Download Physiology of Aging

Physiology of Aging
Dr. John Puxty
Queen’s University and Providence Care
[email protected]
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Learning Objectives
By the end of this section, the student will
appreciate the importance of
 physiological and psychological factors that
contribute to normal aging,
 the difference between normal aging and the
diseases of aging,
 contribution of age-related changes to clinical
presentation of disease in the elderly
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Normal Aging
Despite stereotype most of the elderly age well!
3
Normal Aging
Despite stereotype most of the elderly age well!
Most of our images are based on the frail sub-set
who frequently use medical services
4
Normal Aging
Despite stereotype most of the elderly age well!
Most of our images are based on the frail sub-set
who frequently use medical services
Generally normal aging in associated with a
reduction in functional reserve capacity in tissues
and organs
5
Normal Aging
Despite stereotype most of the elderly age well!
Most of our images are based on the frail sub-set
who frequently use medical services
Generally normal aging in associated with a
reduction in functional reserve capacity in tissues
and organs
At advanced age more common to see evidence of
impaired homeostasis and response to external
insults such as illness
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Temperature Regulation and Aging
7
Risk Factors for Hypothermia in Elderly
Decreased thermogenesis
Decreased vasoconstriction in response to cold
Decrease in intensity of shivering
Reduced insulation with less subcutaneous tissue
Medications eg Chlorpromazine
Socio-economic (nutrition, heating etc)
Co-morbidities including falls/immobility
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Risk Factors for Hyperthermia in Elderly
Decreased ability to sweat
Decreased ability to redirect heat
 reduced capacity for vasodilation peripherally
 modest ability to increase cardiac output
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Skin and Aging
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Skin and Aging
In general, the skin is drier, thinner, and wrinkled
Other age-related changes include:
 Loss of the inter-digitations between the epidermis and
dermis, leading to ease of tearing or breakdown
 Decline in the vascular supply
 Decline in the immune cells of the integument.
 Decline in the activation of Vitamin D.
Clinical consequences include:
 vulnerable to tearing, bruising, and breakdown.
 pressure ulcers (decubiti) more likely
 delayed response to topically-administered toxic agents.
 sunlight exposure results in premature age-related
changes in the skin.
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Age Related Changes in Immune System
Age related changes include:
 The thymus involutes with age
 T-cell immunity tends to decline
 Cytokine level and function may change
with age
 Humeral (B-cell) immunity declines with
age
 Changes in neutrophil function with
increased margination, reduced migration
to site of inflammation/infection and altered
phagocytosis.
 Autoantibodies increase with age.
Clinical Consequences
 Decline in cell mediated immunity may
result in TB reactivation and shingles
 Vaccine response may be impaired
 Altered presentation of infection
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Endocrine Changes with Aging
Described Age-related Change
Consequence
Change in GTT
Insulin resistance increase
Increased incidence DM
Decrease in ADH/vasopressin
response to osmotic stimuli
Risk of dehydration or
hyperosmolar state
Tendency to Thyroid dysfunction
Abnormal TFTs
Growth hormone, melatonin, and
DHEA, decline with aging
?
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Linking to our environment
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Sight and Aging
The Aging Eye
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Sight and Aging
The Aging Eye
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• Reduction of pupil size slows
adjustment to light changes
Sight and Aging
The Aging Eye
• Reduction of pupil size slows
adjustment to light changes
• Corneal surface flattens,
admitting less light into the eye
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Sight and Aging
The Aging Eye
• Reduction of pupil size slows
adjustment to light changes
• Corneal surface flattens,
admitting less light into the eye
• Reduced lens transparency
interferes with reception of
colour wavelengths
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Sight and Aging
The Aging Eye
• Reduction of pupil size slows
adjustment to light changes
• Corneal surface flattens,
admitting less light into the eye
• Reduced lens transparency
interferes with reception of
colour wavelengths
•Reduced blood supply and
radiation damage to retinal area
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Smell and Aging
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Hearing and Aging
• Eardrum and Ossicles
thicken and become less
flexible
• Loss of hair cells in the
organ of the corti
• Loss of cochlear
neurons
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21
Taste with Aging
Subjective decline in Taste
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Examples of Clinical Relevance
Older adults may need longer to adjust to changes in
lighting and may need increased contrast to facilitate
depth perception.
Loss of high frequency sounds, which include
consonants, make what is heard unintelligible, leading
to the frequent complaint, "I can hear you but I can't
understand what you are saying."
It is important to recognize that a response that does
not correspond to a question may relate to sensory,
rather than cognitive, impairment
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Cortical Changes and Aging
There is some selective loss in the number and size
of neurons.
Dendritic connections may decrease.
A number of neurotransmitters change, which may
result in neurotransmitter imbalances.
24
CT Scan Changes and Aging
The brain tends to decrease in size and weight
Ventricles
White Matter
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Memory and Aging
May have more difficulty with certain components of
memory.
Typically, older adults need more time to process
information,
May have difficulty coming up with names
spontaneously (retrieval) because of reduced ability
to “filter” distractants.
For healthy older adults, these changes represent
more inconvenience than significant functional
impairment.
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Sleep and Aging
Sleep patterns tend to change
 decrease in Stage IV (deep) sleep,
 an increase in Stage I (light) sleep,
 an increase in the number of night-time awakenings.
Subjective reduction in quality of sleep
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Sensation and Peripheral Nervous Function
Increased threshold observed for peripheral sensory
modalities
Nerve conduction time slows with age secondary to
loss of the myelin sheath
The net effect of these changes is a decrease in both
amount and speed of information conduction to and
from the spinal cord and higher centers
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Spinal Cord
Modest decrease in
number of cells in the
spinal cord
Other changes
represent disease
processes such as
degenerative disease
of the spine and
intervertebral disks
with compression of
the spinal cord and
entrapment of the
nerve roots.
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Neuromuscular Junction
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Neuromuscular Junction
reduction in the absolute
numbers of motor neurons
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Neuromuscular Junction
reduction in the absolute
numbers of motor neurons
distance between the
junctional axon and the
motor end-plate is
increased
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Neuromuscular Junction
reduction in the absolute
numbers of motor neurons
distance between the
junctional axon and the
motor end-plate is
increased
folds of the motor end-plate
are flattened
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Neuromuscular Junction
reduction in the absolute
numbers of motor neurons
distance between the
junctional axon and the
motor end-plate is
increased
folds of the motor end-plate
are flattened
the concentration of ACh
receptors at the motor endplate is decreased
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Neuromuscular Junction
reduction in the absolute
numbers of motor neurons
distance between the
junctional axon and the
motor end-plate is
increased
folds of the motor end-plate
are flattened
the concentration of ACh
receptors at the motor endplate is decreased
the amount and release of
ACh in the junctional
vesicles is decreased
35
Sarcopenia
Between ages 30 and 75:
lean body mass
decreases due to loss
of skeletal muscle
mass
number and size of
muscle fibers
progressively
decrease.
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Muscle Fibres and Aging - impact
Type I (slow twitch, aerobic) muscle fibers are resistant to age-associated atrophy,
at least until the ages of 60 to 70 years
Type II (fast-twitch, anaerobic) muscle fibers appear to decline with increased age
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Muscle Strength and Aging
decrease in the ability to maintain force production is
not so much a function of age as it is related to
muscle group location
the muscles of the lower extremity are better able to
maintain force output when compared to the muscles
of the upper extremity
research indicates that elderly muscle can adapt
positively, just like young muscle, to resistance
exercise.
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Vulnerability to Falls is partly result of:
Reduced sensory input
including propioceptive
information
Delayed nerve conduction
Reduced numbers of
motor neurons
Reduced fast twitch fibres
Reduced muscle mass
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Osteoporosis and Fractures
Normal
• Loss of endocrine
protection
• Reduced endogenous
production of Vitamin D
Life-Style Related
• Low dietary intake of
Calcium
• Disuse
Disease Related
• Chronic Renal Disease,
Rheumatoid Arthritis,
Thyroid Disease
• Medications – Steroids,
Thyroxine
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Cardiac Output and Age
No change at rest in
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
cardiac output

end-diastolic

end-systolic

volumes ejection
fraction
Summary of Cardiac Morphological Changes
Consequences:
•
Higher Systolic BP more
common
•
Trend towards diastolic
dysfunction
•
Reduced ability to
increase heart rate
•
Increased likelihood of
postural hypotension
Click to view animation of changes in cardiac morphology with aging
42
Age-related Respiratory Changes
Decreased chest expansion
 kyphoscoliosis
 calcification of intercostal cartilage
 arthritis of the costovertebral joints
Decreased elastic recoil of the lungs
Reduced diaphragm function
Increased airways obstruction
Reduced Vital Capacity
Increased Residual Capacity
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Consequences of Respiratory Changes
 Increased energy of
breathing
 Increased airways resistance
 Increased in dead-space
 Reduced V/Q ratio resulting
in a decrease in the partial
pressure of oxygen in blood
when breathing room air.
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Oropharyngeal
Modest change in taste
Modest reductions in submandibular and sublingual
gland secretions
Swallowing intact in normal elderly
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Gastric Function and Aging
Modest reduction
in fluid emptying
from stomach
Decline in gastric
secretions
Atrophic gastritis
more common
Prone to
increased pH
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Small Intestine and Aging
Modest Changes
in motility
Normal transit
time and
absorption in
absence of
disease
Pancreas shows
decrease in
overall weight,
duct hyperplasia,
and lobular
fibrosis
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Liver Function and Aging
Standard LFTs
unchanged
Microsomal
oxidation, has
been found to
be slowed with
aging
Metabolism
through
Cytochrome
P450 system
delayed
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Large Intestine Function and Aging
Changes in
motility
increase in
retropropulsion
increased transit
time
tendency to
constipation
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Glomerular Function and Aging
Decline in renal blood flow from 1200 mL/minute at age 30 to 40
years to 600 mL/minute at age 80.
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Tubular Function and Aging
Decline in ability to excrete concentrated urine
Delayed or slowed response to sodium deprivation or a sodium
load
Delayed or sluggish response to an acid load
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Male Specific Urogenital Changes
Decreased blood
flow may lead to
a decrease in
erectile function.
Sperm count
tends to decline
and chromosomal
abnormalities
tend to increase.
The prostate
increases in size,
and prostatic fluid
reduced.
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Female Specific Urogenital Changes
Reproductive
capacity is lost at
the time of
menopause.
Ovary, uterus,
and vagina tend
to atrophy
following
menopause.
Tendency to
“stress
incontinence”
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Summary of Normal Aging
Despite stereotype most of the elderly age well!
Most of our images are based on the frail sub-set
who frequently use medical services
Generally normal aging in associated with a
reduction in functional reserve capacity in tissues
and organs
At advanced age it is more common to see evidence
of impaired homeostasis and response to external
insults eg illness
54