Physiology of Aging

Question 1

Notes on cardiovascular system and aging

Answer 1

• Cardiac output decreases 1%/annum after 3rd decade
• Cardiac muscle → decreased inotropic response to catecholamines, decreased response to cardiac glycosides
• Atheroscleosis earlier in the aorta and carotids than in coronary, cerebral, peripheral vessels
• Physiological changes
  
  • Degeneration of conducting tissues (collagen deposition, atrial fibrosis, reduced pacemaker cells)
  • Myocardial hypoertrophy, increased LV wall thickness, increased LA size
  • Blunted baroreflex reponse → tendancy towards syncope
  • Reduced diastolic relaxation
  • Reduced post synaptic adrenergic responsiveness → reduced HR response to stress and respiration
  • Autonomic impairment → postural hypotension

Question 2

Notes on respiratory system and aging

Answer 2

• Lung volume
  
  • Decrease vital capacity
  • TLC remains constant - residual volume increases
  • Reduction in FEV1 and FVC
• Gas exchange
  
  • Arterial oxygen pressure decreases. Alveolar oxygen tension constant. → increased A-a gradient. Due to mismatch of ventilation and perfusion
  • Ventilatatory response to decline PaO2 and increasing PaCO2 blunted
  • Decrease in elastic recoil of lungs → greater tendancy for airways to collapse

Question 3

Notes on genito-urinary system and aging

Answer 3

• Reduction in renal size (more cortical loss)
• Decline in glomeruli → decrease in creatinine clearance
• Tubular function decreases
• Increased distal tubular diverticula (predisposing to pyelonephritis)
• Reduction in renal blood flow
• Variable reduction in urinary bladder capacity and contractility, detrusor hyperactivity → frequency, incontinence, nocturia

Question 4

Notes on gastrointestinal system and aging

Answer 4

• Oesophagus → decreased peristaltic response, increased non-peristaltic response, delayed transit time, decreased relaxation of lower sphincter → dysphagia, voluntary curtailment of caloric consumption (→ weight loss)
• Stomach → atrophic gastritis
• Colon → decrease in intestinal motility → constipation

Question 5

Notes on liver, biliary tract and aging

Answer 5

• Liver decreases in weight after 50 years
• Liver function does not change
  
  • Some drugs metabolised slowly by liver (diazepam) due to decrease in smooth endoplasmic reticulum
  • Reduced activity P-450 enzyme - change in drug levels
• Albumin does not drop in well elderly

Question 6

Notes on neurological system and aging

Answer 6

• Cortical atrophy occurs with age (white > grey matter). Reduction in cerebral blood flow and oxygen consumption → increased risk of delirium, long recovery times to baseline function after illness
• Reduced number dopamine receptors, increased alpha adrenergic response, increased muscarinic parasympathetic response
  
  • Parkinsonian symptoms
• Loss of neurones in both brain and spinal cord → depression (can be result of impaired synaptic activity)
• Reduction in beta adrenergic responsiveness and receptos → reduced response to beta blockers, tendancy towards syncope, exaggerated response to anticholinergic drugs