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Flashcards in Aging and Death Deck (29):

Definition of Aging and Senescence

-also the 3 aspects of aging

-Aging: all the changes occurring in the body with the passage of time
e.g. growth, development
-they are progressive changes from birth to infancy
-Senescence: the degeneration that occurs in the organ systems after the age of peak functional efficiency
-gradual loss of capacities, to repair and increased susceptibility to disease

*are physical, psychological and social aspects of aging


Rate of aging

-Occurs at different rates among individuals and within individuals -> generally does not cause symptoms


Characteristics of Mammalian Aging (4)

-What influences aging (4)

-cellular and physiological deterioration
-increased mortality with age following maturation
-increased vulnerability to disease
-decreased ability to adapt to stress
-i.e. impaired homeostasis

Influenced by;


"Successful" aging (4)

-Freedom from disease
-freedom from disability
-intact mental capacity
-active engagement with life

*these are very subjective*


-chronological age

-Social roles and age

-Functional age

-Subjective age

-Chronological age is a common marker of old age
-Social roles and age usually guide the expectations or guidelines for people who occupy given positions (i.e. grandmother typically thought of as an old woman)
-Functional age: what you can do and how you look
-Subjective age: those who compensate for limitations of functional age maintain a subjective age
-"you're only as young/old as you feel"



-what medical research is focusing on

-how senescence typically works

-what can lessen the effects

-Australia is an aging nation
-Most medical attention = prevention and treatment of the diseases of age
-Senescence of one organ typically leads to senescence of another organ system (flow on effect)
*organ systems do not degenerate at the same rate

-Personal health and fitness practices can lessen the effects of senescence


Senescence of the skin

-Features of aging skin


-thickness of skin

*Skin = first protective layer - gets exposed to elements, chemicals, damaging radiation etc.
-usually occurs around 40s
-Features of aging skin;
-gray, thinning dry hair
-paper thin, loose skin that sags (due to loss of elastin)
-dry skin that bruises easily and heals slowly
-rosacea - patchy networks of tiny, dilated vessels visible on nose and cheeks
-hypothermia in cold weather and heat stroke in hot weather
-atrophy of cutaneous vessels, sweat glands and subcutaneous fat
-decreasaed vitamin D production causing calcium deficiency
-Photoaging = degeneration in proportion to UV exposure -> skin spots, skin cancer, wrinkling

-Skin becomes thin due to slower turnover of cells


Body Composition over time

-fat, cell mass and bone

-More fat in certain places
-decreased cell mass; lose supporting cells
-Bone mass also decreases



-height: lose 1 cm every 10 years after the age of 40
-less bone mass and a decrease of cartilage turnover

-also, invertebral discs become drier and lose fluid (therefore shortening)


Skeletal system -> aging


-differences between men and women

-Osteopenia: loss of bone mass
-Osteoporosis: loss is severe enough to compromise a person's physical activity and health (unable to maintain bone)
-after 30, osteoblasts less active than osteocytes
-after 40, women lose 8% bone mass per decade, men lose 3%
-estrogen has a protective feature for bone loss - why women lose more


Skeletal system -> aging

-joint diseases
-synovial fluid
-sternocostal joints
-intervertebral discs

*many types of joint diseases
-synovial fluid less abundant and articular cartilage thinner or absent - produces friction that causes pain
-breathing difficult due to calcification of sternocostal joints
-degeneration of intervertebral discs = back pain and stiffness
-herniated discs less common


Osteoarthiritis -> where it is most likely to occur (2)

-occurs in weigh bearing joints and areas of repeated strain


4 types of joint diseases

-neuromechanical (e.g. osteoarthritis)
-Inflammatory (e.g. septic arthritis)
-Immune (rhueumatoid arthritis)
-Metabolic (gout)


Muscular System -> aging

*30% loss of muscle between 30-80
-muscular atrophy causes replacement of lean body mass (muscle) with fat
-muscle strength peaks at 20
-fast-twitch fibres exhibit earliest and most severe atrophy
-Loss of strength


Nervous system and aging

-features of cerebral and neuronal atrophy

-what features suffer most (3)

-effect on autonomous nervous system (what this means)

-Cerebral and neuronal atrophy
-peak development around age 30
-from age 35, 100 000 brain cells die every day
-brain weighs 56% less by age 75
-Cortex thins, gyri narrow, sulci widen
-fewer synapses and neuroglia
-less neurotransmitter and receptors
-degeneration of myelin = slower signal
-motor co-ordination, intellectual function and short term memory suffer most
-autonomic nervous system is less efficient at regulating body temp and blood pressure


Age on Sense organs: Vision

-night vision impaired -> fewer receptors, pupil dilators atrophy and enzymatic reactions become slower
-loss of flexibility of lens
-cataracts or cloudiness of lenses
-glaucoma risks increase (fluid in anterior of eye that causes pressure to build up)


Age on Sense organs; Hearing

-tymphanic membrane and ossicle joints stiffen (can't vibrate as much)
-hair cells & auditory nerve fibres die
-death of receptor cells result in dizziness
-taste and smell is blunted as receptors decline


Endocrine system

-how it degenerates over time

-Pituitary gland

-type 2 diabetes - why more common

-Degenerates less than any other system
-only reproductive, growth and thyroid hormones decline steadily after adolescence
-other hormones secreted at fairly stable rate
-pituitary gland less sensitive to negative feedback inhibition by adrenal glucocorticoids
-response to stress is prolonged
-type 2 diabetes is more common (more body fat decreases insulin sensitivity of other cells)


Circulatory System

-3 things that may occur

-Fat can build up between layers of blood vessels (tunica media, intima and adventitia) and can block blood flow
-varicose veins due to weaker valves
-anemia may result from nutrition, lack of exercise, changes in erythropoiesis, lack of intrinsic factor which reduces vitamin B12 absorption increasing risk of pernicious anemia


Immune system and aging

-Amounts of lymphatic tissues and red bone marrow decline
-fewer hemopoietic stem cells, disease-fighting leukocytes and antigen-presenting cells
-lymphocytes fail to mature
-both types of immune responses are less efficient


Respiratory system and aging

-Declining pulmonary ventilation
-less flexible coastal cartilages
-lungs have less elastic tissue and fewer alveoli
-elderly less able to clear lungs of irritants and pathogens
-therefore more susceptible to respiratory infection and pneumonia
-chronic obstructive pulmonary diseases
-emphysema (damage w/in airsacs) and chronic bronchitis more common


Urinary System and aging

-Renal atrophy - 20-40% smaller by age 90
-loss of nephrons and atherosclerotic glomeruli
-filtration rate decreases leaving little reserve capacity (can't clear drugs as rapidly)
-fluid balance less responsive to hormone and sense of thirst sharply reduced
-voiding and bladder control


Digestive system and nutrition

-dental health affected by reduced saliva
-gastric mucosa atrophies and secretes less acid and intrinsic factor
-intestinal motility decreased due to weaker muscle tone, less fibre, water and exercise
-reduced food intake due to loss of appetite and mobility risks malnutrition
-also due to loss of taste buds


Reproductive system and aging

-males vs. females

-Males; gradual decline in testosterone secretion, sperm count and libido
-fertile into old age but impotence may occur
-Females; more abrupt, rapid changes due to menopause
-ovarian follicles used up, gametogenesis ceases and ovaries cease production of sex steroids
-also an elevated risk of osteoporosis and atherosclerosis


Exercise and Senescence

-Good nutrition and exercise are best ways to slow aging
-exercise provides endurance, strength and joint mobility
-also reduces incidence/severity or hypertension, osteoporosis, obesity and diabetes mellitus
-resistance exercise also reduces bone fractures
-endurance reduces body fat and increases cardiac output and oxygen uptake


Mechanisms of Senescence (theories)
-Replicative senescence
-Cross-link theory
-protein abnormalities
-free radical theory
-autoimmune theory

-Replicative senesecence: decline in mitotic potential with age -> human less have finite no. of cell divisions
-Cross-link theory: 1/4 of body = collagen; over time collage molecules become cross-linked making fibres less soluble and stiff
-Protein abnormalities: Increasingly abnormal structure in older tissues and cells accumulate over time
-Free radical theory: free radicals have destructive effect on macromolecules
-molecules damaged by free radicals are long-lived and accumulate within cell
-Autoimmune theory: altered macromolecules recognized as foreign
-lymphocytes stimulated to attack own tissue


Evolution and senescence

-thought that death occurred for good of species -> leaves resources available for young and healthy
-natural selection wouldn't occur on genes that only affect elderly -> is why aging genes remain with us today


Australian Life

-average lifespan

-oldest age ever achieved

-Average lifespan for;
-Australian boy = 79.9 yrs
-Australian girl = 84.3 yrs
*maximum age reached by human = 122 yrs


Biological death

-2 ways it can be classified

-Clinical death: when someone stops breathing
-Biological death: brain cells die due to lack of oxygen
*no definable instant of death
-some organs function for an hour after heart stops
-usually occurs as failure of particular organ followed by a cascade of other organ failures