C28 - Effects of Ageing on the Nervous System Flashcards
What is Alzheimer’s disease?
AD is a degenerative disease of the nervous system, which particularly affects the temporal and frontal lobes of the brain.
What are the causes of Alzheimer’s disease?
- Increasing age
- Family history of the condition
- Familial AD, when some alleles of a particular gene are inherited. (Very rare)
- Genetic differences e.g. some variants of the apolipoprotein E gene (ApoE) May act as risk factors
- Severe or repeated head injury
- Stroke
- Low level of education and intellectual activity
What’s vascular dementia?
Dementia which occurs due to factors associated with cardiovascular disease.
E.g. high blood pressure, high blood cholesterol and smoking.
Other symptoms of Alzheimer’s disease (AD) are not usually present.
How can the symptoms of AD be divided (into 3 stages)?
Early stages (mild)
Mid-stage (moderate)
Late-stage (severe)
What happens in/are the symptoms in the early stages of Alzheimer’s disease (AD)?
(Mild)
The person can continue to function independently, since memory loss and cognitive deficits are compensated for by the person.
They may start to forget family members’ names, places, objects, and events and find it difficult to express what they want to say.
They may repeat themselves, have reduced ability to make decisions and show poor judgement.
They may also show early signs of mood changes.
What happens in/are the symptoms in the mid-stages of Alzheimer’s disease (AD)?
(Moderate)
Personality changes and physical problems develop and cognitive ability continues to decline.
Person becomes more dependent on others for care and support for daily activities.
Most are unaware they’re forgetting things and can’t communicate coherently.
They’ll show increasing confusion, disorientation, obsessive/impulsive behaviour, disturbed sleep and mood swings.
Poorer judgment of distance.
What happens in/are the symptoms in the late stages of Alzheimer’s disease (AD)?
(Severe)
Loss of control of bodily functions (e.g. urinary and bowel incontinence).
More frequent confusion and disorientation and big personality change.
Language severely affected and can be completely lost.
May become violent and suspicious of people.
Dysphagia (may lose ability to swallow).
What proteins cause the formation of tangles in the brain, causing Alzheimer’s disease?
Tau proteins
What proteins cause the formation of plaques in the brain, causing Alzheimer’s disease?
Beta amyloid proteins
What 2 proteins cause the destruction of brain cells in AD?
Tau proteins (in neurones) and beta amyloid (in myelin sheath surrounding neurones).
What causes Alzheimer’s disease (pathologically)?
Tau proteins exist in neurones and stabilise microtubules.
When Tau proteins become defective, it results in the death of the neurone.
Neurofibrillary tangles form - twisted aggregates of Tau protein that have become hyper-phosphorylated and build up inside the neurones.
When this occurs, the microtubules disintegrate, causing the neurone transport system to collapse (resulting in biochemical communication malfunction).
Proteins are also found in the myelin sheath around neurones. Abnormal breakdown of these proteins produces beta amyloid proteins. These accumulate and form plaques around the axon and dendrites.
How does a healthy brain compare to a brain with Alzheimer’s disease?
A brain with Alzheimer’s is:
- smaller
- more deeply folded
- has plaques and tangles
What are the (3) theories for the molecular causes of AD?
Herpes simplex virus type 1 (may have an affect in people with the ApoE gene)
Age related myelin breakdown in the brain. Iron released during myelin breakdown is thought to cause further damage.
Inflammatory processes associated with aging. E.g. formation of toxic proteins on brain neurone surfaces is thought to be a beta amyloid derivative.
What’s presbycusis?
A progressive disorder, resulting in significant hearing problems with increased age.
What causes age-related hearing loss?
When sensitive hair cells inside the cochlea (inner ear) die and the neurones in the auditory nerve gradually become damaged or die.
What is ARMD?
Age related macular degeneration
A medical condition that usually affects older adults.
It can result in loss of vision in the macula due to damage to the retina.
It’s a major cause of blindness and visual impairment.
(There are 2 types: dry and wet)
What’s dry ARMD (age-related macular degeneration)?
Loss of vision in the macula due to damage to the retina.
This occurs when cellular debris (called drusen) accumulates between the retina and choroid, causing the retina to become detached.
(Most common form of ARMD)
What’s wet ARMD (age-related macular degeneration)?
Loss of vision in the macula due to damage to the retina.
This is more severe than dry ARMD, as blood vessels grow up from behind the retina.
The blood vessels can leak blood and fluid into the retina, which can cause scarring and damage to the macula, resulting in visual distortion and blind spots.
The retina can also become detached.
(It can be treated with laser coagulation and medication can prevent growth of blood vessels).
What’s a cataract?
The clouding of the lens in the eye which leads to a decrease in vision.
What are the 3 main types of cataract?
Nuclear
Cortical
Subcapsular
What are nuclear cataracts?
A type of cataract which makes it difficult to recognise the intensity of colours (but reading vision won’t normally change).
What are cortical cataracts?
A type of cataract which can cause problems with glare when driving.
There may also be difficulty in reading and low sun in winter causes discomfort as it shines into the eyes.
What are subcapsular cataracts?
A type of cataract which can make vision poor during the daytime, making it difficult for a person to drive and have more problems reading.
What factors increase the risk of cataracts?
Ageing
Diabetes
Smoking
Regularly drinking excessive amounts of alcohol
Lifelong exposure of the eyes to UV sunlight
Long term or high dose use of corticosteroid
Previous eye surgery or injury
Family history of cataracts
