the end of the bumpy neural tube—
telecephalon followed by the diencephalon.

Both make up the forebrain.
Prenatal Neuronal Development:

Neurons & glial cells proliferate rapidly in
prenatal development.

Fetus has majority of neurons it will have
in life by third trimester (7-8 month).

Neuronal migration—cells migrate to
different CNS locations.
What is a neuron?
Prenatal synaptic development

Synapses (synaptogenesis) are formed at a
rapid rate.

There are trillions of synapses present at
birth. This drops dramatically by
adulthood.
What is a synapse:
Why do we lose cells?

1. Programmed cell death- as new
synapses are formed, surrounding neurons
die to provide space for the new
connections.

2. Synaptic pruning- inactive neurons-removed to free up room for active
neurons.
Brain Development: Infancy
Brain Growth:
 myelination: Areas associated with motor
& mental functions.

cortical & subcortical connections
 lobe activity
 neural plasticity: capacity of brain to
change in response to experience &
chemicals.
Brain development: Toddlerhood

Rapid development 2nd & 3rd yr

Cerebral cortex:
Auditory & Visual cortex
Movement & coordination
Language
Frontal cortex
Brain Development: Childhood

By 6 yrs old brain is 90% of adult weight
Increased connections between all brain
regions
 Communication abilities
 Memory
 Motor
control
 Cognitive abilities
Brain Development: Adulthood

Aging Brain
 weight after 30
How?
-loss of white matter or loss of gray matter
Prefrontal cortex
 connections
Hemispheric Specialization:

Right H.

Left side of body

Music/melodies
 Visual-spatial abilities
Left H.
right side of body
language/speech
logic, analytic
Infants show hemispheric
specialization early.

The majority of newborns process speech
sounds by the left hemisphere as measured
by scalp potentials.
Neural Plasticity: Rosenzweig study

Rats from same litter put into 1 of 2
environments: enriched (E) or impoverished
(I) for 3 months.

“E” environment- large, well-lit, communal
cages- with toys (wheels, ladders, platforms)
changed daily. Rats also explored a maze
once a day.

“I” environment- each rat was placed in a
small, isolated, dimly lit cage .
Rosenzweig (1996): Findings

1. “E” rat brains weighed 4% more than “I” rat
brains.

2. Occipital region of “E” rat brains showed
greatest gain (6%).
3.
Neurotransmitter enzyme levels were greater in
the “E” rats.
4.
Dendritic connections were grater in “E” rat
brains.
B. Motor Development:

Infants--born with little motor development.

Within a year, most infants crawl & walk.
Factors Influencing motor development

1. Maturation.

2. Enriched environment–interesting &
novel stimuli promotes cortical
development.

3. Caregivers—encouragement works.
1. Grasping:

Infants vary -grip on an object based on its
size, shape, texture, & their hand size.

For small objects, infants use thumb &
index finger. They use all fingers of 1 hand
or both hands for larger objects.

Older infants (8 mos.) use visual cues to
guide their grasping, younger infants rely on
touch.
2. Locomotion:

1.First transition -infants show stepping
reflex –ends at 3-4 mos.

2. Second transition- in 2nd half of year,
stepping movements occur again.

3. Third transition – Infants walk
unsupported (12 mos.+)
Theories as to how we learn to walk?

1. Motor cortex develops– frontal lobe takes 1
year to mature for us to walk.

2. Motor programs– we develop motor programs
in spinal cord that guide walking.

3. Cognitive plans—infants have mental
representations for walking.

4. Dynamic Systems view—interaction of
multiple factors (perceptual, neurological,
emotional, etc.)
Factors that promote early walking:

1. Physically handling infants

2. Giving infants practice in motor tasks

Zelazo & coworkers (1972) --mothers of
newborns had infants practice stepping
reflex a few min. a day.

These babies walked--earlier than a control
group given no practice.
C. Physical Growth:

Why do we grow slowly?

We need exposure to social environmental
stimulation to develop the frontal lobes.
Growth patterns in development:

1. Cephalocaudal (from head downward).
2. Proximal-distal (from center outward).
Internal organs develop earlier than the
arms and hands.
Factors that influence height & weight:

1. Genetic factors – accounts for most of
the variance.

2. Gender Girls-taller than boys from 2-9 yrs.
 Girls have growth spurt from 10-14 yrs.
 Boys show growth spurt from 10+
Weight pattern is similar.
3. Hormonal influences-Growth
Hormone (GH)

GH, produced by the pituitary gland
(brain), induces growth in the body.

GH stimulates the liver & skeleton to
release somatomedin, which promotes cell
duplication in the bones.

This promotes growth beyond (4 feet).
Environmental factors (growth):

1. Nutrition – When healthy food is
rationed, growth rates decline.

E.g., During WWII growth rates declined.
In prosperous times, when food is easy to
come by growth rates increase.
2. Does food supplementation improve
growth rates?

Yes!!

Super et al., (1990) showed that giving food
supplements to families for 3-4 yrs,
prevented growth retardation compared
with controls.

Also works with vitamin supplements.
3. Can children with retarded growth
catch up to their peers?

Yes. It depends on severity, duration, &
timing of deprivation (nutrition) & therapy.

Catch-up growth due to severe malnutrition
may be limited to certain aspects of growth.

Children starved early (prenatal+) will show
only modest gains if that.
Are we growing heavier?

Yes. Obesity rates are rapidly rising.

Appears to have risen in children
dramatically within the last decade.

Why?
 Sedentary lifestyle
 High-fat food
Why do kids gain too much?

1. Genetics Adoption studies show biological children of
“heavy” parents reared apart—are more likely to
be heavy themselves (Stunkard et al., 1986).

2. Modeling (what & how do parents eat)

3. SES
Critical periods for obesity:

1. Infancy-

2. Child is 4 yrs-old