Motor Systems Flashcards
The somatic nervous system is made up of which nerve fibres?
Upper motor neurone
Lower motor neurone
Neuromuscular junction
Skeletal muscle
Where are UMNs and LMNs found?
UMN in CNS only
LMN body in CNS, axon in PNS
What is the function of a UMN?
Regulation/modification and termination of LMNs
Can be 1:1, many:1 or via inter neurones
When a LMN fires without an UMN, what is this called?
Reflex
UMNs - LMNs supplying flexor muscles travel in which part of the spinal cord?
Lateral funiculi
UMNs - LMNs supplying extensor muscles travel in which part of the spinal cord?
Ventral funiculi
Which LMNs supply the forelimb
C6-T2
Which LMNs supply the hindlimb?
L4-S3
Which muscles, extensor or flexors, are more dominant and whY?
Extensor
Maintain posture against gravity
If damaged, LMNs can result in muscle bulk & tone loss, and atrophy. Why is this?
Have constant subthreshold potential
Always slightly contracting
What are the differences between small and large motor units?
Small - few muscle fibres per motor neurone, accurate
Large - many muscle fibres per motor neurone, more force but less accurate
Spinal nerves are distributed by rami and plexi. What are these?
Branches e.g. rami communicante - autonomic nerve supply to each spinal nerve
Networks
Somatic reflexes are innate, not conditioned. Is th brain involved?
No, but should be aware
Check facial expression
How does the brain know about a reflex if it is not involved?
Muscle spindle stretch receptors
Reflexes can be monosynaptic/polysynpatic, ipsilateral or contralateral, intrasegmental or intersegmental. What do these mean?
1 or many synapse
Same side or opposite side
In one segment or within multiple segments
Do somatic reflexes require a UMN?
N
What happens when an UMJ is injured?
Normal or increased tone
Atrophy - disuse
Decreased coordination but same strength
What happens when a LMN is damaged?
Loss in muscle bulk/tone
Atrophy
What are the 5 types of UMN tracts and what does each one do?
Corticospinal - fine motor skills. Includes corticonuclear (cortex to cranial nerve)
Rubrospinal tract - skilled movements
Tectospinal tract - moves head/eyes
Reticulospinal - stabilise body against gravity
What is the function of the cerebellum? Can it initiate movement?
Coordinates sensory input from cerebral cortex
No
