ageing

• Age


  Adulthood = age 20 to death

  • Young adulthood
  • Middle aged
  • Older adult

  Ageing: the process of ageing

  Senescence: the process of deterioration with age
• Why do we age?

  Our cells constantly divide to replace and build

  • The chromosomes in those cells become damaged and deteriorate, therefore our new cells are not what they used to be

  Free radical theory of ageing

  • Free radicals can alter the structure of molecules resulting in damage/dysfunction

  Decline of mitochondrial DNA

  • Results in aaa decline in ATP production

  Immune system becomes less efficient

  Genetic traits

  Reduced ability to maintain homeostasis
• Causes of ageing


  Complex and multifactorial. Three stages of ageing:

  • Basic homeostasis
  • Decrease in organ mass
  • Decline in function

  Behavioural adaptations
• Ageing and the cardiovascular system

  Reduction in arterial elasticity:

  • = increased stiffness of arteries and aorta -> = left ventricular hypertrophy
  • Can cause an increase in increased pulmonary capillary pressure = out of breath when exercise

  Cardiac tissue

  • Accumulation of lipids and collagen = increase in cardiac muscle stiffness and less compliant

  Heart valves becomes less flexible

  • Primarily the semilunar valves = abnormal functioning

  SA node cells decrease, electrical activity alters
• Ageing and the cardiovascular system

  HR:

  • Maximum heart rate declines, 220-age
  • Response to epinephrine and norepinephrine declines

  SV:

  • Can decline due to heart being less compliant therefore less blood being ejected
  • Can also stay the same

  CO

  • Declines with age

  VO2

  • Declines from age 50 - increased fat tissue, decrease CO, decrease in physical activity
• Ageing and the respiratory system

  Vital capacity decreases dues to weakened respiratory muscles and decreased thoracic cavity compliance from the stiffening of cartilage and ribs:

  • Decreased ability to fill lungs = inspiratory reserve volume decrease
  • Decreased ability empty lungs = expiratory reserve volume decreases
• Ageing and the respiratory system

  Residual volume increase:

  • Dead space increases due to bronchioles and alveolar ducts expanding and loss of elasticity

  Decreased gas exchange across respiratory membrane:

  • Alveolar walls are reduced (decreased surface area) and thickened

  Gradual rise in tidal volume

  Mucus builds up:

  • Cilia decrease in number and movement
• Ageing and the urinary system

  • Kidneys decrease in size
  • Amount of blood flowing through decrease
  • Afferent and efferent arterioles twist and become irregular
  • Glomeruli are destroyed - by 80, 40% are not working
  • Nephrons and collecting ducts structure alters by becoming shorter, thicker and irregular
  • The ability to secrete and absorb declines = ability to produce concentrated urine declines - decreases ability to rid toxins and increased risk of dehydration
  • Loss of responsiveness to ADH and aldosterone
  • Decreases in renin secretion
• Ageing and the digestive system

  Thinning of the mucosa and submucosa:

  • Less mucus secreted

  = reduced protection from toxins from the outside

  = reduced ability of the liver to detoxify

  = susceptibility to infections

  Decrease in blood supply

  Decrease in smooth muscle cells

  • Reduced mobility

  Less secretions from major secretory organs

  Muscles of mastication are weakened

  • Less mechanical digestion
• Ageing and the endocrine system

  Gradual decrease in secretory activity in some glands. This maybe secondary to a general decline in physical activity.

  • GH levels decrease - may explain the decline in muscle and bone mass in older persons, greater in those that don't exercise
  • Thyroid hormone crease slightly - may be because of a decline in lean body mass. Damage by the immune system due to ageing. May also occur and cause a decline in T3 and T4 production
• Ageing and the endocrine system

  • Increase in parathyroid hormone but reduced blood levels of CA2+ due to reduced dietary intake = loss of bone matrix to maintain blood levels
  • Thymus gland secretes thyroxin = development and maturation of the immune system - secretion decreases with age causing a reduced efficiency go the immune system and subsequent increase in susceptibility of infection
• Ageing and thermoregulation


  Sweat gland secretions decrease

  Reduced peripheral blood flow

  • Reduced ability to regulate temperature

  Increase risk of heat exhaustion and illness