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