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Once body structures reach maximum capacity and efficiency in the teens and twenties, biological aging, or senescence begins.
with each duplication a special type of DNA called telomeres are located at the ends of chromosomes and serve as a cap to protect the ends from destruction. eventually so little remains that cells no longer duplicate at all.
this acts as a brake against somatic mutations (such as those involved in cancer) which become more likely as cells duplicate.
programmed effects of specific genes - "genetic programming theory"
- genetic programming theory proposes the existence of "aging genes" that control certain biological changes such as menopause, grey hair, and deterioration of body cells.
- -telomeres, senescent cells
cells with short telomeres. an increase in the senescent cells also contributes to age related disease, loss of function, and early mortality.
"Random events theory" - Cumulative effects of random events
According to this theory dna in body cells is gradually damaged thru spontaneous or externally caused mutations. As these accumulate, cell repair and replacement become less efficient, and abnormal cancerous cells are often produced.
one probable cause of age related dna and cellular abnormalities is the release of free radicals. Free radicals are naturally occuring, highly reactive chemicals that form in the presence of oxygen. When oxygen molecules break down within the cell, the reaction strips away an electron, creating a free radical. As it seeks a replacement from its surroundings, it destroys nearby cellular material including dna, proteins, and fats that are essential for cell functioning.
Thoughts on Free radicals
- free radicals are thought to be involved in more than 60 disorders of aging, including cardiovascular disease, neurological disorders, cancer, cataracts, and arthritis.
- -although our body produce substances that neutralize free radicals, some harm occurs and accumulates over time.
- -animal species with longer life expectancies display slower rates of free radical damage to dna
Foods that stall free radicals
foods with vitamin C, E and beta carotene.
Aging at the level of tissues and organs - "Cross linkage theory of aging"
- -suggests that over time, protein fibers form links and become less elastic, producing negative changes in many organs.
- -declines in the endocrine and immune systems may also contribute to aging.
What consequences might the DNA and cellular deterioration have for the structure and functioning of organs and tissues?
The cross linkage theory of aging.
Physical changes in the cardiovascular system
- -the timing of change is gradual.
- -only during stressful exercise does heart performance decline with age. under typical conditions it does get worse with age.
- -as the heart muscle becomes more rigid, maximum heart rate decreases, reducing the hearts ability to meet the body's oxygen requirements when stressed by exercise. when artery walls stiffen plaque builds and blow flow to cells is reduced.
- -atherosclerosis-plaque on the artery walls, cardiovascular disease.
- -heart disease has decreased considerably since the mid 20th century, especially in last 20 years due to a decline in cigarette smoke and improved diet and exercise.
- -blacks are more likely than whites
physical changes in the respiratory system
- -like the heart, the lungs show few age related changes in functioning at rest, but during phsyical exertion, respiratory volume decreases and breathing rates increase with age.
- -gradual timing of change
- -vital capacity declines by 10% per decade after age 25. because tissue in lungs stiffens with age making it more difficult for lungs to expand to full volume.
physical change in motor performance
- -athletic skills requiring speed, strength, and gross motor cordination peak in the early 20's.
- -skills that require endurance, arm hand steadiness, and aiming peak in the late 20's and early 30's.
- -less active lifestyles rather than biological aging account for most of the age related decline in athletic skill and motor performance.
physical change in immune system
- -the immune response declines after age 20.
- -this is due to shrinking of the thymus gland and increased difficulty coping with physical and psychological stress.
physical change in reproductive capacity
- -women's reproductive capacity declines with age due to reduce quality and quantity of ova.
- -men show gradual decrease in semen volume and sperm quality after age 35.
Basal metabolic rate (BMR)
- -bmr is the amount of energy the body uses at complete rest.
- -adding some weight btwn 25 and 50 is a normal part of aging because bmr gradually declines.
2 most commonly abused substances
- -cigarette smoking and alcohol consumption
- -smokers who started b4 age 21 are more at risk for many health problems including eye and skin abnormalities, decline in bone mass, heart attacks, stroke, and cancers.
heavy drinkers and alcoholics
- -about 1/3 of heavy drinkers suffer from alcoholism.
- -both hereditary and environmental factors contribute.
- -liver and cardio disease, cancers.
- -crime like drinking and driving fatalities, sexual coercion
- -one quarter of americans are likely to contract an std during their lifetime.
- -women more than men.
- -although aids remains concentrated among gay men and druggies, the incidence is declining in gays.
- -aids is spreading rapidly thru heterosexual contact in poverty stricken minority groups with women at high risk.
- -most rape victims are under 30 and been harmed by men they know well.
- -men who rape usually hold traditional gender roles, approve of violence against women, have difficulty interpreting women's social behavior accurately.
- -cultural acceptance of strong gender typing and of violence contributes to sexual coercion.
- -female inniated sex coercion occurs but is less reported
Premenstrual syndrome (PMS)
- -nearly 40% experience pms usually in mild form
- -some pms is so severe interferes w/ daily life.
psychological stress affecting health?
-chronic psych stress induces physical responses that contribute to heart disease, cancers, and gi problems