23 – Motor Control II

Question 1

SC contains circuitry that allows for motor movements:

Answer 1

-stepping + weight support
-stretch receptors + reflex arcs=central pattern generators (coordinate movements between L+R and fore+hind)

Question 2

Brainstem control of locomotion:

Answer 2

-initiation of locomotion
-maintain balance (ex. vestibular nuclei) and posture
-coordination of gait

Question 3

Cerebral cortex control of locomotion:

Answer 3

-voluntary movements
-visually guided movements
-navigate uneven terrain, obstacles or any voluntary adjustments
**UMNs of cortex control activity of brainstem nuclei

Question 4

Memory of stepping over objects can be stored in:

Answer 4

-parietal lobe (short-term memory)
*most domestic animals can’t really see their hindlimbs so when they see an object they ‘remember’ that their hindlimbs need to step over it
Ex. stopping them part way and removing object=will still ‘hop’ to get over it

Question 5

3 levels of control of locomotion:

Answer 5

-spinal cord (LMN)
-brainstem (UMN from nuclei)
-cerebral cortex (UMN influencing brainstem)

Question 6

Cerebral cortex involvement on SC in domestic species:

Answer 6

-limited=can’t control movement of limbs
>ends at C5 (before forelimbs start)

Question 7

What are 2 other structures that are important for controlling locomotion?

Answer 7

-basal nuclei: subcortical structure
-cerebellum
*neither have UMN or LMN=don’t control the movements DIRECTLY just MODULATING

Question 8

Cerebellum:

Answer 8

-moderate and control motor movements
-ensuring the movements are appropriate for the task

Question 9

Proprioception travels to:

Answer 9

1. Cerebellum: modulate activity to make appropriate motor movements
   >doesn’t directly change LMNs, but acts on UMNs of brainstem and cerebral cortex
2. Thalamus to then the cerebral cortex

Question 10

Basal nuclei: (basal ganglia in primates=wrong name)

Answer 10

-group of subcortical nuclei (cell bodies) in the forebrain and midbrain
>intricate connections between nuclei
*functionally very important for motor control

Question 11

Basal nuclei importance for motor control:

Answer 11

-cognitive control of movements (net response to stimuli)
>initiating, sustaining, and terminating movements=*PLANNED MOVEMENTS
>postural control
*filters between appropriate and inappropriate movements (‘size of the movement’)

Question 12

Planned movement example of basal nuclei control/modulation:

Answer 12

-going to door waiting for a walk
-think: I want to go for a walk
-stand up and walk to the door (remember where it is)
-door opens, then goes outside
*all voluntary but it kind of just does all the actions as a package

Question 13

Basal nuclei receives input from:

Answer 13

-motor cortex
-feedback loop through thalamus back to cerebral cortex
*subcortical feedback loop
-cerebral cortex then initiates action via UMNs and LMNs

Question 14

Basal nuclei clinically not important in our domestic species, however in primates damage results in:

Answer 14

-abnormal motor controls
Ex. Parkinson’s, Huntington’s

Question 15

Yellow star thistle in horses:

Answer 15

-toxicity of horses
-damage to basal nuclei
>aren’t able to coordinate movements to prehend food=’starve’ to death
-they are hunger, they think about eating, but can’t initiate movements

Question 16

Lesions seen with damage to basal nuclei (humans);

Answer 16

-inability to initiate planned movements
-involuntary abnormal motor movements
-sequencing difficulties

Question 17

Examples of lesions to the basal nuclei in humans:

Answer 17

-Parkinson’s: difficulty initiating movements/sequencing
-Huntington’s: difficulty coordinating/spastic movements
-Tourette’s syndrome: uncoordinated motor movements or vocalizations
-OCD

Question 18

Opisthontonus:

Answer 18

-abnormal posture (spastic or rigid) due to activation of extensor muscles of neck, trunk and limbs
*due to severe cortical, brainstem or cerebellar disease
>arched back/neck
>head extended
>rigid limbs