Age-Related Changes in Biological Systems

Study Notes

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.

Description

This quiz delves into the various biological changes that occur as individuals age, focusing on key systems such as cardiovascular, digestive, endocrine, immune, and nervous. It highlights the impact of aging on heart function, digestion, hormone levels, immunity, and sensory acuity. Test your understanding of these physiological changes and their significance in the aging process.