Nervous system: The motor system Flashcards
What is the effect of upper motor neurones on lower motor neurones?
They have a net inhibitory effect
What are the signs of lower motor neurone damage?
- weakness
- muscle wasting (LMN provides growth factors)
- Areflexia or hyporeflexia
- Fasciculation (ectopic Ach receptors)
- Fibrillation
What are the signs of upper motor neurone damage?
- weakness
- Hypertonia
- Hyper-reflexia (loss of inhibition)
- Primitive reflexes return
What is the appearance of spasticity in an UMN lesion?
The upper limb is flexed and the lower limb is extended - this is due to the strongest agonistic muscle dominating eg bicep stronger than tricep so arm flexes
Name different types of rigidity
- lead pipe
- clasp knife
- cogwheel
What causes lead pipe rigidity?
Parkinsons
What causes cogwheel rigidity?
Parkinsons
What causes clasp knife rigidity?
Spasticity caused by upper motor neurone lesions
What is the pathophysiology of parkinsons?
Degeneration of the substantia nigra which causes dopamine deficiency
What is the classical triad of symptoms seen in parkinsons?
Bradykinesia, tremor (pill-rolling and at rest) and rigidity (cogwheel)
What are some associated features of parkinsons?
- Lewy body dementia
- Smaller handwriting
- Quiet voice
- Mask-like facial expression
- Anxiety and depression
- Shuffling gait
What is the pathophsiology of huntingtons disease?
An autosomal dominant progressive disorder caused by cell loss in the basal ganglia and cortex
What is the age of onset of huntingtons?
30-50 years
Life expectancy is ~20 years after symptoms develop
What are the symptoms of huntingtons?
- Chorea (abnormal unintentional movements)
- incoordination
- dystonia (abnormal tone)
- cognitive decline
- behavioural difficulties
What is the primary treatment for parkinsons? What are the associated side effects?
L-DOPA which is converted into dopamine via AADC - aromatic amino acid decarboxylase.
Excess dopamine in the periphery causes GI side effects such as nausea, anorexia
