Chapter 28: The Effect of ageing on the Nervous System Flashcards
Definition of dementia?
Loss of cognitive ability associated with gradual death of brain cells.
What is Alzheimer’s disease
Degenerative disease of the nervous system that particularly affects the temporal and frontal lobes of the brain.
Risk increases with age
Peptide molecule Beta-amyloid are produced by normal cerebral cortex neurones throughout life
An abnormal form of B-amyloid is associated with formation of plaques.
Causes of Alzheimer’s disease
Exact cause is unknown.
Multifactorial disease
- Increasing age - risk doubles every 5 years over age of 65.
- Family history of condition means risk is higher
What is familial AD?
Some alleles are known to cause AD, so inheriting them leads to early onset of disease (30-40)
Autosomal dominant alleles. - caused by:
Mutations in one of 3 genes:
- Gene for amyloid precursor protein (APP)
- gene for presenilin 1 and 2
What is sporadic AD?
Majority of cases are this. Risk factors: - Stroke - Severe or repeated head injury - Low level of education and intellectual activity - Variants of apolipoprotein E gene.... UNFINISHED!!!
What is vascular dementia?
Risk factors
- High BP
- Smoking
- High blood cholesterol
Memory and cognitive impairment occur due to reduced blood flow to the brain.
Often occurs as result of mini-strokes
Other symptoms of AD aren’t present, eg, no plaques
3 Main stages of development of AD
Early stages (mild AD)
Mid-stage (moderate AD)
Late-stage (severe)
Information on the early stages of AD
Memory loss + other cognitive deficits compensated for by the person, so can still function independently.
Difficult to express themselves.
Early signs of mood changes, eg, increased anxiety, agitation, confusion.
Ability to make decisions is reduced, as poor judgement.
Information on the mid-stages of AD
Personality changes and physical problems as cognitive ability declines further.
They require more care and support for daily activities
Increased confusion and disorientation
Disturbed sleep + mood swings
Information on the late-stages of AD
Symptoms more severe - distressing for patient, family, carers.
urinary + bowel incontinence
Completely dependent on care for daily life.
Frequent confusion and disorientation
Dysphagia.
Lifestyle choices to reduce age-related memory?
Regular Exercise Social Interaction Eating plenty of fruits and vegetables and drinks such as green tea. Managing stress Getting sufficient sleep Not smoking.
How does regular exercise help to reduce age-related memory?
Boosts brain growth factors
encourages development of new brain cells
How does social interaction help to reduce age-related memory loss?
Helps brain function by involving activities that challenge the mind.
Helps reduce stress and depression
How does eating plenty of food and vegetables and drinks such as green tea?
Contain abundant antioxidant
Foods rich in omega-3 fats (such as salmon, tuna, walnuts, flaxseed) have been found to improve memory
How does managing stress help to reduce age-related memory loss?
Cortisol, the stress hormone, damages the brain over time and an lead to memory problems
How does getting sufficient sleep help to reduce age-related memory loss?
Sleep is necessary for memory consolidation, the process of forming and storing new memories.
Lack of sleep also reduces growth of new neurones in the hippocampus.
Can cause problems with memory, concentration and decision-making.
How does not smoking help to reduce age-related memory loss?
Increase the risk of vascular disorders
Can cause stroke
Leads to constriction of arteries that deliver oxygen to the brain.
Differences between normal age-related memory changes and symptoms that indicate dementia?
Normal
- Person can live independently and carry out normal activities, despite occasional memory lapse.
Dementia
Person has difficulty performing simple daily tasks (washing up, dressing appropriately)
Normal
Person can recall and describe incidents of their forgetfulness
Dementia
Person unable to remember or describe incidents of their memory loss
Normal
Person’s judgement and decision -making ability is unaffected.
Dementia
Person has trouble making choices and may show poor judgement
Normal
Person may pause to remember directions but doesn’t get lost in familiar locations
Dementia
Person gets lost or disorientated even in familiar locations.
Examples of normal memory lapses?
- Forgetting where regularly used items have been left, eg, glasses/keys
- Forgetting names of acquaintances or blocking one memory with a similar one, eg, calling grandson by son’s name.
- Occasionally forgetting an appointment
- Having trouble remembering what the person has just read.
- Becoming easily distracted
- Walking into a room and forgetting why they went there.
Main difference between age-related memory loss and dementia?
Age-related memory loss isn’t disabling.
When memory loss becomes severe - disrupts person’s work, hobbies, social activities, family relationships. - possible warning signs of Alzheimer’s disease.
Causes of hearing impairments
Sensitive hair cells in cochlea (inner ear) damaged and die
Neurones in auditory nerve become damaged and die.
Other causes of hearing loss?
Noise-induced hearing loss caused by long-term exposure to sounds that are too loud, or for too long - damage sensory hair cells - once hair cells are damaged they don’t grow back and ability to hear is diminished
High blood pressure or diabetes
medications that are toxic to sensory cells in ears, eg, some chemotherapy drugs.
Disorders that affect vision as we age?
Age-related macular degeneration (ARMD)
Cataracts
Glaucoma
What is ARMD?
Age related macular degeneration
Can result in loss of vision in centre of visual field ( the macula) due to damage to the retina.
Two types - Dry ARMD, wet ARMD
What is dry ARMD
Most common form - 90%
Cellular debris (called drusen) accumulates between retina and choroid.
Causes retina to become detached.
Vision lost slowly over a period of years.
may go on to develop wet ARMD
What is wet ARMD
More severe form.
Blood vessels grow up from choroid behind retina and leak blood and fluid into retina (sub retinal haemorrhage)
This causes scarring and damage to macula
Results in visual distortion and blind spots.
retina can become detached
Effect of ARMD on lifestyle?
Make it difficult or impossible to read or recognise faces
Enough peripheral vision usually remains to allow other activities of daily life.
Usually affects both eyes, but peripheral vision means not complete blindness.
What are cataracts?
Main cause of impaired vision worldwide
Some age-related cataracts.
May be partial or complete, stationary or progressive, hard or soft.
Immature cataracts have some transparent protein
Mature cataracts have fully opaque lens.
3 Main types of cataracts
Nuclear cataracts
Cortical cataracts
Subcapsular cataracts
Info on Nuclear cataracts
Makes it difficult to recognise intensity of colours
Reading vision normally unaffected.
Info on cortical cataracts
May cause problems with glare when
driving
May be a difficulty in reading
May find sunlight uncomfortable during winter because of sun being lower on horizon and shining into eyes.
Info on sub capsular cataracts
Can make vision poor during daytime
Makes its difficult for person to drive
Problems reading
Causes of cataracts
Exact cause of age-related cataracts not fully known
May be result of changes in structure of lens over time
Cloudy area in lens may be result of changes in proteins that make up lens.
Other risk factors for cataracts
Diabetes Smoking Regularly drinking excessive volumes of alcohol. Poor diet lacking in vitamins Lifelong exposure of eyes to UV sunlight
Treating age-related cataracts
Treated using stronger glasses + brighter reading lights for period of time,
As cataracts worsen - surgery
Surgery involves removing cloudy lens through small incision in eye and replacing with clear plastic lens. Only recommended if loss of vision has significant effect on daily lifestyle. Local anaesthetic needed.
What is glaucoma?
Group of eye conditions that affect vision, caused by increased intraocular pressure due to build up of aqueous humour that can’t drain. This leads to optic never damage. Can lead to permanent blindness if left untreated.
4 main types of glaucoma?
Chronic open-angle glaucoma
Primary angle-closure glaucoma/acute glaucoma
Secondary glaucoma
Developmental glaucoma/ congenital glaucoma
Info on chronic open-angle glaucoma?
Most common type
Develops slowly
Caused by blockage of drainage channels
Prevents aqueous humour draining away.
causing increase in intraocular pressure.
Left untreated- tunnel vision - blindness.
Treated by eye drops (reduce volume of fluid produced by eye), laser eye surgery
Info on primary angle-closure glaucoma/acute glaucoma?
Rare form
Can be chronic/acute
Sudden painful build-up of pressure in eye.
Edge of iris and cornea come into contact with each other - pressure rises suddenly as aqueous fluid can’t reach drainage channels between them
eye becomes red + painful - severe headaches, blurred vision, nausea, vomiting,
Needs immediate treatment to reduce pressure. - laser eye surgery.
Info on secondary glaucoma?
Result of eye injury or eye condition, eg, uveitis (inflammations of iris or inflammation of iris and ciliary body)
Info on developmental glaucoma/congenital glaucoma?
Can be very serious
Usually present at birth or develops shortly after birth.
Treatment for glaucoma?
Eye drops, laser treatment or surgery.
Early diagnosis essential to avoid permanent damage to eyes.
Effect cannot be reversed
How would an audiologist carry out a hearing test?
Put headphones over patient’s ears
Select frequency of noise and play sound in one ear.
Increase decibel level until person detects sound.
Repeat over range of frequencies, and repeat with other ear.
Display results on audiogram.
Two possible social consequences of hearing loss for an elderly person?
Isolation, frustration, embarrassment and anger as misunderstanding what’s being said.
Decreased social interactions.
What is a hearing impairment?
Age related hearing loss = presbycusis
Progressive disorder
High pitched sounds become more difficult to detect as person ages.
Preventing and treating AD?
Can’t prevent or treat
Can only reduce symptoms.
Drugs inhibit acetylcholinesterase can slow down rate of decline or Ach.
NOT FINISHED!!!!
What causes the destruction of brain cells and pathology of AD?
Caused by presence of Tau protein tangles.
Tau proteins stabilise microtubules and are abundant in neurones of CNS. When Tau proteins become defective, neurone death occurs.
Neurofibrillary tangles are twisted aggregates of Tau proteins that have become hyper-phosphorylated, and build up inside neurones. When this occurs, microtubules disintegrate, causing neurone’s transport system to collapse, which causes biochemical communication between neurones to malfunction, and results in neuronal death.
Proteins are found in myelin sheath around neurones. Abnormal breakdown of these proteins produce B amyloid proteins that accumulate and form plaques outside and around axons and dendrites. Neurones then have shorter and fewer neural connections - loss of neurones.
Symptoms of AD.
Initially, when disease starts to destroy brain cells, no outward symptoms.
Progressive memory loss
Abnormal cerebral cortex
Formation of plaques
Shrivelled and fewer brain cells
Shorter and fewer dendrites
Cells in region of plaques and tangles secrete less neurotransmitter acetylcholine.
People usually live ~8-10years after symptoms appear.
AD not usually cause of death - malnourishment + pneumonia, as can’t communicate they are unwell.
What are plaques?
Deposits of abnormal B amyloid between neurones.
How is the biochemical communication between neurones disrupted?
- Nerve impulses fail to reach end of presynaptic neurone
- Calcium channels fail to open
- Less Ach made.
- vesicles can’t fuse with presynaptic membrane - no exocytosis
- Ach not broken down in synaptic cleft due to deficiency of choline acetyltransferase activity.
MRI and PET scans info?
Show reduction in size of specific brain regions as condition develops from mild-cognitive impairment to AD.
Molecular causes of AD?
- Herpes simplex virus type 1 with people carrying versions of the poE gene.
- Age-related myelin breakdown in brain which released iron.
- Inflammatory processes associated with ageing
eg, formation of toxic proteins on surface of brain neurones due to B-amyloid-derived diffusible ligands (ADDLS)
ADDLS only affect neurones involved in AD by binding to cell surface receptor on neurones and changing shape of synapse - disrupts nerve impulse transmission.
Treatment of wet ARMD?
Can be treated with laser coagulation.
medication can stop and sometimes reverse growth of blood vessels.
