The Physiology of Aging1

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The Physiology of Aging1

  1. 1. The Physiological & Psychological Impact of Ageing Part I Systemic Impact
  2. 2. Structure of Lecture 1. Cardiovascular system 2. Respiratory System 3. Musculo-skeletal system 4. Nervous system
  3. 3. 1. Cardiovascular system
  4. 4. 1. Cardiovascular system Main functions in homeostasis: • Transportation of materials around the body - useful products to cells - harmful by-products away • Defence mechanisms - removal of dangerous chemicals • Temperature control - dermal blood vessels • Acid/Base Balance - optimal pH 7.35-7.45
  5. 5. The Heart
  6. 6. <ul><li>Deposits of collagen and fatty tissue into heart muscle. </li></ul><ul><li>Walls of arterioles = thicker with less elasticity. </li></ul><ul><li>Longer time between diastole and systole of heart muscles. </li></ul><ul><li>Decreased cardiac output (1/3 less Oxygen from 20-80 years). </li></ul><ul><li>More difficult to do strenuous exercise. </li></ul>Ageing changes of the Heart
  7. 7. Cardiac Output (CO) = Stoke Volume (SV) x Heart Rate (HR) The Cardiac Cycle Cardiac Cycle
  8. 8. Blood Pressure Changes Associated with Ageing • 40% of the elderly have systolic pressure above the safe maximum (160 mmHg) • Systolic Blood Pressure -  5-8 mmHg per decade after 40-50 yrs - in females systolic BP stops rising after 70 yrs • Diastolic Blood Pressure -  1 mmHg per decade
  9. 9. Pulmonary Congestion • Induced by blood remaining in the left ventricle after contraction. • Inhibits blood flow from the lungs & raises blood pressure in the lung capillaries which forces fluid out of the capillary walls • This PULMONARY OEDEMA reduces respiratory function and causes individuals to feel out of breath more quickly.
  10. 10. Coronary Artery Disease • The older heart requires more oxygen to pump the same amount of blood around the body as a young heart. • This is not important as long as the coronary arteries remain normal. • However, age changes cause deficiencies in the normal functioning of coronary arteries. • ATHEROSCLEROSIS prevents adequate blood supply to the heart. • This causes MYOCARDIAL INFARCTION
  11. 11. Coronary Arteries
  12. 12. Age Changes in Arteries • Loss of elasticity - accumulation of calcium & lipids - breakage of elastic fibres This loss of elasticity means that vessels are less able to be stretched by blood flow. -  systolic blood pressure
  13. 13. • Widening & Lengthening At first this compensates for elasticity loss but fibres are eventually stretched until they stretch no more. Each heart contraction causes a rapid and dramatic rise in systolic BP This leads to increases in cardiac O 2 demand • Diminished Elastic Recoil Causes slowing of blood flow through arteries
  14. 14. ATHEROSCLEROSIS • Most common form of arterial disease forming one of a group of arterial diseases known as ARTERIOSCLEROSIS. • Causes the formation and enlargement of scar like material called PLAQUE in the walls of arteries. • Plaque cases arteries to narrow and thus reduces blood flow. • It also causes stiffening of the arteries reducing their ability to dilate when oxygen demands in crease.
  15. 15. Age Changes in Arteries
  16. 16. • Atherosclerosis also involves roughening of the inner lining of arteries and exposure of underlying collagen. • Both of these factors promote the formation of clots which can impede and totally block blood flow. • Atherosclerosis causes: - heart attacks - strokes - aneurysms - kidney disease - muscle problems in the legs
  17. 17. Mechanisms Promoting Atherosclerosis • Endothelial Dysfunction • Free Radicals - formation of lipid peroxides • Blood Low Density Lipoproteins (LDLs) - eg cholesterol & triglycerides • Elastase - an enzyme that breaks down elastic fibres • Glycation - the use of glucose to form cross links between protein molecules - produces age-related glycation end products (AGEs) and FRs
  18. 18. Risk Factors in Atherosclerosis <ul><ul><li>Smoking </li></ul></ul><ul><ul><li>Blood pressure </li></ul></ul><ul><ul><li>High blood LDLs </li></ul></ul><ul><ul><li>Diabetes Mellitus </li></ul></ul><ul><ul><li>Family history </li></ul></ul><ul><ul><li>Advancing age </li></ul></ul>
  19. 19. Age Changes in Capillaries • Become narrower and irregular in shape • Decrease in number • Walls become thicker • Decreased permeability • Reduce the ability of the circulatory system to adjust quickly to changes in the demands of the body
  20. 20. Age Changes in Veins • Thickening of the walls and valves • Varicose veins -  vein diameter - promotes clot formation thrombus  embolus
  21. 21. 2. The Respiratory System Main functions for homeostasis: • Gaseous exchange - obtaining 0 2 & eliminating CO 2 Ventilation (breathing) Perfusion (pulmonary circulation) Diffusion (0 2 in & CO 2 out)
  22. 22. Age Changes Affecting Ventilation • Narrowing of Bronchioles • Decreased alveolar surface area • Respiratory muscles become weaker • Decrease in lung elasticity <ul><li>Consequences: </li></ul><ul><li>Rate at which air can circulate through the system </li></ul><ul><li>Ventilation is made more difficult and this  0 2 supply </li></ul><ul><li>and  CO 2 in the blood. </li></ul>
  23. 23. Ventilation Minute Volume = Vol. Per breath x breaths per minute Vital Capacity = Tidal Volume + Inspiratory Reserve Vol + Expiratory Reserve Vol. VC = TV + IRV + ERV Total Lung Capacity = TV + IRV + ERV + Residual Vol. (TLC) (RV) 6.0 litres 2.7 2.2 1.2 0
  24. 24. • Ageing does not affect the TLC but does affect the volumes of air that can be moved. • The loss in elasticity of the lungs leads to  IRV & ERV • Tidal volume increases and there are increases in residual volume • The vital capacity of the lungs decreases • These volume changes have two effects: 1) decrease in maximum minute volume. 2)  VC with  RV means less fresh air is inspired. This  rate of diffusion.
  25. 25. Diseases of the Respiratory System • Respiratory diseases (excluding lung cancer) are the fourth leading cause of death in the elderly. • Lung cancer • Chronic Bronchitis - inflammation of the bronchioles -  mucous production  ventilation by making airways narrower • Emphysema - destruction of parts of the the lungs e.g. bronchioles & alveoli • Pneumonia - inflammation of the lungs  infection
  26. 26. 3. Musculo-Skeletal System Main functions in homeostasis: - movement - support - heat production - protection - mineral storage - blood cell production
  27. 27. Age changes in muscles •  nerve-muscle interactions •  muscle mass •  blood flow in muscles Consequences •  Reaction Times (RTs) •  speed of movement •  endurance
  28. 28. Skeletal Age Changes • Loss of bone matrix (more extensive in post menopausal females) OSTEOPOROSIS • Stiffening of hyaline Cartilage between joints due to loss of H 2 O and Ca 2+ deposition. OSTEOARTHRITIS Consequences • Generalised weakening of the bone (falls tend to cause more fractures in elderly) •  joint mobility
  29. 29. 4. Nervous System Main functions for homeostasis: • monitoring • communication • stimulation • memory • information processing
  30. 30. Age Changes in the Nervous System • Loss of brain volume •  neurotransmitters, slower nerve conduction rate. •  numbers & changes in the structure of synapses •  numbers of motor neurons • slower reflexes
  31. 31. • memory loss -  short term memory (STM) - greatest decline in STM is for information presented verbally and quickly. - long term memory is largely unaffected • increase reaction time (  accidents?) • vocabulary & conversation • sleep pattern changes. • personality changes?
  32. 32. Diseases of the Nervous System Cerebro-Vascular Accidents (CVAs) or Strokes • third leading cause of death in the over 65 age group • occur when blood supply to the brain is disrupted - common result of atherosclerosis - hypertensive haemorrhagic stokes • Effects depend upon the site of blockage/leakage in the brain: - paralysis/paresis - loss of language skills - visual field defects
  33. 33. Dementias A broad category of diseases which involve a serious decline in memory and a decline in at least one other major function. - sufferers cannot carry out normal activities - difficulties must be experienced on a long term basis - caused by an identifiable physical abnormality • Number and rate of dementia cases are  • Incidence rate rises exponentially with age • Effects:  STM, loss of motor function, personality changes
  34. 34. Alzheimer’s Disease (AD) • Fifth leading cause of death in the US • AD is becoming a more important factor of ageing as risks of heart disease & cancer decline • Early onset or familial AD Late onset or senile dementia of the Alzheimer type • Causes: Genetic abnormalities? Normal part of the ageing process ? • Changes in the brain: senile plaques  beta amyloid neurofibrillar tangles  dead neurons low levels of acetylcholine

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