Motor Control

Question 1

What are the different pathways in which the brain is connected to the spinal cord for motor innervation?

Answer 1

Ventral pathways - corticospinal tract & rubrospinal tract
Ventromedial pathways - tectospinal tract, vestibulospinal tract & pontine and medullary reticulospinal tract

Question 2

What would be lost if there was a lesion of the corticospinal tract and the rubrospinal tract?

Answer 2

Loss of fine movements of arms, hands

Can move shoulders, elbows, and fingers independently

Question 3

What would be lost if there was lesion of the corticospinal tract but not the rubrospinal tract?

Answer 3

Loss of fine movements and moving limbs independently

However these functions would re appear after a few months as the Rubrospinal tract would take over

Question 4

How do you refine voluntary movements ?

Answer 4

Motorneurones from the motor cortex both excite and inhibit agonist and antagonist muscles monosynaptically

Question 5

Where does the corticospinal tract originate?

Answer 5

2/3rd area 4 & 6

1/3rd is somatosensory

Question 6

Where does the rubrospinal tract originate?

Answer 6

Red nucleus of midbrain

Question 7

Where does the pontine and medullary reticulospinal tract originate?

Answer 7

The brainstem

Question 8

What ventromedial pathway is responsible for ensuring eyes remian stable when the body moves?

Answer 8

Tectospinal tract

Question 9

What ventromedial pathway is responsible for stabalising the head?

Answer 9

The vestibulospinal tract

Question 10

What ventromedial patwhay is responsible for maintaining balance and body position?

Answer 10

Pontomedullary reticulospinal tract

Question 11

Where does axons from the corticospinal tract synapse?

Answer 11

Dorsal horn

Question 12

What areas are responsible for planing and controlling precise movements?

Answer 12

Primary cortex (area 4)
Pre motor cortex (area 6)

Question 13

What is area 6 sub divided into?

Answer 13

Pre motor area

Supplementary motor area

Question 14

Regarding area 6, what ‘sub area’ innervates distal motor neurones directly? And which one innervates proximal motor units?

Answer 14

Proximal = pre motor area
Distal = supplementary area

Question 15

What area is responsible for proprioception?

Answer 15

Posterior parietal cortex ( area 5 and 7)

Question 16

If we only think about movements but done carry them out what part of our brain is active?

Answer 16

Area 6

Area 4 is the area for doing it by activating neurones of the CST and RST

Question 17

What does it mean by there is a feedforward mechanism that controls movement?

Answer 17

Before there is a change in body position, brainstem reticular formation nuclei (controlled by the cortex) initiate feedforward anticipatory adjustments to stabilise posture

Question 18

What are the clinical signs of upper motor neurone syndrome?

Answer 18

Initial hypotonia - spinal shock
Immediate flaccidity of contralateral muscles

Days later spinal circuits regain function as spared connections and new connections sprout
Babski’s sign - plantar flexion
Hypertonic - spasticity , clonus
Hyperreactive reflexes 
Loss of fine finger movements

Question 19

What is the main function of the basal ganglia?

Answer 19

Initiation of voluntary movements

Question 20

What are the names of the basal ganglia?

Answer 20

Corpus striatum - putamen and globus pallidus
Caudate
Substantia nigra

Question 21

Where does motor subcortical input to area 6 come from?

Answer 21

Ventral lateral nucleus in dorsal thalamus

Question 22

Where does basal ganglia recieve information from?

Answer 22

Pre frontal, frontal and parietal cortex’s

Question 23

Which pathway through he spinal cord does the basal ganglia follow before it sends information to the VLo?

Answer 23

corticospinal tract

Question 24

What basal ganglia are excitatory and inhibitory?

Answer 24

Putamen and caudate = excitatory

Globus pallidus and substantia nigra = inhibitory

Question 25

What is the difference in the direct and indirect pathway of the basal ganglia?

Answer 25

Direct pathway - positive feedback loop to initiate the ‘go’ signal Indirect pathway - antagonises the direct loop

Question 26

Name 2 basal ganglia disorders.

Answer 26

Huntington’s | Parkinson’s

Question 27

What is Parkinson’s caused by?

Answer 27

Degeneration of neurones in substantia nigra and their dopaminergic (excitatory) inputs to the striatum

Question 28

What is the clinical presentation of Parkinson’s?

Answer 28

Hypokinesia - slowness, difficulty to make voluntary movements Increased muscle tone Tremor of hands and jaw

Question 29

What is the clinical presentation of Huntington’s disease?

Answer 29

Hyperkinesia with dementia and personality disorders | Spontaneous uncontrolled rapid flicks and major movements

Question 30

What pathways are affected in Parkinson’s and Huntington’s?

Answer 30

Both the direct and indirect pathways are affect in Parkinson’s and Huntington’s

Question 31

What does lesions to the cerebellum produce?

Answer 31

Uncontrolled inaccurate movements Ataxia - unable to touch nose with eyes shut Similar to alcohol which suppresses cerebellar circuits.

Question 32

The signals for fine tuning of muscular contraction from the thalamus are travelled to the cortex via what?

Answer 32

Ventrolateral thalamus (VLo)

Question 33

What is the main function of the cerebellum?

Answer 33

Direction, timing and force - fine tuning of muscular contraction

Question 34

what is the corpus striatum and their function?

Answer 34

included 2 principle basal ganglia: - caudate and the putamen they are the input zones of the basal ganglia

Question 35

through which pathway does the corpus striatum receive inputs?

Answer 35

corticostriatal pathway

Question 36

the corpus striatum is predictive of movements. | what specifically do they do that makes them predictors of movements?

Answer 36

the putamen the fires limb/trunk movements the caudate fires before eye movements

Question 37

describe the motor loop regarding basal ganglia?

Answer 37

cortex to putamen = excitatory putamen to globus pallidus = inhibitory globus pallidus - Vlo = inhibitory Vlo - SMA = excitatory

Question 38

where does information received from the basal to the Vlo send it to?

Answer 38

the supplementary motor area in the cortex

Question 39

why does inhibition of the globus pallidus cause excitation of the Vlo to SMA?

Answer 39

at rest globus pallidus neurones are spontaneously active and inhibit Vlo inhibition of globus pallidus therefore releases the Vlo from inhibition = excitation from Vlo - SMA

Question 40

Where does the pyramidal tract decussate?

Answer 40

Lower level part of the medulla at the decussation of the pyramids

Question 41

Where does the pyramidal tract originate?

Answer 41

Frontal lobe, pre central gyrus, area 4

Question 42

If there is damage to the pyramidal tract what would be lost?

Answer 42

Motor function

Question 43

If there is an UMN lesion, why does this cause increased reflexes?

Answer 43

A knee jerk is a monosynaptic reflex mediated at the level of the spinal cord by the LMN. UMN are tonically inhibitory to the LMN. Therefore when these UMN are damaged there is no inhibition of the LMN so the reflexes become increased