Motor Control 2

Question 1

How are lots of neurones involved in deciding a direction

Answer 1

As Each one has a preferred direction and will fire greater for a movement in that direction than any other

Question 2

Whats happens to the discharging neurones when you have a preferred direction

Answer 2

Neurones preferring that direction will fire more and others less resulting in a population vector.

Question 3

What controls the overall movement direction

Answer 3

Population vector encoded by the integrated activity of all the neurones.

Question 4

How does feedback occurs when you need to correct postural instability

Answer 4

Via vestibulo-spinal system
(brainstem vestibular nuclei to spinal cord motor neurones)

To correct postural instability

Question 5

How do you stabilise posture before movement occurs

Answer 5

Reticular formation via Reticulospinal tracts make feedforward anticipatory adjustment to stabilise posture before you make a move

Question 6

What is the symptoms of upper motor neurone syndrome/damage to descending motor pathway

Answer 6

Spinal shock - spinal cord deprived of cortical input

Babinskis sign

Spasticity

Loss of fine finger movements

Question 7

The symptoms of an upper motor lesion depends on what

Answer 7

Injury site

Question 8

What is the affect of cortical damage

Answer 8

Immediate flaccidity of contralateral muscle - have no drive

Question 9

What occurs after spinal shock in upper motor lesion that leads to the return of reflexes

Answer 9

Days later spinal circuits regain function - spared connections strengthen and new connections sprout.

A consistent pattern of motor signs emerges

Question 10

What is seen in spasticity

Answer 10

Increased muscle tone

hyperactive stretch reflex

Clonus oscillatory contract/relax muscles in reponse to stretch

Question 11

Why does spasticity occur in upper motor lessons

Answer 11

Due to removal of cortical suppressive influences

Question 12

What does Babinskis sign indicate

Answer 12

Incomplete upper control of spinal circuits

Question 13

What is the overall pathway of the motor loop

Answer 13

Communication occurs from motor cortex to the basal ganglia then to ventral lateral nucleus in dorsal thalamus (VLo) then back to the supplementary areas in the cortex area 6

Question 14

What part of the cortex targets the basal ganglia motor loop

Answer 14

Frontal (motor cortex4+6)
Prefrontal
Parietal (sensory cortex)

Question 15

What is the overall function of the cortical activation of basal ganglia

Answer 15

Part of a motor loop with the function of a Positive Feedback Loop which focusses widespread cortical activation onto the Supplementary Motor Area

Question 16

What two pathway does information from the motor cortex reach the spinal cord

Answer 16

Lateral pathway (red nucleus)

Ventromedial pathway
reticular nuclei and superior colliculus and vestibular nuclei

Question 17

What is the major component of the basal ganglia

Answer 17

Corpus striatum

Question 18

What is the corpus striatum

Answer 18

two principal nuclei the caudate and the putamen

Question 19

What is the function of the corpus striatum

Answer 19

Input zone of the basal ganglia receiving input from all over the cortex in the motor loop

Question 20

What is the pathway to the basal ganglias corpus striatum called

Answer 20

corticostriatal pathway - multiple parallel pathways with different functions

Question 21

What type of neurones are in putamen and caudate

Answer 21

Medium spiny neurones- which have large dendritic trees in to intergrate signals

Question 22

Where do the medium spiny neurones of the putamen and caudate receive signals from

Answer 22

Somatosensory, premotor and motor cortical inputs

Question 23

What cortical inputs are received by the medium spiny neurones dendrites

Answer 23

excitatory glutamatergic

Question 24

What are the axons of the medium spiny neurones

Answer 24

Inhibitory - GABAergic

Question 25

Where do the axons of the medium spiny neurone in the putamen project

Answer 25

Globus pallidus

Question 26

Where do the axons of the medium spiny neurone in the caudate project

Answer 26

substantia nigra pars reticulata

Question 27

When does the putamen fire its axons

Answer 27

Before limb/trunk movements (predictive)

Question 28

When does the caudate fire its axons

Answer 28

Before eye movements | predictive

Question 29

What is the exact process of the motor loop: cortex - basal ganglia - cortex

Answer 29

Cortex excites putamen Putamen inhibits Globus Pallidus Globus Pallidus stops inhibiting thalamus VLo neurons VLo neurons boost SMA activity

Question 30

What happens at rest of globes pallidus neurones

Answer 30

Spontaneously active and inhibit VLo

Question 31

What arrangement is present in the basal ganglia to gate the operation of the motor loop

Answer 31

A chain of neurones arranged in dis-inhibitory circuit

Question 32

What is the two pathways in the basal ganglia

Answer 32

Direct - promote movement in SMA Indirect - suppressing competing actions to the one direct pathway

Question 33

How does the indirect pathway suppress the competing actions

Answer 33

The Putamen+caudate (striatum) inhibits the globes pallidus external which further inhibits GPi and Subthalamic Nuclei (STN)

Question 34

What occurs when cortex excites the STN

Answer 34

Excites GPi which inhibits the thalamus

Question 35

What is two basal ganglia disorders

Answer 35

Parkinsons Huntingtons

Question 36

What is the cause of parkinson

Answer 36

degeneration of neurones in substrantia nigra (SN) and their dopaminergic (excitatory) inputs to the striatum

Question 37

What is the symptoms of Parkinsons

Answer 37

Hypokinesia: Slowness Difficulty making voluntary movements Increased Tone Tremors of hand & jaw

Question 38

What is dopamine affect on cortical inputs

Answer 38

Enhance cortical inputs the direct pathway Suppress inputs through indirect pathway

Question 39

What is the affect of depleted dopamine in motor control

Answer 39

Close down actions funnelled through the thalamus to the SMA

Question 40

What is the symptoms of huntingtons disease

Answer 40

Hyperkinesia Dementia Personality Disorders Characteristic chorea

Question 41

What is seen in characters chorea

Answer 41

Spontaneous, uncontrolled, rapid flicks and major movements with no purpose

Question 42

What is the cause of Huntington's

Answer 42

A heredity disease cause by the profound loss of caudate, putamen and globes pallidus

Question 43

What is the affect of the profound loss of the basal ganglia in huntington's disease

Answer 43

loss of the ongoing inhibitory effects of the basal ganglia

Question 44

How much of the brain volume and CNS neurones if the cerebellum made off

Answer 44

Cerebellum is 10% of brain volume and 50% of CNS neurones

Question 45

What can lesions of the cerebellum lead to

Answer 45

Uncoordinated inaccurate movements - ataxia

Question 46

What is another cause of ataxia with the cerebellum

Answer 46

Cerebellar depression by alcohol

Question 47

What information does the cerebellum send the cortex

Answer 47

Instructions on direction, timing and force of movements

Question 48

What is the cortico-ponto-cerebellar projection

Answer 48

Connects the cortex, pons and cerebellum as the cerebellum connects to the cortex via the ventrolateral thalamus

Question 49

Where does the motor loop go after basal galena and VLo to achieve refinement

Answer 49

by a feedback loop through pons, cerebellum, thalamus and back to the cortex

Question 50

How does this cortico-ponto- cerebellar projection provide refinement of motor loop

Answer 50

It makes use of motor learning stored in the cerebellum, based on predictions, calculations and experience, comparing what was intended to what happens then compensating.