motor system Flashcards
what tracts are found in the motor system
pyramidal tracts
what are the two pyramidal tracts
cortiospinal
corticobalbur
where does the corticobalbur decusate
at the level of the pons for cranial nerve 7
where does the corticospinal decusate
at the medulla (lateral)
the medial/anterior one is ipsilateral
what anatomical function does the anterior horn cell perform
used to distinguish UMN and LMN
what are the features of a UMN lesion
weakness
* extensors in arms weaker than flexors
* flexors in legs weaker than extensors
increased tone (spastic)
increased tendon reflex
extensor plantar response = babinski sign
clonus
what are the features of a LMN lesion
- weakness
- wasting
- reduced tendon reflex
- reduced tone
- fasciculations may be present (brief spontaneous contraction)
what results from cervical lesions
mixed UMN and LMN presentation
UMN signs below the lesion
LMN signs at the level of the lesion
how does atrophy occur in LMN
loss of LMN input at the neuromuscular junction results in breakdown of actin and myosin resulting in decreased muscle size
how does atrophy occur in UMN
this can occur due to decreased muscle utilisation but the magnitude and rate of progression is much less pronounced as the LMN lesion
what causes arm drifts
UMN weakness and this is due to muscle weakness as you cant maintain the contractions
what is isometrexia
difficulty in maintaining a contraction of a muscle. cannot hold object for too long
what is tone
contraction of a muscles at rest or during passive movement
power grading
5 = normal
4 = good but weaker than normal)
3= fair ( can move joint or muscle againts gravity)
2= poor (patient can move joint if gravity is removed) - horizontal plane
1= trace ( can contact muscle but no joint movement)
0 = zero (complete paralysis)
what type of reflex is the tendon reflex
monosynaptic proprioceptive reflex
