Briefly describe 4 common theories of ageing in the human body
- Wear and Tear - cell death, altered genes, DNA damage
- Mitochondrial/Oxidative - free radical theory; damaged radicals; oxidative damage
- Genetic - cellular senescence linked to telomere function and shortening of telomeres after each division
- Immune - increased infection, production of auto-antibodies and decreased response to vaccines, immune system function
Briefly define the following terms: Cellular senescence, Replicative senescence, Stress-induced
premature senescence
Cellular senescence =
- normal cells in culture didn’t proliferate indefinitely - division rate slows and ceases. Characteristic and function changes; loosing orginal shape, volume increases, flattened cytoplasm. Changes in nuclear structure, gene expression, protein processing and metabolism
Replicative senescence =
- when intracellular contact is lost and cells attached to the extracellular matrix, changes may alter tissue structure and function; extensive number of cell divisions
Stress-induced
premature senescence=
- stressors in response to rapid independant cell division (radiation, oxidative stress, lack of nutrients)
Briefly explain the consequences of vascular ageing on resting blood pressure and cardiac
structure/function.
Reduced compliance and augmented transmission of pressure + velocity to periphery causes elevated SBP and cardiac hypertrophy
Summarise briefly the effects of age on cardiac structure and function
30-50 yrs = 10% of muscle tissue is replaced by fibrous connective tissue and adipose tissue
50-80 yrs = 40% of mussle is replaced
Consequences =
- muscle strength/flexibility decrease
- slow reflexes
Briefly describe the age–related functional changes in the pulmonary system in terms of: chest wall
compliance; lung elastic recoil & respiratory muscle strength.
chest wall compliance =
- reduced chest wall compliance; calcification and other changes in the rib cage and itts articulations
lung elastic recoil =
- static elastic recoil pressure declines by 0.1-0.2 cmH20/year
- changes in spatial arrangement/ cross linking of elastic fibres network contribute
respiratory muscle strength.=
- impaired by age related modifications of the rib cage, decreased chest wall compliance and elastic recoil of the lung and muscle strength
- intercostal muscles are less able to contribute to ventilation
- changed related to nutritional status, energy metabolism
• Summarise the physiological impact of these age related changes in lungs.
- decreased lung elastic recoil
- increased residual volume and FRC
- decrease PaO2
- decrease FVC and forced expiratory flows
Loss of elasticity, increased energy cost, reduced gas exchange, and impaured vent/perfusion matching
Briefly describe the age-related structural and function changes in the kidney in terms of: glomerular
changes; arterioles; tubules, glomerular filtration rate; renal blood flow; and renin- angiotensinaldosterone profile.
glomerular
changes =
- less intact glomeruli, higher sclerotic gomeruli (atheroscleortic state)
arterioles =
- slcerosis of cortical systems and formation of direct channels between afferent & efferent arterioles in medulla
tubules =
- rreduced functioning tubules & length of proximal tubule; fibrosis, atrophic tubules
glomerular filtration rate =
- declines by 1 ml/min of age over 40 years
- av. decrease of 130 to 80 ml (30-80 years old)
- rate of decline accelerates after 65 years
renal blood flow =
- decreases with age
renin- angiotensinaldosterone profile =
- reduced GFR shifts in the RAAS
- lowered plasma renin levels, lowered renal Ang II levels
- reduced aldosterone levels in plasma
• Summarise the physiological impact of these age related changes in kidneys.
Ageing can affect glomeruli, tubulointerstitium and vessels - more susceptable to diseases
Urinary albumin excretion increases with age
• Summarise the impact of ageing on common metabolic functional parameters.
DECREASED
- metabolic rate
- lean body mass
- total body water
- muscle mass
INCREASED
- % body fat
- insulin resistance
• Summarise the impact of ageing on common metabolic functional parameters.
DECREASED
- metabolic rate
- lean body mass
- total body water
- muscle mass
INCREASED
- % body fat
- insulin resistance
- frequency of dehydration, hypernatremia, hypokalemia, acidosis
