Chapter
5: CHAPTER OUTLINE
I.
Building blocks of growth and
development
Human
grow complex process occurs over many years
Average
Celaic
syndrome-- cannot absorb nutrients from food, stunts growth
Catch-up
growth—body’s struggle to get back to genetically programmed size
Climate
impacts growth (colder-shorter and heavier)
Children’s
height increases most in warm months
A.
Endocrine System-- Body’s Hormonal System Secretes Chemical Hormones Directly
into Blood Stream
1. Endocrine gland-- key gland of hormone system
2. Pituitary gland
a. “master” endocrine gland located at base of
brain
b. directly controlled by hypothalamus
c. triggers release of hormones from all other
glands and produces growth
hormone
d. growth hormones-- directly regulate growth
i.
children lacking growth hormones unlikely to exceed 4’
ii.
adults more effectively treated with
growth hormones
iii. growth hormones in children early and short
puberty
3. Thyroid gland-- growth and development and
impact on nervous system
deficiency
of gland can lead to lower IQ in infants and slower growth
4. Testes-- endocrine glands that produce male
hormones testosterone and other
androgens
a. testosterone-- specific male hormone released
in high quantities during
adolescence
b. androgens-- general term for male hormones
responsible
for growth, development of male sex organs, and
sexual
motivation
5. Ovaries-- estrogen and progesterone
estrogen
and progesterone -- key female hormone released in high
quantities
during adolescence
i. keys
female growth spurt
ii.
responsible for development of adult
sex organs, breasts, and
pubic
hair
6. Adrenal gland-- secretes hormones that
contribute to maturation of bones and
muscles
7. Endocrine glands continue function throughout
life span
B.
The Nervous System
1. The nervous system components-- brain, spinal
cord, and neural tissue
a. central nervous system-- brain and spinal
cord
b. peripheral nervous system-- neural tissue
extended outside central
2. Neuron-- basic cell unit of nervous system
a. dendrites-- branches that receive signals
from other neurons
b. axon-- long segment of neuron in which signal
is transmitted
c. synapse-- gap between neurons
d. neurotransmitter-- brain chemicals released
across synapse
e. myelin-- fatty sheath on axon that insulates
and speeds neural
transmission
f. brain has as many as 100 billion neurons
3. Brain development
a. birth brain weight 25% of adult, age two 75%,
age five 90%
b. deprivation of experience has negative impact
on brain
i. Hubel
and Wiesel visually deprived kittens lost function in
vision
ii.
strabismus can affect child’s brain
development and vision
iii. brain has difficulty handing integration of
images
c. plasticity-- neural responsiveness to
environmental experience
i.
developing brain highly vulnerable to
damage
ii.
greatest in early development (late
prenatal and early infancy)
iii. development is possible throughout life span
d. lateralization-- increasing dominance of one
hemisphere
i. in most people, left hemisphere adept at sequential processing
(language)
ii. in most people right hemisphere adept at
simultaneous processing
(including
spatial skills and visual-motor ability)
iii.
hemispheres connected by corpus collosum
iv. if one hemisphere damaged, other may take
over
v.
lateralization evident at birth and may
have genetic basis
vi.
hemispheric specialization occurs very
early
vii.
brain never completes development
viii.
brain growth spurts occur at times of cognitive advancement in childhood and adolescence
ix adult brain weight achieved around age 16
x.
myelination continues well into
adulthood
xi. children can be clever or gifted, but are
seldom wise
xii.
brain development associated with risky adolescent behavior
4. The aging brain
a. senility (e.g., Alzheimer’s disease) not
normal part of aging
b. gradual and mild degeneration common
c. decreased levels of neurotransmitters
d. loss of brain weight and volume
e. some loss of neurons common
loss
greatest in areas controlling sensory and motor activity
f. increased senile plaque
g. reduced blood flow to brain
h. plasticity continues throughout life span
i. driven
by new experience
ii.
some self-repair possible
i. performance on some tasks may increase in old
age
C. Principles of Growth
1. Cephalocaudal principle-- head to tail
development
head
growth first, then trunk then legs
2. Proximodistal principle-- center outward to
extremities
a. chest and internal organs before arms then
fingers
b. trunk fills out before arms
3. Orthogenetic principle-- global and
undifferentiated to increased differentiation
and hierarchical integration
single
cell to highly specialized cells (e.g., blood)
II. The
infant
A. Rapid Growth
1. Typical newborn 20” and 7 to 7 1/2 pounds
2.
Early size related to prenatal experience
a. ounce a day, and inch a month gain
b. growth is in spurts
3. Soft bones ossify (harden) and become
interconnected
B. Newborn Capabilities
1. Reflexes--
unlearned, involuntary response to stimuli
a. survival reflexes-- clear adaptive value
breathing,
eye-blink, sucking
b. primitive reflexes-- unclear use
i. Babinski
reflex (toe fanning)
ii.
typically disappear in early infancy
iii. useful for diagnosing neurological problems
iv. expression of primitive not related to later
expression
v. primitive
tend to disappear during early months of infancy
vi.
controlled by subcortical part of brain
vii. disappearance of primitive indicator of normal
nervous system
development
2. Behavioral states-- organized, individual
patterns of daily activity
a. predictable sleep-wake cycles within 6-months
after birth
i. newborns
spend half of time in rapid eye movement (REM)
sleep
ii.
by 6-months about 25-30% in sleep in
REM
iii. REM sleep may regulate (reduce) levels of
stimulation
b. states are highly individualized
3. Sensing and learning
a. sensory systems reasonably functional at
birth
b. infants can learn from experience
c. capacity to move voluntarily and
intentionally is limited
learn
slowly
C. Physical Behavior
1. Locomotor development
a. developmental norms-- typical age of mastery
i. depend
on group studied
ii.
hide good deal of variation
b. principles of growth
i. cephalocaudal
principle, lift head before trunk
ii.
proximodistal principle, trunk
activities mastered before leg or
arm
activities
iii.
gross motor skills-- large muscle (e.g.,
kicking)
iv.
fine motor skills-- hand and feet (e.g.,
writing)
v. orthogenetic
principle, early use whole body and later use
specific
body part
c. crawling, walking, manipulating objects
i. creeping
normally begins around 7 months
ii.
hands and knees crawling normally
begins around 10 months
iii.
significant increase in ability to
explore world
d. walking normally begins around 1 year
i. requires
mature nervous system, muscle development, and need
to
be less top-heavy
ii. experience is critical (use of walkers may
inhibit walking by
restricting
visual-motor experience)
2. Manipulating objects
a. innate grasping reflex weakens
b. pincer grasp-- thumb to forefinger develops
c. increased integration and differentiated
movement
3. Emergence of motor skills
a. rhythmic stereotypes-- repetitive movement
common in early infancy
b. dynamic systems approach-- use feedback to
gain control of motor
skills
c. walking requires sensory feedback
young
toddlers can adjust walking in response to changing body
shape
d. walking is not simply genetically programmed
requires
both nature (maturation) and nurture (sensory and motor
experience)
III. The
child
A. Steady Growth
Steady
but slower (ages 2-puberty)-- 2-3 inches and 5-6 pounds per year
cephalocaudal
and proximodistal principles
B. Physical behavior
1. Can react to changing world
2. Refinement of motor skills (initially
awkward)
a. can run in a straight line
b. jump higher, run faster, throw farther
c. some gender differences (boy slightly better)
3. Improvements in eye/hand coordination often
due to practice
4. Faster reaction times
steady
improvement across childhood
IV.
The adolescent
Puberty--
biological change resulting in sexual maturity and capacity to produce children
A. Growth Spurt
1. Adolescent growth spurt
a. triggered by hormones
b. female peak growth for height around age 12,
male peaks age 13.4
c. female peak weight growth around age 12.5,
male peak age 13.9
B. Sexual Maturation
1. Due to adrenal gland activity and release of
gonadal hormones
2. Gonadal hormones primarily responsible for
secondary sex
characteristics and sexual maturation
a. females
i. menarche-- first menstruation
ii.
normally between ages 11 and 14
iii.
rate differs by ethnicity
iv.
lining of uterus shed
v. menstruation
precedes ovulation
vi.
sexual maturation impacted by ethnicity
(e.g., African
American
and Mexican American earlier)
b. males
i. process
begins with enlargement of testes and scrotum around
age
11
ii.
semenarche-- initial ejaculation
iii.
production of sperm typically comes
after semenarche
3. Variations in timing
a. boys and girls similar levels of hormones
during childhood
b. boys have larger quantities of male hormones
(e.g., androgens)
c. girls have larger quantities of female
hormones (e.g., estrogen)
d. secular trend-- earlier maturation in
industrial societies
better
medical care and nutrition
e. anorexia nervosa-- eating disorder involving
severe dieting
f. stress may delay sexual maturation
marital
and stress of war can delay sexual maturation
C. Psychological Implications
1. Concern with body image
a. more prominent in females
b. negative cultural view of menstruation lead
to negative image
c. boys more positive body images
d. males positive and negative reactions to
sexual maturity
e. changes in relationships with parents
i. conflict
due to increasing independence
ii.
cultural beliefs impact parental
relations (e.g., Mexican
American
boys closer to parents)
iii.
relationships tend to become closer
after puberty
2. Early versus late development
a. early maturation more advantageous for boys
than for girls
i. early
maturing boys more socially competent, self-assured
ii.
late maturing boys more anxious, less
athletic
iii.
early maturing girls less popular, in
older peer group
iv.
late maturation for girls not as
disadvantageous as for boys
b. impact of time of maturity tends to fade with
time
i. may be
some risk of long-term problems associated with early
maturing
girls who engage in risky behavior
(e.g., sex)
ii. early maturing males may be more
conforming
c. timing-of-puberty effect mediated by
adolescent’s perceptions
peer
and family reactions can impact perception
D. Physical Behavior
Muscular
strength and physical competence increases
a. boys outperform girls (differences driven by
biological and social
factors)
b. gap between male and female physical skills
narrowing
V.
The adult
A. Physical Changes
1. Appearance and structure
a. most changes after 40
i. wrinkles,
graying and thinning hair, changes in weight (loss in
later
life)
ii.
activity level decreases (impacted by
age, education, personal
factors)
b. osteoporosis-- disease resulting in loss of
bone mass
i. female, small stature, smokers at risk
ii.
calcium and exercise beneficial
c. osteoarthritis-- aging of the joints due to
use resulting in pain and
restricted movement
2. Functioning and health
a. decreases in physical function in all areas
with time
i. loss
most prominent in later life
ii.
large individual differences in
physiological function
b. decrease in reserve capacity-- ability of
organs to respond to demand
lower
maximal heart rate
c. most over 70 have some chronic impairment
3. Psychological implications
a. stereotypes can lead to “ageism”-- prejudice
against elderly
i. many
old individuals do not see themselves as old (Hurd, 1999)
ii.
stereotype of “old” as inactive and
solitary
b. most older individuals retain sense of
well-being and
function independently
B. The Reproductive System
1. Hormones levels fluctuate (especially monthly
in females)
premenstrual
syndrome (PMS) with symptoms of bloating, moodiness,
and
headaches occur in some women
i. some
question validity of PMS, may be impacted by
expectation
as much as hormones
ii.
severe PMS may be due to hormone levels
iii.
genetic and social factors influence
premenstrual and menstrual
distress
2. Female menopause
a. menopause-- ending of menstrual period in
midlife (i.e., no ovulation or
menstruation)
i. due to
drop in hormone levels
ii.
age of menopause somewhat related to
when mom reached
menopause
iii.
physical effects include hot flashes
(sudden sensation of
warmth
and
sweating) and vaginal dryness
iv.
psychological effects vary greatly
and most women do not
experience
significant psychological problems
b. hormone replacement therapy
(estrogen/progestin) used to compensate
for loss of hormones
i. HRT
may increase risk of heart attack, stroke, or cancer
ii.
short-term HRT may be used
3. Male andropause
a. andropause-- male loss of reproductive
capacity (“male menopause”)
i. decreased
levels of testosterone
ii.
less active sperm (but still capable of
having children)
b. erectile dysfunction often the result of medical
conditions
males
changes more gradual and variable
C. Physical Behavior
1. Slowing down
a. nervous system and motor behavior decline
with age
b. difficulty with balance
many
compensate for balance problem by walking slower
c. motor actions performed more slowly
i. may be
the result of brain changes
ii.
biggest impact on fine motor tasks
iii.
fitness may impact speed
iv.
can compensate so performance on
familiar task is not as
negatively
effected
2. Disease, disuse, and abuse
a. effects of aging confounded with effects of
disease, disuse or abuse
b. aging in absence of disease little effect on
physical and psychological
functioning
c. disuse contributes to steep declines in
physical functioning
body
and brain both need use
d. abuse of body (high fat diet, smoking)
contributes to aging