Lecture 3 - Homeostasis in Aging Flashcards
Definition of Homeostasis
The tendency toward a relatively stable equilibrium between interdependent elements, especially as maintained by physiological processes
Principles of Homeostasis in the Elderly
- Homeostatic balance will be less optimal, and reached more slowly, with age
- Decreased cellular function (rate and efficiency) secondary to accumulation of lipofuscin and secondary lysosomes
- Drugs and homeostatic mechanisms change with change in body composition, particularly a decrease in total body water
Homeostasis changes in the CNS
- cerebral atrophy
- Decreased blood flow
- Decreased myelin and total brain lipid
- Altered neurotransmitter concentration (dopamine and serotonin)
- Slowed mentation
- more difficulty in forming new memories
- Mood, circadian, and concentration changes
- Increased delicacy of epidural vessels
- Brain shrinkage
Increased risk of risk of intracranial bleeding to minimal trauma
Endocrine System Homeostasis (cause and then effect)
- Decreased T3- Occult hypothyroidism
- Gradual beta cell senescence and increased tissue resistance to insulin - increased fasting glucose and glucose intolerance
- Marked decrease in DHEA and Sex hormones- Osteoporosis, decreased libido, corticosteroid reserve
- Decreased plasma renin and aldosterone- Predisposition to hyperkalemia
- Increased NE, vasopression, insulin, ANP, and parathormone - Impaired extracellular volume regulation and electrolyte homeostasis
Cardiovascular System Homeostasis changes (cause then effect)
- Decreased responsiveness to beta-adrenergic stimulation- normal resting heart rate but diminished maximal heart rate
- Decreased baroreceptor response- Increased risk of orthostatic hypotension (falls)
- Increased collagen deposition and cross linking - increased SBP (stiff pipes) and afterload- BIG DEAL- LEADS TO ARTERIAL STIFFNESS
- Decreased cariocytes and increased fibroblasts- impaired LV relaxation (diastolic dysfunction)
- Diastolic dysfunction- Increased reliance on atrial kick (esp. in A. fib)
- Marked dropout of pacemaker cells in SA node- Increased risk of atrial fibrillation
- Deterioration of conductive cells in SA/AV/His/Purkinje system- Increased risk of heart block
How does a geriatric patient increase cardiac output during times of increased oxygen requirements?
Stroke volume must increase- this is a conundrum. In younger people you can simply increase heart rate a great deal- but in old age, the main factor has to be the stroke volume!
Pulmonary System Homeostasis Changes (cause and then effect)
- Increased collagen deposition and cross linking –> increased arterial stiffness- decreased lung elasticity, decreased FVC and FEV1
- Accumulated effects of oxidative stress/free radical damage - loss of alveoli and total alveolar surface area- and thus maximal oxygen uptake
- Reduced diaphragmatic strength- reduced tidal volume, V/Q mismatch
GI System Homeostasis Changes (cause then effect)
- Slowed colonic transit time - Constipation
- Increased hepatocyte accumulation of lipofuscin and secondary lysosomes- Reduced metabolism, clearance of drugs
Renal/Urinary System Homeostasis Changes (cause then effect)
- Decreased renal mass, GFR, renal tubular secretion and concentrating ability, and bladder capacity- Decreased creatinine clearance, decreased drug clearance
- Gradual hypertrophy of prostate secondary to continuous testosterone exposure- BPH with obstruction and Carcinoma of Prostate risk
Muscoloskeletal System Homeostasis Changes (cause then effect)
- Mechanical wear and tear of articular cartilage- arthritic pain, loss of ROM and stability
- Gradual lengthening of tendons, ligaments, and fascia- increased laxity of joints, flattening of arch of feet
- Decreased muscle mass and lean body mass- sarcopenia, weakness, increased fall risk
- Negative calcium balance in both sexes, decreased bone mass- osteoporosis, loss of height, increased curvature of spine, decreased muscle strength for breathing, and gait impairment
Osteoporosis- definition
Decreased bone density secondary to decreased calcification (decreased osteoblastic activity vs. increased osteoclastic activity
Effect of fluoride as a treatment for decreased bone density
It DOES increase bone density, but it increases cortical, not cancellous density, leading to “chalky bone” that is more prone to fracture.
What is working as a good treatment for osteoporosis
Prolonged exogenous estrogen therapy
Skin Homeostasis Changes (cause and effects)
- Decreased vascularity of dermis, decreased total body water- Dry skin, greater risk of tearing and injury
- Altered epidermal turnover time - prolonged wound healing
- Decreased melanocytes- uneven tanning
- Low dermis density, reduced subcutaneous adipose and eccrine function- poor insulation, decreased sweating response
- Hair loss- decreased self esteem
Vision Homeostasis Changes (cause and effect)
- Increased rigidity of iris, decreased size of the anterior chamber- Decreased size of pupils, impaired adaptation to variable lighting
- Accumulation of yellow substance in the lens- alteration of color perception
- Decreased elasticity and cloudiness of lens (cataracts)- significant impairment of vision in presence of glare and low light conditions; falls; global impairment
