Motor Control I

Question 1

Lower motor neurons

Answer 1

-cell bodies in CNS, axons into PNS
-innervates brainstem, cranial nerves (except 1, 2, 8), spinal cord

Question 2

Upper motor neurons

Answer 2

-motor neurons that synapse on other UMNs or LMNs to control movements or functions
-located in cerebrum, midbrain, pons, medulla
-cell body within CNS, axons in CNS

Question 3

Initiation of UMNs

Answer 3

-UMNs are CNS motor neurons with cell bodies in the brain and have axons that travel through the brain and spinal cord to synapse with LMNs in the brainstem and spinal cord
**lesions to UMNs= paresis or paralysis= loss of voluntary control

Question 4

Brainstem UMNs

Answer 4

-midbrain
-pons
-medulla
**most voluntary movement come from the brainstem in domestic species

Question 5

Nuclei of UMNs

Answer 5

**bilateral structures
-Red nucleus
-vestibular nucleus
-reticular nuclei

Question 6

Red nucleus

Answer 6

-lives in midbrain, crosses over immediately and descends down brainstem, out to the spinal cord (dorsal part of lateral funiculus
**Rubrospinal Tracts
-dorsal part of lateral funiculus

Question 7

Red nucleus/rubrospinal tract function

Answer 7

-activate flexor muscles, inhibit extensor muscles

Question 8

Vestibular nucleus

Answer 8

-lives in medulla, go through brainstem and down spinal cord (ventral funiculus)
-no crossing over/stays ipsilateral
**vestibulospinal tracts

Question 9

Vestibular nucleus Function

Answer 9

-excite the extensors, inhibit the flexors

Question 10

Net effect of reticular nuclei

Answer 10

-excite extensor muscles

Question 11

Brainstem UMN activation

Answer 11

-brainstem UMNs are activated by input by motor cortex through cortical UMNs
(pg 16?)

Question 12

Cortical UMNs (motor cortex)

Answer 12

-axons crossover at caudal medulla (just before spinal cord starts) = corticospinal tracts
-does not extend past forelimbs and instead these corticospinal tracts descend and synapse on brainstem nuclei/UMNs in domestic species
**All brainstem nuclei NEED input from motor cortex to have voluntary/conscious movements

Question 13

Control of locomotion

Answer 13

-spinal cord contains circuitry to allow for motor movements
>reflex arcs= patella, withdrawal, cross extensor AND stretch receptors
»allows for stepping and weight support as long as the higher motor cortex and brainstem nuclei and functioning
-central pattern generators- involved in rhythmicity of movement
-border cells- talking between limbs

Question 14

Reticular nuclei

Answer 14

Reticular nuclei
-come from multiple nuclei and go to multiple destinations,
-lateral or ventral funiculus
-sometimes they cross over, sometimes they don’t
**reticulospinal tract