As we have noted, the normative changes that occur in the brain with age have potentially profound effects, particularly when these changes result in disease. Con­sequently, considerable resources are put into research on the causes and outcomes of such structural brain changes. In the United States, major research support is provided by the National Institutes of Health. For example, the national Institute on Aging provides re­search emphases in neuroscience and neuropsychol­ogy of aging and provides support for research and training to further the understanding of the aging pro­cess in the structure and functioning of the nervous system. These topics include basic neuroscience to un­derstand the underlying brain mechanisms, sleep and biological rhythms, sensory processes, motor func­tioning, the brain processes underlying cognition, and the various types of dementias.

This research is very important as it provides the basis for understanding future trends in health care. For example, by understanding how the changes
that occur normally in the brain sometimes result in disease or other behavioral problems, policymakers have better data with which to predict future health care needs. With the leading edge of the baby-boom generation now eligible for Social Security, such data are key in creating budgets at the state and federal levels so that the health care needs of these people are met. Thus, it is important that the federal gov­ernment continue to fund research on basic brain processes; indeed, the NIH’s budget has increased steadily over the past decade in response in part to the need to understand brain-behavior relations.

A question that is both crucial and as yet unad­dressed in the United States is whether the brain­imaging diagnostic techniques we considered earlier should be available to everyone regardless of cost and whether the individual has health insurance. The rationing of certain medical interventions and diagnostic tools is a very difficult issue, one that will likely be debated for years to come.

Summary

3.1 Why Do We Age? Biological Theories

of Aging

How do rate-of-living theories explain aging?

• Rate-of-living theories are based on the idea that people are born with a limited amount of energy that can be expended at some rate unique to the individual.

• Metabolic processes such as eating fewer calories or reducing stress may be related to living longer.

• The body’s declining ability to adapt to stress with age may also be a partial cause of aging.

What are the major hypotheses in cellular

theories of aging?

• Cellular theories suggest that there may be a limit on how often cells may divide before dying (called the Hayflick limit), which may partially explain aging. The shortening of telomeres may be the major factor.

• A second group of cellular theories relate to a process called cross-linking that results when certain proteins interact randomly and produce molecules that make the body stiffer. Cross-links interfere with metabolism.

• A third type of cellular theory proposes that free radicals, which are highly reactive chemicals produced randomly during normal cell

metabolism, cause cell damage. There is some evidence that ingesting antioxidants may postpone the appearance of some age-related diseases.

How do programmed-cell-death theories propose that we age?

• Theories about programmed cell death are based on genetic hypotheses about aging. Specifically, there appears to be a genetic program that is triggered by physiological processes, the innate ability to self-destruct, and the ability of dying cells to trigger key processes in other cells.

How do the basic developmental forces interact in biological and physiological aging?

• Although biological theories are the foundation of biological forces, the full picture of how and why we age cannot be understood without considering the other three forces (psychological, sociocultural, and life cycle).

3.2 Appearance and Mobility

How do our skin, hair, and voice change with age?

• Normative changes with age in appearance or presentation include wrinkles, gray hair, and thinner and weaker voice.

What happens to our body build with age?

• Normative changes include decrease in height and increase in weight in midlife, followed by weight loss in late life.

What age-related changes occur in our ability to move around?

• The amount of muscle decreases with age, but strength and endurance change only slightly.

• Loss of bone mass is normative; in severe cases, though, the disease osteoporosis may result, in which bones become brittle and honeycombed.

• Osteoarthritis and rheumatoid arthritis are two diseases that impair a person’s ability to get around and function in the environment.

What are the psychological implications of age – related changes in appearance and mobility?

• Cultural stereotypes have an enormous influence on the personal acceptance of age-related changes in appearance.

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• Loss of strength and endurance, and changes in the joints, have important psychological consequences, especially regarding self-esteem.

3.3 Sensory Systems

What age-related changes happen in vision?

• Several age-related changes occur in the structure of the eye, including decreases in the amount of light passing through the eye and in the ability to adjust to changes in illumination, yellowing of the lens, and changes in the ability to adjust and focus (presbyopia). In some cases these changes result in various diseases, such as cataracts and glaucoma.

• Other changes occur in the retina, including degeneration of the macula. Diabetes also causes retinal degeneration.

• The psychological consequences of visual changes include difficulties in getting around. Compensation strategies must take several factors into account; for example, the need for more illumination must be weighed against increased susceptibility to glare.

How does hearing change as people age?

• Age-related declines in the ability to hear high- pitched tones (presbycusis) are normative.

• Exposure to noise speeds up and exacerbates hearing loss.

• Psychologically, hearing losses can reduce the ability to have satisfactory communication with others.

What age-related changes occur in people’s

senses of touch and balance?

• Changes in sensitivity to touch, temperature, and pain are complex and not understood; age-related trends are unclear in most cases.

• Dizziness and vertigo are common in older adults and increase with age, as do falls. Changes in balance may result in greater caution in older adults when walking.

What happens to taste and smell with

increasing age?

• Age-related changes in taste are minimal. Many older adults complain about boring food; however, these complaints appear to be largely unrelated to changes in taste ability.

• The ability to detect odors declines rapidly after age 60 in most people. Changes in smell are

primarily responsible for reported changes in food preference and enjoyment.

3.4 Vital Functions

What age-related changes occur in the

cardiovascular system?

• Some fat deposits in and around the heart and inside arteries are a normal part of aging. Heart muscle gradually is replaced with stiffer connective tissue. The most important change in the circulatory system is the stiffening (hardening) of the walls of the arteries.

• Overall, men have a higher rate of cardiovascular disease than women. Several diseases increase in frequency with age: congestive heart failure, angina pectoris, myocardial infarction, atherosclerosis (severe buildup of fat inside and the calcification of the arterial walls), cerebrovascular disease (cardiovascular disease in the brain), and hypertension (high blood pressure).

What structural and functional changes occur

with age in the respiratory system?

• The amount of air we can take into our lungs and our ability to exchange oxygen and carbon dioxide decrease with age. Declines in the maximum amount of air we can take in also occur.

• Chronic obstructive pulmonary disease (COPD), such as emphysema, increases with age. Emphysema is the most common form of age-related COPD; although most cases are caused by smoking, a few are caused by secondhand smoke, air pollution, or genetic factors. Chronic bronchitis also becomes more prevalent with age.

3.5 The Reproductive System

What reproductive changes occur in women?

• The transition from childbearing years to the cessation of ovulation is called the climacteric; menopause is the point at which the ovaries stop releasing eggs. A variety of physical and psychological symptoms accompany menopause (e. g., hot flashes), including several in the genital organs; however, women in some cultures report different experiences.

• Hormone replacement therapy remains controversial because of conflicting results about its long-term effects.

• No changes occur in the desire to have sex; however, the availability of a suitable partner for women is a major barrier.

What reproductive changes occur in men?

• In men, sperm production declines gradually with age. Changes in the prostate gland occur and should be monitored through yearly examinations.

• Some changes in sexual performance, such as increased time to erection and ejaculation and increased refractory period, are typical.

What are the psychological implications of age-related changes in the reproductive system?

• Healthy adults of any age are capable of engaging in sexual activity, and the desire to do so does not diminish with age. However, societal stereotyping creates barriers to free expression of such feelings.

3.6 The Nervous System

How do we measure changes in the brain?

• Three types of brain imaging are used in research: computed tomography (CT), magnetic resonance imaging (MRI), and positron emission tomography (PET). Each provides important information about brain structures. CT and MRI scans are used most often in routine diagnosis

of brain diseases. PET scans also provide information on brain metabolism.

What major changes occur in neurons? How does the ability of neurons to communicate with each other change with age?

• Neurons are the basic cells in the brain. Some neurons develop neurofibrillary tangles, new fibers produced in the axon that are twisted.

Large numbers of these are associated with Alzheimer’s disease. Some neurons lose dendrites with age, whereas others gain dendrites.

Damaged or dying neurons sometimes become surrounded by protein and form amyloid plaques. Large numbers of plaques are associated with Alzheimer’s disease.

• Several neurotransmitter levels decrease with age, including those of dopamine, acetylcholine, and serotonin. Some diseases, such as Parkinson’s, Alzheimer’s, and Huntington’s, are related to changes in neurotransmitter levels.

What major changes occur in the autonomic

nervous system?

• Regulating body temperature becomes increasingly problematic with age. Older adults have difficulty telling when their core body temperature drops, and their vasoconstrictor response diminishes. When they become very hot, older adults are less likely to drink water.

• Sleep patterns and circadian rhythms change with age. Older adults are more likely to compensate by taking daytime naps, which exacerbates the problem. Effective treatments include exercising, reducing caffeine, avoiding daytime naps, and making the sleep environment as quiet and dark as possible.

What are the psychological implications of

changes in the brain?

• The term senility no longer has medical meaning, nor do all (or even most) older adults become “senile.” However, many people remain concerned about this issue. Brain changes underlie many behavioral changes, including memory.

Review Questions

3.1 Why Do We Age? Biological Theories of Aging

• What biological theories have been proposed to explain aging? What are their similarities and differences?

• Why do some people argue that diets high in antioxidants can prolong life?

• What are some of the sociocultural forces that operate on the biological theories? What are some examples of these forces?

3.2 Appearance and Mobility

• What age-related changes occur in appearance?

• How does body build change with age?

• How do muscle and bone tissue change with age?

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3.3 Sensory Systems

• What age-related changes occur in vision? What are the psychological effects of these changes?

• What age-related changes occur in hearing? What are the psychological effects of these changes?

• What age-related changes occur in somesthesia and balance?

• What age-related changes occur in taste and smell?

3.4 Vital Functions

• What changes occur with age in the cardiovascular system? What gender differences have been noted? Which cardiovascular diseases increase in frequency with age?

• What changes occur with age in the respiratory system? How are respiratory diseases related to age?

3.5 The Reproductive System

• What age-related changes occur in women’s and men’s reproductive ability?

• How does interest in sexual activity change with age? What constraints operate on men and women?

3.6 The Nervous System

• What structural changes occur with age in the neuron? How are these changes related to diseases such as Alzheimer’s?

• What changes occur with age in neurotransmitters?

• What types of brain-imaging techniques are used, and what structures and processes do they measure?

• What changes occur in people’s ability to regulate body temperature?

• How does sleep change with age?

Integrating Concepts in Development

• How do the various biological theories of aging match with the major age-related changes in body systems? Which theories do the best job? Why?

• Given what you now know about normative changes in appearance, what would you say about the stereotypes of aging you identified in the Discovering Development exercise you did in Chapter 1?

• Why do you think the rates of death from cardiovascular disease are so much higher in industrialized countries than elsewhere?

• How might the age-related changes in the respiratory system be linked with societal policies on the environment?

• What changes in memory and intelligence would you expect based on the changes in the nervous system that occur with aging? (Check your answer against the descriptions of these changes in Chapters 6, 7, and 8.)

Key Terms

amyloid plaques A normative change in the brain involving amyloid protein collecting on dying or dead neurons. A large number of amyloid plaques is a defining characteristic of Alzheimer’s disease.

angina pectoris A painful condition caused by temporary constriction of blood flow to the heart. atherosclerosis A process by which fat is deposited on the walls of arteries.

cataracts Opaque spots on the lens of the eye. cerebrovascular accident (CVA) An interruption of the blood flow in the brain.

chronic obstructive pulmonary disease (COPD) A family of age-related lung diseases that block the passage of air and cause abnormalities inside the lungs. climacteric The transition during which a woman’s reproductive capacity ends and ovulation stops. congestive heart failure A condition occurring when cardiac output and the ability of the heart to contract severely decline, making the heart enlarge, increasing pressure to the veins, and making the body swell.

cross-linking Random interaction between proteins that produce molecules that make the body stiffer. emphysema Severe lung disease that greatly reduces the ability to exchange carbon dioxide for oxygen. free radicals Deleterious and short-lived chemicals that cause changes in cells that are thought to result in aging.

glaucoma A condition in the eye caused by abnormal drainage of fluid.

hypertension A disease in which one’s blood pressure is too high.

menopause The cessation of the release of eggs by the ovaries.

myocardial infarction (MI) A heart attack. neurofibrillary tangles A normative age-related change in the brain involving the production of new fibers in the neuron. A large number of neurofibrillary tangles is a defining characteristic of Alzheimer’s disease. neurons The basic cells in the brain. osteoarthritis A form of arthritis marked by gradual onset and progression of pain and swelling, caused primarily by overuse of a joint. osteoporosis A degenerative bone disease more common in women in which bone tissue deteriorates severely to produce honeycomb-like bone tissue. Parkinson’s disease A brain disease caused by an extreme drop in the neurotransmitter dopamine. plasticity The capability of the brain to adapt its functional and structural organization to current requirements.

presbycusis A normative age-related loss of the ability to hear high-pitched tones. presbyopia The normative age-related loss of the ability to focus on nearby objects, usually resulting in the need for glasses.

rheumatoid arthritis A destructive form of arthritis involving more swelling and more joints than osteoarthritis.

telomeres Tips of the chromosomes that shorten with each replication.

Resources

www. cengage. com/psychology/cavanaugh

Visit the companion website, where you will find tutorial quizzes, glossary, flashcards, and more. You can also access the following websites from the companion website.

Lighthouse International is a leading resource worldwide for information on visual impairment and intervention. Their website provides a wide variety of information and resources and summaries of legislative and advocacy activities.

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The American Heart Association provides a wide range of information, including risk assessments, on its website. Information includes preventive measures, diet recommendations, and basic information about cardiovascular and circulatory diseases. In addition, you can access the American Stroke Association site.

The National Institute on Aging (NIA) publishes several informative brochures and reports about many aspects of physical aging, such as menopause, cardiovascular disease, and sensory changes. All the information is based on scientific research.

Readings

Cozolino, L. (2008). The healthy aging brain: Sustaining attachment, achieving wisdom. New York: Norton. A good overview of brain development through late life; easy to moderate reading.

Jaff, N. (2008). Menopause: The complete guide (rev. ed.). New York: Penguin Group. A good overview of the various changes that occur during menopause; easy reading. Kirkwood, T. B. L. (1999). The time of our lives: The science of human aging. New York: Oxford University Press. A very readable account of the biological and physical changes that occur with age; easy reading.

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