Biology of aging Flashcards
What are the theories of aging?
- Random DNA errors
- specfic gene
- Mutations of cells with age
- Limited # of cell divisions possible
- decreas in cholingergic cells
- Damage from free radicals
- Hormonal alterations
What are the gross changes in the neuroanatomy? what are the implications?
Changes:
- By age 80, 15% weight loss of brain (mostly myelinated structures)
- Increase CNS fluid spaces
- Decrease gyri in bulk, increase sulci widening
Implications:
- Less functioning tissue
- Decrease ability in CNS in all areas
What are the histological changes?
- Decrease # of neurons in cortex, 37% decline in spinal cord axons
- decrease # and and size of dendrites
- Decrease synaptic density in cortex
- Decrease myelination
- Neurofibrillary Tangles (Alzheimers) and neurtic plaques
What are the implications for histological changes?
- Dementia (65+: 5%, 75+: 20%, 90+: 35%, Nursing homes- 50%)
- Slower neural transmission that leads to Increase response/ reaction time
- procession input slower
- patterns of movement change
- Max degree of skill is less
What are cardiovascualar changes?
- Decrease resting BMR-due to decrease muscle mass and general mass
- Increase BP-decrease compliance in vessels
- Decrease max VO2-cellular changes in enzymes and ability to extract O2, as well as eventual cell loss
- Decrease blood flow and O2 delivery
- Decreased neurotransmitters
- Altered hormonal response especially with exercise
- Decreased neuromuscular response
What are the implications for cardiovascular changes?
- response to training is slowed and lower potential
- slower healing
- increase reaction time ->increase risk of falls
Musculoskeletal changes?
- Decrease in Type II fibers- increase atrophy and decrease %
- Decreased mass (lean muscle tissue)- 10%/decade and men lose more
- Decrease in water cells
- Decrease connective tissue elasticity-increased tears
- Collagent Alteration
- Increased fat mass gain (greatest rate of gain btwn 20 and 40 y/o)
- Bone density alterations (ratio of inorganic to organic; bone mineral content)
Musculoskeletal implications?
- decreased strength, power, functional activities -> increased risk of falls
- Decrease in muscle strains
- Decreased shock absorption
- Increased Fxs
What does a DEXA scan detect? What is a T-score?
- DEXA detects 1% change in bone loss
- T-Score compares to optimal gender
What do standard deviations of a T-score indicate?
- -1 = normal limits
- -1-(-2.5) = osteopenia
- <-2.5= osteoporosis
- <-2.5 w/hx of fx= severe osteoporosis
Definition of osteoporosis:
Reduction in quantity of bone or atrophy of skeletal tissue, resulting in bone trabeculae that are scanty and thin.
How much bone mass is lost before it pops up on x-ray?
30% +
How much bone mass can a person lose by 85 y/o?
up to 50%
How much height do you lose after the age of 40?
3%/ decade
What are the 2 types of osteoporosis?
- Type 1 = postmenopausal
- characterzied by loss of trabecular bone
- greatest loss first 5 years
- Type 2= involutional or senile
What are uncontrollable risk factors for osteoporosis?
- Fair-skinned or Asian woman
- Northern European ancestry
- Famlly hx of osteoporosis
- Small frame
- Post-menopausal, hysterectomy
Controllable risk factors of osteoporosis?
- underweight/chronic dieter (decreased estrogen)
- smoking
- inactivity
- excessive alcohol intake (2-3oz/day)
- 6 + cans of carbonated drinks/day (phosporous depletes calcium)
- High protein diet (eliminating cheese,meat, eggs decrease urinary Ca losses in half)
- Caffeine (lose Ca)
What causes secondary osteoporosis?
- Meds
- hyperparathyroidism
- diabetes
- Hyperthyroidism
- RA
- Ricketts
- Paget’s (bone tissue replace with immature bone cells)
- Polio
- SCI
- Corticosteroids
- Anticonvulsants
How do you treat/prevent osteoporosis?
- Weight bearing exercises
- Nutrition
- Calcium-1200mg/day for >50y/o
- Vitamin D- recommended daily 10 mcg for 51-70y/o; 15 mcg for >70y/o
- Avoid caffeine
What are the different types of meds to treat osteoporosis?
- Bisphosphanates (Fosamax)
- Calcitonin (Miacalcin)
- Raloxifene
- Extrogen
- Zeldronic acid (reclast or zometa)
What do biphosphanates do?
They help regulate calcium and prevent bone breakdown. They slow down the rate of bone breakdown by inhibiting osteoclasts
What does calcitonin do?
slow bone loss and decrease pain associated with osteoporosis fxs
What does raloxifene do?
It is a Selective Estrogen Receptor Modulator that increases bone mass and lowers cholesterol. it does not have the same effects on the uterine lining as HRT estrogen so it doesn’t need to be combined with progesterone
What does HRT estrogen do?
Increases bone mass after menopause and decrease the risk of osteoporosis and fxs. It needs to be combined with progesterone or it will increase the risk of uterine cancer
What does zeldronic acid do? What is the down side?
- Decreases risk of vertebral fx and hip fxs.
- increase risk of serious a-fib
What are pulmonary changes?
- Decreased vital capacity
- decreased maximal flow rates
- decreased strength of respiratory muscles
- decrease in elastic fibers in lungs
- decreased alveolar surface area
- decreased vital capacity, tidal volume
- increased stiffness of chest wall
- increased functional reserve capacity
- increased respiratory rate
What are hormonal changes?
- decreased estrogen and progesterone
- decreased testosterone
- decreased glucose tolerance
- decreased growth hormone
- increased insulin concentration
- reduced hormonal response to stress
What are genito-urinary changes and implications?
Changes
- reduced vasopressin
- decreased glomerular filtration rate
- increased atrial natrieurtic peptide
Implication
- increased frequency
what are integumentary changes?
- decreased functions of protrection, excretion, secretion, asbsorption, thermoregulation
- less turnover of epidermal cells
- lower numbers of keratinocytes and fibroblasts
- reduced hair and nail growth
- decreased vitamin D synthesis
- decreased density of langerhans cells
- decreased production of epideram thymocyte-activiating factor which enhances T-cell response leading to decreased in immune response
- increased fibrosis
- increased atrophy
