Motor Control

Question 1

What is direct control of muscles via?

Answer 1

Alpha motor neurons in the spinal cord

Question 2

What control spinal reflexes?

Answer 2

Brainstem nuclei

Question 3

What four systems control movement?

Answer 3

Descending control pathways
Basal ganglia
Cerebellum and local spinal cord
Brain stem circuits

Question 4

What innervate muscles to initiate reflex and voluntary movements?

Answer 4

Lower motor neurons at cranial and spinal levels

Question 5

What happens to lesions at lower motor neurons at cranial and spinal levels?

Answer 5

Flaccid paralysis and muscle atrophy

Question 6

What regulates alpha motor neuron activity?

Answer 6

Upper motor neurons in brainstem or cortex synapse with multiple lower circuit neurons

Question 7

What neurons are the proximal shoulder muscles mapped to?

Answer 7

Medial motor neurons

Question 8

What happens if there is damage to sensory inputs?

Answer 8

Paralysis as if the motorneurons themselves had been damaged

Question 9

What nerve does the biceps jerk test?

Answer 9

C6

Question 10

What nerve is the triceps jerk reflex?

Answer 10

C7

Question 11

What nerve is the patellar tendon reflex?

Answer 11

L4

Question 12

What nerve is the achilles tendon reflex?

Answer 12

S1

Question 13

What do flexor or withdraw reflexes use?

Answer 13

Information from pain receptors in skin muscles and joints

Question 14

What do flexor or withdrawal reflexes do?

Answer 14

Withdraw part of the body war from painful stimuli and in towards the body

Question 15

What can increased sensory action potentials from pain receptors cause?

Answer 15

Increased activity in the flexor muscles of the affected part via a number of excitatory interneurons
Antagonistic extensors are inhibited

Question 16

What does excess load cause?

Answer 16

GTO reflex to be activated

Question 17

How can stretch reflexes be overridden?

Answer 17

Strong descending inhibition hyper polarises alpha motor neurons and the stretch reflex can’t be evoked

Question 18

What does activity of gamma motor neurons depend on?

Answer 18

Descending pathways - high activity causes muscle to become extremely resistant to stretch and is spastic

Question 19

What pathways control voluntary movements of distal muscles?

Answer 19

Lateral pathways

Question 20

What do ventromedial pathways control?

Answer 20

Posture and locomotion

Question 21

Where does 2/3rds of the cortocospinal tract originate?

Answer 21

Areas 4 and 6 of frontal motor cortex

Question 22

Where does the corticospinal tract decussate?

Answer 22

Medulla

Question 23

Where do the CST axons synapse?

Answer 23

Ventral horn motor neurons and interneurons to control muscles

Question 24

Where does the RST start?

Answer 24

Red nucleus of midbrain

Question 25

What happens if there are lesions in the CST and RST?

Answer 25

Fine movements of arms and hands lost | Can't move shoulders, elbows, wrists, fingers independently

Question 26

What happens if there is a lesion in the CST alone?

Answer 26

Same deficits but after a few months functions reappear as they have been taken over by RST

Question 27

Where do the ventromedial pathways originate?

Answer 27

Brainstem

Question 28

What do area 6 neurons drive?

Answer 28

Complex movements on either side of the body

Question 29

What is the function of the pre motor area of area 6?

Answer 29

Connects reticulospinal neurons innervating proximal motor units

Question 30

What is the function of the supplementary motor area of area 6?

Answer 30

Innervates distal motor units directly

Question 31

What does microstimulation in a specific area of the primary motor cortex elicit?

Answer 31

Coordinated movements of hand and mouth or movements that bring hands into central space to inspect/manipulate objects

Question 32

What ares generate the mental image of body in space?

Answer 32

Areas 5 and 7

Question 33

What happens when these areas are damaged?

Answer 33

Humans with damage have bizarre body images, may neglect or ignore one side of their body

Question 34

Where are decisions taken about what actions/movements to take and their likely outcome?

Answer 34

Prefrontal and parietal cortex

Question 35

What does cortical damage cause?

Answer 35

Immediate flaccidity of contralateral muscles - lift limb and release it drops passively

Question 36

What is initial hypotonia?

Answer 36

Spinal circuits deprived of cortical input when they regain function, the spare connections strengthen and new connections sprout

Question 37

What is Babinski's sign?

Answer 37

When the lateral side of dorsal foot is touched, plantar flexion should occur However in babies and those with cortical damage you see extension

Question 38

What is spasticity?

Answer 38

Increased muscle tone, hyperactive stretch reflex, clonus oscillatory contract muscles in response to stretch

Question 39

What are the features of upper motor neurone syndrome?

Answer 39

``` Injury site determines symptoms Initital hypotonia Babinski's sign Spasticity Loss of fine finger movements ```

Question 40

Where does subcortical input to area 6 come from?

Answer 40

Ventral lateral nucleus in dorsal thalamus

Question 41

What is the subcortical input called?

Answer 41

VLo, arises from basal ganglia

Question 42

What are the major components of basal ganglia?

Answer 42

Corpus striatum - caudate and putamen nucleus

Question 43

What receive excitatory cortical inputs on dendrites?

Answer 43

Medium spiny neurons in putamen and caudate

Question 44

What does the putamen fire before?

Answer 44

Limb/trunk movements

Question 45

What does the caudate fire before?

Answer 45

Eye movements

Question 46

Is the cortex to putamen inhibitory or excitatory?

Answer 46

Excitatory

Question 47

Is putamen to globus pallidus inhibitory or excitatory?

Answer 47

Inhibitory

Question 48

Is globus pallidus to Vlo neurons inhibitory or excitatory?

Answer 48

Inhibitory

Question 49

Is VLo to SMA inhibitory or excitatory?

Answer 49

Excitatory

Question 50

What is the effect of cortical excitation?

Answer 50

Excites putamen which inhibits the globus pallidus whichh release cells in VLo from inhibition so boosts SMA activity

Question 51

What do lesions to the cerebellum cause?

Answer 51

Uncoordinated inaccurate movements (Ataxia)

Question 52

What does the cortico-ponto-cerebellar projection connect?

Answer 52

Cortex, pontine nucleus and cerebellum