Topic 10: Ageing

Question 1

Briefly describe 4 common theories of ageing in the human body

Answer 1

1. Wear and Tear - cell death, altered genes, DNA damage
2. Mitochondrial/Oxidative - free radical theory; damaged radicals; oxidative damage
3. Genetic - cellular senescence linked to telomere function and shortening of telomeres after each division
4. Immune - increased infection, production of auto-antibodies and decreased response to vaccines, immune system function

Question 2

Briefly define the following terms: Cellular senescence, Replicative senescence, Stress-induced
premature senescence

Answer 2

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)

Question 3

Briefly explain the consequences of vascular ageing on resting blood pressure and cardiac
structure/function.

Answer 3

Reduced compliance and augmented transmission of pressure + velocity to periphery causes elevated SBP and cardiac hypertrophy

Question 4

Summarise briefly the effects of age on cardiac structure and function

Answer 4

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

Question 5

Briefly describe the age–related functional changes in the pulmonary system in terms of: chest wall
compliance; lung elastic recoil & respiratory muscle strength.

Answer 5

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

Question 6

• Summarise the physiological impact of these age related changes in lungs.

Answer 6

• • 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

Question 7

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.

Answer 7

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

Question 8

• Summarise the physiological impact of these age related changes in kidneys.

Answer 8

Ageing can affect glomeruli, tubulointerstitium and vessels - more susceptable to diseases

Urinary albumin excretion increases with age

Question 9

• Summarise the impact of ageing on common metabolic functional parameters.

Answer 9

DECREASED

• metabolic rate
• lean body mass
• total body water
• muscle mass

INCREASED

• % body fat
• insulin resistance

Question 10

• Summarise the impact of ageing on common metabolic functional parameters.

Answer 10

DECREASED

• metabolic rate
• lean body mass
• total body water
• muscle mass

INCREASED

• % body fat
• insulin resistance
• frequency of dehydration, hypernatremia, hypokalemia, acidosis