Age-Related Changes in Biological Systems

Age-Related Changes in Biological Systems

• Cardiovascular:

  • Thickening of the left ventricle wall, leading to a less efficient heart.
  • Reduced and irregular heartbeats.
  • Reduced elasticity of arteries.
  • Older individuals require more effort to pump blood.

• Digestive:

  • Weakened esophageal contractions and sphincter.
  • Reduced stomach elasticity, leading to earlier feelings of fullness.
  • Increased susceptibility to lactose intolerance.

• Endocrine:

  • Reduced reproductive hormones and thyroid hormone.
  • Insulin resistance, increasing diabetes risk.
  • Men experience a 1% annual decrease in testosterone.

• Immune:

  • Increased vulnerability to infections.
  • Increased autoimmune responses.
  • Reduced responsiveness to vaccinations due to decreased antibody production.
  • Reduced T-cell count, which is responsible for destroying pathogens.

• Nervous:

  • Reduced visual, auditory, and tactile acuity.
  • Decreased olfactory (smell) and gustatory (taste) sensitivity.
  • Structural and functional changes in the brain.
  • For example, the yellow color becomes less transparent with age.

• Integumentary:

  • Thinning of the epidermis, dermis, and subcutis.
  • Reduced skin elasticity.
  • Decreased ability to filter UV radiation.

• Musculo-skeletal:

  • Reduced bone density and muscle mass.
  • Increased rigidity of ligaments and tendons.
  • Thinning of cartilage.
  • By age 75, approximately 50% of body mass can be lost.

• Reproductive:

  • Menopause in women.
  • "Andropause" in men, characterized by changes in sexual functioning.
  • Men may experience longer erection times, reduced ejaculate volume, etc.

• Respiratory:

  • Reduced peak airflow.
  • Decreased gas exchange.
  • Increased breathlessness.

• Urinary:

  • Reduced kidney size.
  • Increased bladder rigidity and decreased capacity.
  • Urinary incontinence (uncontrolled urine leakage).

Brain Changes with Age

• Structural Changes:

  • Brain atrophy occurs with age:
    • Decrease in volume by 0.2% annually after age 35 and 0.5% after age 60.
    • Shrinkage of gyri (outward folds) and widening of sulci (inward folds).
    • Shrinkage of specific brain regions, particularly the prefrontal cortex, hippocampus, and cerebellum.
  • Deterioration of grey matter (neuronal cell bodies) involving loss of neurons, dendrites, and synapses.
  • Deterioration of white matter (neuronal axons insulated by myelin).
  • Enlargement of cerebral ventricles (fluid-filled cavities).
  • Decreased grey and white matter allows ventricles to expand.
  • Changes in cerebral vasculature (e.g., reduced blood flow in specific regions).
  • Loss of microglial cells (responsible for inflammation and debris removal).

• Note: Some research suggests that brain changes may be influenced by "covert" brain disease or cardiovascular risk factors, leading to "secondary aging" rather than primary aging.

• Functional Changes:

  • Neurotransmitter Systems:
    • Dopamine:
      • Associated with attention, memory, movement, reward/reinforcement.
      • Produced in the substantia nigra and ventral tegmental area (VTA).
      • Functionality decreases with age.
      • Significant losses in dopamine receptors, synthesis capacity, and transporters.
    • Serotonin:
      • Associated with mood, feeding, sleep, sexual behavior.
      • Produced in the raphe nuclei.
      • Functionality decreases with age.
      • Decreases in serotonin receptors, synthesis capacity, and transporters.