Neurology 2 Flashcards
What do lower motor nuerones command?
Muscle contraction
What neurones does the LMNs comprise of?
Alpha motor neurones - generate force
Gamma motor neurones - innervate sensory muscle spindle
Where do axons of the LMNs exit the spinal cord?
`In ventral roots (or via cranial nerves)
Each ventral root joints with a dorsal root to form what?
Mixed spinal nerve
What is the collection of alpha motor neurones that innervate a single muscle termed?
Motor neurone pool
Force of muscle contraction is graded by alpha motor nuerones by 2 principles - what are they?
- Frequency of action potential discharge
2. Recruitment of additional, synergistic motor units
What can be said about the positioning of LMN innervating axial muscles compared to distal muscles?`
Axial are more medial
What can be said about the positioning of LMN innervating flexors compared to extensors?
Flexors are dorsal
What are the three sources of input to an alpha motor neurone that regulate its activity?
- Central terminals of dorsal root ganglion cells whose axons innervate muscle spindles
- UMNs in motor cortex and brain stem
- Spinal interneurones
What do fast and slow muscle fibre types differ in?
How fast myosin ATPase splits ATP to probide energy
How is ATP derived in type I fibres?
Oxidative phosphorylation
How is ATP derived in type IIb fibres?
Glycolysis
In fast type muscle what size are the alpha motor neurones?
`Big
What motor neurone innervates intrafusal fibres in spindles?
Gamma motor neruone
What spinal level is assessed in supinator wrist?
C5-C6
What spinal level is assessed in Biceps?
C5-C6
What spinal level is assessed in triceps
C7
What spinal level is assessed in quadriceps
L3-L4
What spinal level is assessed in gastrocnemius (ankle)
S1
In what activities are static gamma motor neurones active?
When muscle length changes slowly and predictably
In what activitres are dynamic gamma motor neurones active?
Muscle length changes rapidly and unpredictably
What are golgi tendon organs in series with?
Extrafusal fibres
What are golgi tendon organs innervated by>?
Group Ib sensory afferents
What do golgi tendon orgabns do?
Act to regulate muscle tension to protect them from overload
What is the role of spinal interneurones?
Limb movement control of flexors and extensors
What mediates the inverse stretch reflex and reciprocal inhibition between extensor and flexor muscles?
Inhibitory interneurones
What do excitatory interneurones mediate?
The flexor reflex
The crossed extensor reflex
What reflex enhances postural support during withdrawel of foot from painful stimulus?
Crossed extensor reflex
What structures control strategy in motor control?
Neocrotical association areas basal ganglia
What structures conrol tactics in motor control?
Motor cortex
cerebellum
What strucutres control execution in motor control?
Brain stem
Spinal cord
Where do descending spinal tracts originate from?
Cerebral cortex and brain stem
What controls lateral pathways which are important for voluntary control of distal musculature (hands and fingers)?
Cerebral cortex
What controls ventromedial pathways which are important for control of posture and locomotion?
Brainstem
What is the major lateral pathway?
Corticospinal or pyramidal tract (longest tract)
In the corticospinal or pyrimidal tract where do most fibres decussate?
At the pyramidal decussation to form lateral corticospinal tract (from medullary pyramid_