L18 Physiology of Aging Flashcards
(34 cards)
When does aging begin?
After developmental stage
What is an accelerated ager, normal ager, and a super ager?
accelerated ager biological age is higher than the chronological age.
normal ager: biological age matches the chronological age
super ager: body ages very slow
What are the DRI age groups for over 50?
51 - 70
>70 years
What are the characteristics of aging?
- molecular and cellular changes
- a decrease in regeneration capacity
- changes in tissue, organ and system functions
- a decline in the ability to respond to stress and environmental stimuli (less likely to return to homeostasis)
What are the theories of aging?
- evolutionary
- genetic and protein dysfunction
- free radical damage
- cell senescence
One of the causes of aging is damage done to genetics. What are the 4 primary hallmarks of aging due to genetic damage?
genomic instability
telomere attrition
epigenetic alterations
loss of proteostasis
What causes genomic instability?
- genetic damage from exogenous and endogenous sources that reduce DNA repair mechanisms. Damaged DNA accumulate.
- some of these exogenous and endogenous sources are free radical reactive oxygen species (ROS). For example superoxide (O2-), and hydrogen peroxide (H202). They are generated mainly in the mitochondria and damage proteins, lipids, and DNA.
- there are some antioxidant enzymes that neutralize ROS. For example, superoxide dismutase, catalase, glutathione, and peroxidase (some require specific nutrients from the diet).
What are some nutrients and minerals that are important in antioxidant function?
*increasing the expression of genes producing antioxidants in some animals has resuted in longer life
copper
zinc
manganese
What is telomere attrition, one of the damages to DNA that causes aging?
- telomeres are a chromosomal part of the DNA that is easily damaged
- it is the loss of length in the telomere and the repeated repication of the shortening strand which leads to impaired cellular replication
- telomerase repairs the damage
- cancer cells have high telomerase so too much can be problematic
What is an epigenetic modification, one of the damages to DNA that causes aging?
- they occur throughout the lifespan from numerous methods (histone modification, DNA methylations, ect.)
- it is an adaptive response in gene expression
How does the dysregulation of protein homeostasis contribute to aging?
- proper protein folding is important for proper protein function
- aging is associated with a loss of the repair mechanisms and accuulation of misfolded and unfolded proteins
- mechanisms for protein folding: lysosome autophagy, ubiquitome-proteasome pathway, heat shock protein mediated folding
What are 3 of the body’s responses to cell damage related to the aging process?
- deregulation of nutrient sensing
- mitochondiral dysfunction
- cellular senescence
Explain the deregulation of nutrient sensing, the body’s response to cell damage
- damage to cells can cause a downregulation of nutrient sensing pathways that use anabolic pathways for functioning ??
Explain mitochondrial dysfunction, one of the body’s responses to cell damage?
- the mitochondiral turnover rate is reduced which leads to an increase in cell damage (ie. there is an increase in ROS causing damage, oxidative damage to proteins, changes in lipid membranes, telomere attrition, destabilization of respiratory chain complexes)
- endurance training and dietary restrictions are known to reduce mitochondrial damage
Explain cellular senescence, one of the body’s reponses to cell damage.
- cell senescence is when the cells stop replicating. This process prevents the replication of damaged cells and triggers the removal of damaged cells by an immune response.
- can be naturally caused by aging, telomere attrition, and DNA damage
- This is a positive function in the young but in the old, there is an accumulation of senescent cells or a decrease in clearance of senescent cells causing inflammation, and decreases tissue function, stem cell exhaustion, ect, and ultimately aging.
One of the effects of cellular senscence is stem cell exhaustion. What does this effect in the body?
anemia, myelodydisplasia, osteoperosis, decreased fracture repair, decreased repair of muscle fibres, and decreased intestinal function.
What are some oral, vision, olfactory, dental changes that occur with aging?
- teeth become ore brittle
- changes in tooth and mouth mucosal tissue structure
- reduced saliva
- reduced function of sensory cells (sight, smell, touch, taste)
- all of these can impact food intake
What are some gastrointestinal changes that occur with aging?
- there is slower motility which delays stomach emptying
- in the stomach, there are some changes that can affect digestion and absorption of nutrients. For example, decreased nitric oxide, increased stretch, and atrophic gastritis.
- reduced absorption of nutrients in the small intestine
- liver decreases in size and decreases blood flow which results in lower detoxification ability
- impacts satiety and nutrient needs
What are some skeletal and muscle changes that occur with aging?
- There is a decrease in size and number of muscle fibres (type 2 more than type 1)
- reduced innervation
- lowered muscel strength (upper body more than lower body)
- sarcopenia nd disability
What are some bone changes that occur with aging?
- resorption is greater than formation
- osteoclasts have greater function than osteoblasts
- loss of mineral density and protein, as well as changes in mineral crystal properties
- accumulation of microfractures
- can result in a loss of height and increased risk of microfractures
What are some cardiovascular and pulmonary changes that occur with aging?
- decreased muscle fibres and hypertrophy
- lower heart rate and maximal output
- increased vascular resistance
- reduction in lung function and VO2 max
- loss of diaphram and inter-rib muscle strength, changes in chest wall
- alterations in ability to perfom activity
What are some renal changes that occur with aging?
- there is a reduced number of nephrons, slowed filtration rate, and decreased blood flow
- the kidneys usually maintain normal function but they are slow to rspond to sudden changes
- can impact fluid and electrolyte balance
How does the skin change with age?
- thinning of the skin layers
- changes in collagen structure: superficial laxity
- irregular pigmentation
- reduction in 7-dehydrocholesterol (precurson to vitamin D when exposed to sunlight)
What is the precursor to vitamin D and what age groups may need a supplement?
- infants need vitamin D supplement
- 50+
