Body, Brain, and Health

Chapter 5

The Endocrine System the body’s “slow”

chemical communication system

a set of glands that secrete hormones into the bloodstream

Hormonal Influences on Growth and Development

Neural Communication

The Brain and Nervous System

• Neurons– Dendrite, cell body, and axon

Principles of Growth

• Cephalocaudal principle– Growth occurs in a head-to-tail direction

• Proximodistal principle– Growth and development of muscles from

the center outward to the extremities

• Orthogenetic principle– Development starts globally and

undifferentiated– Moves toward increasing differentiation and

hierarchical integration

The Infant

• Synaptogenesis– Growth of synapses, during childhood

• Synaptic pruning– Removal of unnecessary synapses

• Developing brain has plasticity– Responsive to the individual’s experiences

and can develop in a variety of ways

Figure 5-2

Plasticity

• Responsiveness to experiences– Can be negative

• Vulnerable to damage• Environmental deprivation

– Can be positive• Aids in recovery from from injury• Can compensate for each other• Can benefit from stimulation• Allows for adaptability

Visual-spatial

Emotional Content of Language

Brain Lateralization

Our Divided Brain

large band of neural fibers

connects the two brain hemispheres

Corpus callosum

Brain Development

• Never truly complete– Changes occur across lifespan

• Growth spurts in infancy, childhood and adolescence

• Full adult weight by about age 16

• Processing speed increases in adolescence

• Myelination continues into adulthood

The Changing Brain

• Brain development is never truly complete

• Neurogenesis– Process of generating new neurons

• Elderly adults may end up with 5–30% fewer neurons than early adulthood– Neuron loss greater in areas that control

sensory and motor activities

• Increased activity in the prefrontal cortex

Brain Development The Aging Brain

– Gradual and mild degeneration

Elderly adults– 5-30% fewer neurons than younger adult– Greater loss in sensory-motor areas– Plasticity still possible

Main result of age is slower processing

• Programmed theories of aging

– Maximum life span (species specific)

– Hayflick Limit – cells from embryos divide a limited amount 50 ± 10; for adult cells even less

telomeres

• Random error theories of aging

– Free radicals – toxic by-products of the metabolism of O2 damage cells and their functioning (also damage DNA)

• Interaction of the two – or more