Motorneuornes, Weakness, Paralysis

Question 1

Upper motor neurones

Answer 1

Cell bodies in primary motor cortex of the brain, synapse onto lower motor neurones or on interneuones in the spinal cord (or in brainstem motor nuclei)

Question 2

Lower motor neurones

Answer 2

Cell bodies into grey matter of spinal cord (or in brain stem motor nuclei) axons in travel in peripheral nerves and synapse onto

Question 3

What is looked for in a clinical motor assessment

Answer 3

-co ordination, balance, perception
-observation
-muscle power
-muscle tone
-deep superficial reflexes
-eyes
-mouth
-facial expression

Question 4

What determines the strength of muscle contraction

Answer 4

1)number of active motor units in a muscle- recruitment
More motor unit (lower motor unit, connected muscle tissue) recruited = more muscle strength
2)frequency of action potentials is received by muscle fibres in active motor units> firing units

Question 5

Monoaminergic input

Answer 5

Arousal activity from brain stem onto LMN circuits- if you are excited, you can work harder

Question 6

Spinal reflexes

Answer 6

-knee jerk reaction (but can be activated from any accessible tendon)
-simple, fast, spinal, monosynaptic, reflex
-can be modulated by higher centres
-can be normL, absent, hyper or hypo reacitve

Question 7

Clinical testing of withdraw reflex

Answer 7

-flexor plantar reflex
-sharp instrument stroked on the side of the foot
-big toe flexion> sole of foot curves into stop contact with painful stimulus (normal, negative babinksi)
-big toe extension> abnormal positive babinksi suggests a problem with descending tracts

Question 8

UMN lesions

Answer 8

-sites of damage (axons in descending tracts of the spinal cord, cell bodies in motor cortex)
Clinical findings:
Increased muscle tone
Muscle paralysis or weakness
Hyper reflexive
Positive Babinski

Question 9

LMN lesions

Answer 9

-sites of damage: muscle fibres, nmj, mn axon
Clinical findings:
Muscle wasting
Muscle weakness
Fasiculation
Decreased muscle tone
Decreased reflexes

Question 10

Examples of LMN disease

Answer 10

• motorneurone disease- progressive death of UMN’s and LMN’s
• Infection/ inflammation of nerves- Bell’s palsy
• Accidental section/ compression of peripheral nerves or spinal roots- sciatica
• Failure of NMJ transmission - myasthenia gravis
• Muscle fibre disease-myopathy, muscular dystrophy