Postural control and gait

Question 1

Postural control

Answer 1

-needs to be maintained at rest and during locomotion

Question 2

Postural muscles

Answer 2

-extensor muscles of the limbs
-axial muscles of vertebral column

Question 3

Postural muscle control

Answer 3

-Cortical UMN synapse on brainstem UMNs which then synapse on LMNs of the axial muscles of vertebra and extensor muscles of limbs
-control/modulation from cerebellum

Question 4

Vestibular nucleus and reticular nuclei postural control

Answer 4

-these nuclei tend to be excitatory to extensor muscles and inhibitory to flexor muscles
*Overall activation of extensor muscles

Question 5

Red nucleus (midbrain) postural control

Answer 5

-excitatory to the flexors and inhibitory to extensors

Question 6

Cortical UMNs postural control

Answer 6

-tend to inhibit activity of the vestibular and the reticular nuclei
*Decreases extensor tone

Question 7

Cerebellum postural control

Answer 7

-provides strong inhibition to the vestibular nucleus
-BUT it can excite or inhibit UMNs in cortex or brainstem

Question 8

Lesions to postural centers

Answer 8

1.Forebrain lesion
2. midbrain lesion
3. Cerebellum

Question 9

Forebrain lesion to postural control

Answer 9

-damage to UMN in cerebral cortex
-loss of inhibition to vestibular and reticular nuclei
**RESULT: extensor rigidity = Opisthotonus (severe)

Question 10

Midbrain lesion to postural control

Answer 10

-extensor rigidity that does not normalize

Question 11

Cerebellum to postural control

Answer 11

-disinhibition of vestibular nuclei
-RESULT: extensor rigidity= opisthotonos (when severe)

Question 12

Coordination of locomotion

Answer 12

-in domestic species, requires all 4 functional limbs to be intricately connected

Question 13

What levels does the coordination of locomotion occur?

Answer 13

-cerebrum (cerebral cortex and subcortical structures)
-brainstem
-cerebellum
-spinal cord

Question 14

Locomotion modification and maintenance

Answer 14

-conducted in real time via:
>proprioceptive feedback (cerebellum and cerebral cortex)
>conscious inputs to locomotor structures (ex. does the animal still want/need to be moving)
>information from forebrain, midbrain, cerebellum

Question 15

Inter-limb coordination

Answer 15

-left-right coordination
-forelimb-hindlimb coordination

Question 16

Central pattern generators (CPGs)

Answer 16

-neuronal circuits located diffusely throughout the spinal cord. They are responsible for the rhythmicity of limb movements
>can function in the absence of sensory or descending motor input
>pathways connect limbs from opposite sides of the body and the opposite girdles but also allow limbs to have individual locomotion (eg. Digging)

Question 17

Border cells

Answer 17

-located at the edge (border) of the ventral grey matter throughout the lumbar spinal cord (L1-L7) which plays a role in forelimb-hindlimb coordination
>Pelvic limbs send inhibitory signal to forelimbs but when this is broken, will result in stiff excitatory limbs. Stiff hind limbs, no voluntary movement. Decreased proprioceptive.
**When damaged, results in Schiff-Sherrington phenomenon (very severe lesion). After a few hours, will resolve itself!