The Physiology of Aging1
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Transcript of The Physiology of Aging1
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The Physiological & Psychological Impact of Ageing
Part I Systemic Impact
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Structure of Lecture
1. Cardiovascular system
2. Respiratory System
3. Musculo-skeletal system
4. Nervous system
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1. Cardiovascular system
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1. Cardiovascular system
Main functions in homeostasis:
• Transportation of materials around the body- useful products to cells- harmful by-products away
• Defence mechanisms- removal of dangerous chemicals
• Temperature control- dermal blood vessels
• Acid/Base Balance- optimal pH 7.35-7.45
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The Heart
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Deposits of collagen and fatty tissue Deposits of collagen and fatty tissue into heart muscle.into heart muscle.
Walls of arterioles = thicker with less Walls of arterioles = thicker with less elasticity.elasticity.
Longer time between diastole and Longer time between diastole and systole of heart muscles.systole of heart muscles.
Decreased cardiac output (1/3 less Decreased cardiac output (1/3 less Oxygen from 20-80 years).Oxygen from 20-80 years).
More difficult to do strenuous More difficult to do strenuous exercise.exercise.
Ageing changes of the Heart
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Cardiac Output (CO) = Stoke Volume (SV) x Heart Rate (HR)
The Cardiac Cycle
Cardiac Cycle
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Blood Pressure Changes Associated with Ageing
• 40% of the elderly have systolic pressure above thesafe maximum (160 mmHg)
• Systolic Blood Pressure
- ↑ 5-8 mmHg per decade after 40-50 yrs
- in females systolic BP stops rising after 70 yrs
• Diastolic Blood Pressure
- ↑ 1 mmHg per decade
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Pulmonary Congestion
• Induced by blood remaining in the left ventricle after contraction.
• Inhibits blood flow from the lungs & raises bloodpressure in the lung capillaries which forces fluid out of the capillary walls
• This PULMONARY OEDEMA reduces respiratoryfunction and causes individuals to feel out of breathmore quickly.
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Coronary Artery Disease
• The older heart requires more oxygen to pump the same amount of blood around the body as a youngheart.
• This is not important as long as the coronary arteriesremain normal.
• However, age changes cause deficiencies in the normal functioning of coronary arteries.
• ATHEROSCLEROSIS prevents adequate bloodsupply to the heart.
• This causes MYOCARDIAL INFARCTION
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Coronary Arteries
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Age Changes in Arteries
• Loss of elasticity- accumulation of calcium & lipids- breakage of elastic fibres
This loss of elasticity means that vessels are less able to be stretched by blood flow.
- ↑ systolic blood pressure
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• Widening & Lengthening
At first this compensates for elasticity loss but fibres are eventually stretched until they stretch no more.
Each heart contraction causes a rapid and dramatic rise in systolic BP
This leads to increases in cardiac O2 demand
• Diminished Elastic Recoil
Causes slowing of blood flow through arteries
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ATHEROSCLEROSIS
• Most common form of arterial disease forming oneof a group of arterial diseases known as ARTERIOSCLEROSIS.
• Causes the formation and enlargement of scar likematerial called PLAQUE in the walls of arteries.
• Plaque cases arteries to narrow and thus reduces blood flow.
• It also causes stiffening of the arteries reducing theirability to dilate when oxygen demands in crease.
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Age Changes in Arteries
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• Atherosclerosis also involves roughening of the inner lining of arteries and exposure of underlying collagen.
• Both of these factors promote the formation of clotswhich can impede and totally block blood flow.
• Atherosclerosis causes:
- heart attacks- strokes- aneurysms- kidney disease- muscle problems in the legs
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Mechanisms Promoting Atherosclerosis
• Endothelial Dysfunction• Free Radicals
- formation of lipid peroxides
• Blood Low Density Lipoproteins (LDLs)- eg cholesterol & triglycerides
• Elastase- an enzyme that breaks down elastic fibres
• Glycation- the use of glucose to form cross links
between protein molecules
- produces age-related glycation end products(AGEs) and FRs
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Risk Factors in Atherosclerosis
Smoking↑Blood pressureHigh blood LDLsDiabetes MellitusFamily historyAdvancing age
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Age Changes in Capillaries
• Become narrower and irregular in shape
• Decrease in number
• Walls become thicker
• Decreased permeability
• Reduce the ability of the circulatory system toadjust quickly to changes in the demands of the body
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Age Changes in Veins
• Thickening of the walls and valves
• Varicose veins
- ↑ vein diameter
- promotes clot formation
thrombus → embolus
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2. The Respiratory System
Main functions for homeostasis:
• Gaseous exchange
- obtaining 02 & eliminating CO2
Ventilation (breathing)
Perfusion (pulmonary circulation)
Diffusion (02 in & CO2 out)
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Age Changes Affecting Ventilation
• Narrowing of Bronchioles
• Decreased alveolar surface area
• Respiratory muscles become weaker
• Decrease in lung elasticity
Consequences:
↓Rate at which air can circulate through the system
Ventilation is made more difficult and this ↓ 02 supplyand ↑CO2 in the blood.
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Ventilation
Minute Volume = Vol. Per breath x breaths per minute
Vital Capacity = Tidal Volume + Inspiratory Reserve Vol + Expiratory Reserve Vol.
VC = TV + IRV + ERV
Total Lung Capacity = TV + IRV + ERV + Residual Vol. (TLC) (RV)
6.0 litres
2.72.2
1.2
0
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• Ageing does not affect the TLC but does affect thevolumes of air that can be moved.
• The loss in elasticity of the lungs leads to
↓ IRV & ERV
• Tidal volume increases and there are increases inresidual volume
• The vital capacity of the lungs decreases
• These volume changes have two effects:
1) decrease in maximum minute volume.
2) ↓ VC with ↑RV means less fresh air is inspired. This ↓ rate of diffusion.
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Diseases of the Respiratory System
• Respiratory diseases (excluding lung cancer) arethe fourth leading cause of death in the elderly.
• Lung cancer
• Chronic Bronchitis- inflammation of the bronchioles- ↑ mucous production
↓ ventilation by making airways narrower
• Emphysema- destruction of parts of the the lungs
e.g. bronchioles & alveoli
• Pneumonia- inflammation of the lungs → infection
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3. Musculo-Skeletal System
Main functions in homeostasis:
- movement - support- heat production- protection- mineral storage- blood cell production
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Age changes in muscles
• ↓ nerve-muscle interactions
• ↓ muscle mass
• ↓ blood flow in muscles
Consequences
• ↑ Reaction Times (RTs)
• ↓ speed of movement
• ↓ endurance
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Skeletal Age Changes
• Loss of bone matrix(more extensive in post menopausal females)OSTEOPOROSIS
• Stiffening of hyaline Cartilage between joints due to loss of H2O and Ca2+ deposition.OSTEOARTHRITIS
Consequences
• Generalised weakening of the bone(falls tend to cause more fractures in elderly)
• ↓ joint mobility
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4. Nervous System
Main functions for homeostasis:
• monitoring
• communication
• stimulation
• memory
• information processing
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Age Changes in the Nervous System
• Loss of brain volume
• ↓ neurotransmitters, slower
nerve conduction rate.
• ↓ numbers & changes in the
structure of synapses
• ↓ numbers of motor neurons
• slower reflexes
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• memory loss
- ↓ short term memory (STM)
- greatest decline in STM is for information
presented verbally and quickly.
- long term memory is largely unaffected
• increase reaction time ( ↑accidents?)
• vocabulary & conversation
• sleep pattern changes.
• personality changes?
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Diseases of the Nervous System
Cerebro-Vascular Accidents (CVAs) or Strokes
• third leading cause of death in the over 65 age
group
• occur when blood supply to the brain is disrupted
- common result of atherosclerosis
- hypertensive haemorrhagic stokes
• Effects depend upon the site of blockage/leakagein the brain:
- paralysis/paresis- loss of language skills- visual field defects
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Dementias
A broad category of diseases which involve a serious decline in memory and a decline in at least one other major function.
- sufferers cannot carry out normal activities- difficulties must be experienced on a long term
basis- caused by an identifiable physical abnormality
• Number and rate of dementia cases are ↑
• Incidence rate rises exponentially with age
• Effects: ↓ STM, loss of motor function, personality changes
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Alzheimer’s Disease (AD)
• Fifth leading cause of death in the US
• AD is becoming a more important factor of ageingas risks of heart disease & cancer decline
• Early onset or familial ADLate onset or senile dementia of the Alzheimer type
• Causes:Genetic abnormalities?Normal part of the ageing process ?
• Changes in the brain:senile plaques → beta amyloidneurofibrillar tangles → dead neuronslow levels of acetylcholine