Motor Systems

Question 1

The somatic nervous system is made up of which nerve fibres?

Answer 1

Upper motor neurone
Lower motor neurone
Neuromuscular junction
Skeletal muscle

Question 2

Where are UMNs and LMNs found?

Answer 2

UMN in CNS only

LMN body in CNS, axon in PNS

Question 3

What is the function of a UMN?

Answer 3

Regulation/modification and termination of LMNs

Can be 1:1, many:1 or via inter neurones

Question 4

When a LMN fires without an UMN, what is this called?

Answer 4

Reflex

Question 5

UMNs - LMNs supplying flexor muscles travel in which part of the spinal cord?

Answer 5

Lateral funiculi

Question 6

UMNs - LMNs supplying extensor muscles travel in which part of the spinal cord?

Answer 6

Ventral funiculi

Question 7

Which LMNs supply the forelimb

Answer 7

C6-T2

Question 8

Which LMNs supply the hindlimb?

Answer 8

L4-S3

Question 9

Which muscles, extensor or flexors, are more dominant and whY?

Answer 9

Extensor

Maintain posture against gravity

Question 10

If damaged, LMNs can result in muscle bulk & tone loss, and atrophy. Why is this?

Answer 10

Have constant subthreshold potential

Always slightly contracting

Question 11

What are the differences between small and large motor units?

Answer 11

Small - few muscle fibres per motor neurone, accurate

Large - many muscle fibres per motor neurone, more force but less accurate

Question 12

Spinal nerves are distributed by rami and plexi. What are these?

Answer 12

Branches e.g. rami communicante - autonomic nerve supply to each spinal nerve
Networks

Question 13

Somatic reflexes are innate, not conditioned. Is th brain involved?

Answer 13

No, but should be aware

Check facial expression

Question 14

How does the brain know about a reflex if it is not involved?

Answer 14

Muscle spindle stretch receptors

Question 15

Reflexes can be monosynaptic/polysynpatic, ipsilateral or contralateral, intrasegmental or intersegmental. What do these mean?

Answer 15

1 or many synapse
Same side or opposite side
In one segment or within multiple segments

Question 16

Do somatic reflexes require a UMN?

Answer 16

N

Question 17

What happens when an UMJ is injured?

Answer 17

Normal or increased tone
Atrophy - disuse
Decreased coordination but same strength

Question 18

What happens when a LMN is damaged?

Answer 18

Loss in muscle bulk/tone

Atrophy

Question 19

What are the 5 types of UMN tracts and what does each one do?

Answer 19

Corticospinal - fine motor skills. Includes corticonuclear (cortex to cranial nerve)
Rubrospinal tract - skilled movements
Tectospinal tract - moves head/eyes
Reticulospinal - stabilise body against gravity

Question 20

What is the function of the cerebellum? Can it initiate movement?

Answer 20

Coordinates sensory input from cerebral cortex

No