Nervous System 2

An introduction to nuclei...

Nuclei of the basal ganglia:

• Substantia nigra
• Caudate
• Putamen
• Globus pallidus

These nuclei are associated with allowed us to develop highly skilled behaviour.

Basal ganglia disease: increase or decrease in the motor output of the cortex

Parkinson's Disease

Cause: unknown, damage to nigral neurons

Characteristics: extrapyramidal, progressive movement disorder, chronic degenerative disorder

Symptoms: tremor, jerky movements, rigidity, mask-like face, stiff heavy and tired limbs, lead-pipe resistance

Akinesia

Definition: loss of associated and voluntary movements of all skeletal muscles

Symptoms: inability to maintain upright position, saliva dripping, gait step, dementia, depression

Huntington's Disease

Age group: 30-50 years

Cause: degeneration of caudate, putamen and front cerebral cortex due to autosomal dominant trait

Characteristics: enlarged lateral ventricle, decrease in Ach and GABA, increase in dopamine

Treatment: no treatment

Death: 10-20 years after symptoms onset

Dementia

Site: cerebrum

Types: alzheimer's disease, vascular dementia, lewy body dementia, fronto-temporal dementia, alcohol/drug related dementia, Huntington's dementia, Parkinson's dementia, AIDS related dementia

Alzheimer's Disease (dementia)

Cause: genetic factors

Site: cerebral cortical degeneration of frontal, temporal and parietal lobes

Characteristics: atrophy of brain (frontal lobe especially) with enlarged ventricular system, decreased Ach in the brain, narrowed gyri and wide sulci

Risks: vascular diseases, low mental and physical activity, nutrition deficiency, drug/alcohol abuse, mutationin genes, Down's syndrome, age and stress

Pathogenesis of alzheimer's disease is outlined below:

1. The amyloid precursor gene is mutated
2. The mutated gene produces abnormal amyloid protein, which is longer, stickier and less soluble. The mutated gene has a difficult protein pattern.
3. Aß is the main component of plaque and tau protein
• Plaque: Aß proteins accumulate to form clumps called neuritic plaques, which aggregate and form amyloid plaques. They are spherical lesions in the cerebral cortex.
• Tau protein: long, sticky, foldable proteins twisted around one another in neuronal cells that interfere function by displacing neuronal organelles. Nerve impulses cannot travel, affecting the exchange of messages at the synaptic cleft with the next neuronal dendrites.
4. Aß is deposited, which is specific for alzheimer's
5. Aß is toxic to brain cells and small quantities can destroy brain cells
6. Damage to the hippocampus of the brain explains the impairment of memory and involvement of the association cortex correlates with the loss of higher intellectual functions

There are three stages of alzheimer's, which are:

     1. Early Stage

• Loss of memory (hippocampus)
• Disorientation of time and date (parietal lobe)
• Language difficulties (language areas)
• Personality changes (frontal lobe)

     2. Intermediate Stage

• Continuous memory loss
• Diminished problem solving skills
• Motor effects
• Impaired judgment
• Inappropriate social behaviour
• Lack of insight and abstract thinking

     3. Late Stage

• Continuous memory loss and mental function
• Unable to recognise family and friends
• Apathy (lack of concern or interest)
• Severe deterioration of speech
• Dehydration
• Depression
• Pneumonia

Multiple Sclerosis

Characteristics: the myelinated neurons of the CNS degenerate due to an autoimmune disease, multiple antibodies attack myelin neurons on numerous occasions, causing inflammation and destructive lesions

Cause: potentially due to a virus

Age group: 20-40 (Caucasians, female)

Site: optic nerve, brain stem, cerebellum, corticospinal tract and spinal nerves

The types of multiple sclerosis are summarised below:

1. Relapsing-Remitting: most common, series of attacks that completely or partially disappear afterwards until another attack occurs (pregnancy reduces no. of attacks)
2. Primary-Progressive: 10-20% of MS, continuous gradual decline in physical abilities
3. Secondary-Progressive: second stage of relapsing-remitting
4. Progressive Relapsing: steady decline since onset of superimposed attacks

Symptoms: lesions, mild to severe episodes, visual disturbances, muscle numbness and weakness, coordination and balance disturbances, loss of sensation, speech impediment, dementia