Psych 125Human Development

Christopher GadeOffice: 1031-G

Office hours: Tu 12-1:30 and by apt.Email: gadecj@gmail.com

Class: T 1:30-4:20 Room 2210

Development After Birth

• When newborns enter the world, they differ from their adult counterparts in a number of ways.– Small size– Imbalanced dimensions (head size, extremities)– Underdevelopment (brain, muscle, bone)– Different chemistry (hormones, neurotransmitters)– Little ability to interact with their environment

Biology-Based Growth in Life• Each of us grows in slightly different ways, but all

of us follow a fairly similar path. Moreover, we develop biologically in a number of ways.

– Physical development (size, proportion, content)

– Brain and nervous systemdevelopment (size, structure,and function)

Basics at Birth• Most newborns (95% of them born in the US) are

born between 18-22 inches long and 5 ½ to 10 pounds.

• Most exceptions to this are due to external factors– Mother’s diet• video

– Mother’s smoking– Genetic problems– Prenatal problems– Premature births

Tracking Physical Growth• Infancy (0-2 years) – weight rapidly increases (2.5 –

5x), height increases (1.5 – 2x), and muscle mass begins to increase

• Early childhood (2-6) – weight and height increase, but slowly. Differentiation between individuals becomes very noticeable (fat, muscle, height, weight)– Exceptional differences in size are related to experience

• Diet (malnourishment and overeating)• Growth hormone deficiency – the absence of deficiency of a

growth hormone produced in the pituitary gland– Genetic, structural, stress related

• Prenatal experience (smoking, stress, other teratogens)• Physical ailment (sickness, injury)

More on GHD

Tracking Physical Growth• Middle and late childhood (6-11) – “dormancy” in

physical growth (1-2 inches and 5-7 pounds per year). Muscle mass, bone development, coordination, and better proportions mark this stage of physical development.

Tracking Physical Growth• Puberty (9/11 – 15/17) – massive amounts of physical

change occur due to a rush of hormones – chemical substances secreted by the hypothalamus and the pituitary gland.– Reproductive growth (physical and capability growth)– Height and weight growth (men = muscle, women = fat)– Physical changes in voice (men), breast size, hair, skin, and

skeletal system– Women = earlier and slower; estradiol (more overall

increase) and testosterone (2x)– Men = later; testosterone (8x) and extradiol (small increase)– Note: the onset of puberty has been linked to social and

nutritional factors (diet, stress, etc.)

The Social Impact of Early Maturation• Precocious puberty – the very early onset

and rapid progression of puberty– Occurs much more often in girls than boys

(10x)– Early development impact girls negatively at

the time• Riskier behaviors, more emotional and social

problems– And impacts girls negatively in the future

• Poorer school performance, life choices that are similar to older peers, more time with older peers, more emotional problems, more drug and alcohol problems

– These same impacts don’t appear to occur for boys

Tracking Physical Growth• Post-puberty to adulthood to elderly age– We grow until our early to mid twenties– At around thirty our bodies begin to slowly decline

• More fat collects in specific areas• We begin to shrink (men = 1 inch from 25 to 75, women 2 inches from

25 to 75)• We lose fat under our skin (wrinkles)• Our skin loses its elasticity and becomes colored from experience• Our muscle mass (sarcopenia) and elasticity also decline• Out bone strength and density decrease

The Later Years of Change

• From the age of 50 on, the decline of the physical body becomes much more rapid– Females experience menopause

• Biological change – reproductive abilities, bone density, muscle density

• Chemical change – estrogen (causes hot flashes, fatigue, nausea, and other side effects)

– Physical appearance changes more rapidly– Physical ailments become much more common

(cholesterol, circulatory, muscular, skeletal, lung related)

– Note: Many of these changes can be offset to an extent with both cognitive and physical exercise

Now onto another type of change

• Now that we’ve discussed how we progress throughout life physically…

• In this next section, we’ll discuss how we progress in our brain and nervous system.

Brain and Nervous System Development

• At birth, our brains have several important characteristics to them.– Structure – areas of the brain

that are associated with specific functions

– Lateralization – halves of the brain that are associate with specific functions

– Neural plasticity – the ability for the brain to adjust to physical and environmental changes

More on Neural Plasticity• At birth, our brain has nearly as many neurons

(60-100 billion) as we have in adulthood.• The difference is, very few synapses between the

neurons are formed yet.

What causes this growth in connections?• Experience based

formations– Language example (more

activity in specific areas)– Deprivation example (less

activity)

• Problem and growth related rerouting– Early damage example (right

hemisphere took over control of language)

Other Growth-Related Changes in Our Nervous System

• Myelination – the covering of the dendrites of neuron cells with fat cells that speeds up the communication process between neurons– In class example

Growth During Childhood• Synaptic “pruning” – the reduction in synapses that

begins at about 1 year of age• Lobe development– 3-5 frontal lobe growth (planning and organization)– 5-15 parietal and temporal lobe (speech/language,

coordination, and spatial abilities)

Growth During Adolescence• Development of the

amydala and limbic system occur rapidly at this stage– Greater range of emotions– Stronger emotions

• Development of the prefrontal lobe is very slow (doesn’t complete until around 25)– Control of planning and

though– Self-regulation and self-

preservation

The Decline in Adulthood• As we age, our brains slowly

begin to lose weight (5-10%from ages 20 to 90)– Loss of synapses through

continued “pruning”– Loss of myelination– Possible loss of neurons• Basic cell death• Neurogenesis alternative

– Early findings of neurogenesis in the hippocampus and olfactory bulb

– New attempts to prove that with exercise and challenge, neurogenesis can occur throughout the brain

A Note on Brain Development and Experience/Exercise

• Numerous studies have shown that exercise and experience both play a role in the successful function of the brain– Video• Greater synapse

density• Greater blood flow to

cells• Possible increase in

neurogenesis

That’s it for today…• Reviewing:– In this class we addressed how our bodies develop

physically– We also discussed how our brains developed

physically

• Foreshadowing:– In the next class, we look at the development of

health and health related problems