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BMS153 NEUROSCIENCE > motor control > Flashcards

motor control Flashcards

1
Q

lower motor neurons initiate

A

all movements produced by the skeletal musculature,

found in the spine

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2
Q

upper motor neurons

A

neurons that rise in the brainstem and cortex that control motor function

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3
Q

fritsch and hitzig 1870

A

using dogs demonstrated electrical stimulation of the part of the cortex elicits contraction of contralateral body muscles

known now as the primary motor cortex (percentile gyrus)

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4
Q

sherrington and penfield (early 1900s)

A

correlated the site of stimulation with the location of muscle contraction and demonstrated a topographic map similarl to the somatosensory one

proportions reflect density of innervation (and behavioural significance)

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5
Q

the motor pool

A

all the motor neurone innervating one particular muscle

they are grouped in rod-shaped clusters within the spinal cord extending over several vertebral segments

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6
Q

lower motor neurons innervate

A

the fibres of just one muscle

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7
Q

motor pools are organised

A

somatotopically

i.e. there is a map of the body’s musculature within the spinal cord

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8
Q

motor cortex upper motor neurons

A

concerned with fine control of more distal structures

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9
Q

brainstem upper motor neurons

A

project to medial motor pools primarily concerned with postural movement

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10
Q

upper body inputs

A

go lateral

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11
Q

lower body inputs

A

go medial

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12
Q

upper motor neurons

A

oringinate in motor cortex (outer layer of cerebrum)
their axons descend down to synapse with lower motor neurons in the brainstem or the spinal cord

and then out to lower motor neurones to control skeletal muscle contraction

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13
Q

longer upper motor neurone send axons to spinal cord

A

start in cerebral cortex (in grey matter outside of cerebrum)
and axon travel down through deep white matter of cerebrum
then through the midbrain, pons and medulla
then where brainstem meets spinal cord
axons will cross over to other side of spinal cord
until they reach the lower motor neurone

(cortico-spinal tract) - cerebal cortex to spinal cord

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14
Q

lower motor neurone in brainstem (cortico bulbar tract)

A

their axons through cranial nerves to skeletal muscle in head or neck

also cross over at brainstem to innervate opposite side of brainstem

but can innervate neutrons on the same side

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15
Q

cortico-bulbar tract

A

upper motor neurones in the cortex innervate the lower motor neurones in the brain stem
to control muscles of the head and neck

these axons may cross over to control the contra lateral side of the head and neck
but not always

can control both sides

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16
Q

hyperreflexia

A

increase in muscles stretch reflexes

upper motor neurone sign of dysfunction

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17
Q

clonnas

A

rhythmic contraction

antagonist muscles

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18
Q

lateral pathway example

A

axons on layer V cortical neurones (Betz cells)
project in the corticospinal tract
cross the midline at pyramidal decussation in the medulla
synapse on more laterally located mower motor neurone circuit in the spinal cord
controlling distal strucutres

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19
Q

ventromedial pathway

A

axons from brainstem project ipsilaterally in several tracts
e.g. vestibulospinal & reticulospinal

synapse on more medially located lower motor neuro circuits (MNs or internueons in spinal cord controlling more axial muscles)

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20
Q

cortical layers

A

90% of cortex is a six layer structure

main inputs are to stellate cells in layer IV

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21
Q

main outputs are from which cortical layers

A

III, V and VI

22
Q

where do the axons of the corticospinal tract derive from

A

large pyramidal or Betz cells in layer V of the cortical surface

23
Q

upper motor neurons of the motor cortex

A
  • for complex voluntary movements
  • project mainly contra laterally via corticospinal tract
  • also project via corticobulbar tract to hypoglossal nucleus in brain stem- controls movement of the tongue
24
Q

upper motor neurons in the brainstem

A

more concerned with maintenance of posture and balance

located in several nuclei inc
vestibular nucleus (vesitbular co ordination)
reticular formation
superior colliculus (visual co-ordination)

project ipsilaterally mainly to lower motor neurones controlling axial muscles concerned with maintaining posture

25
Q

main difference between upper and lower

A

upper MN always synapse on lower motor neurones (or their interneruon circuitry)
while lower MN always synapse directly on muscle fibres

26
Q

the anticipatory feed froward mechanism

A

Pre-adjusts body posture to compensate for the forces that will be generated when for example a level is lifted

27
Q

area 4 of brain

A

primary motor cortex

28
Q

area 6 of brain

A

medial and lateral premotor cortex

29
Q

2 routes for upper motor neurones to influence spinal cord circuits

A

1) anticipated by indirect projection via reticular formation to muscles
2) activation of voluntary movement direct to spinal cord via corticospinal tract

30
Q

the circuit of anticipation

A

from motor cortex to brainstem nuclei

31
Q

motor neuron disease

A

aKA amyotrophic lateral sclerosis (ALS)
degenerative disease of MN

can affect either super or lower MN

32
Q

lower motor neuron disease is characterised by

A

muscle paresis (weakness) or paralysis
loss of muscle tone due to loss of stretch reflexes
ultimately leads to severe muscles atrophy
patients usually die from lung dysfunction (due to atrophy of intercostal muscles)

33
Q

upper neurone disease characterised by

A

muscles weakness
spasticity due to increased muscle tone (no modulation of stretch reflex)
hyperactive reflexes
loss of fine voluntary movement
patients usually die from bulbar (tongue and pharynx) involvement

34
Q

role of basal ganglia and cerebellum

A

influence movement indirectly by regulating the function of upper motor neurons

35
Q

motor cortex

A

planning, initiating and directing voluntary movements

36
Q

brainstem centers

A

basic movements and postural control

37
Q

cerebellum

A

sensory motor coordination–> brainstem centers

38
Q

basal ganglia

A

gating proper intitiation of movement—> motor cortex

the motor cortex also connects to the basal ganglia
which in turn feedback to the premotor area (area 6) via the ventrolateral complex of the thalamus (VLo) to control initiation of movement
the ‘motor loop’

39
Q

basal ganglia components

A 
caudate
putamen
substantia nigra
subthalamic nucleus
globus pallidus
40
Q

the striatum

A

putamen and the caudate of the basal ganglia

41
Q

main input nuclei of the basal ganglia

A

caudate and putamen

42
Q

main output nuclei of the basal ganglia

A

the globus pallidus
and substantia nigra

send projections from basal ganglia to cerebral cortex via thalamus and to nuclei in the brainstem

43
Q

hypothesis of basal ganglia’s role in movement

A

the are different circuits within the basal ganglia that promote and inhibit movement respectively

44
Q

according to the hypothesis of the basal ganglia the main output of the structure is….?

A

inhibitory

neurons in the globus pallidus are constantly inhibiting the thalamus to prevent unwanted movements

45
Q

the direct pathway in the basal ganglia

A

when a signal to initiate movement is sent form the cortex to the basal ganglia

leading to silencing of neurone in the globus pallidus

this frees the thalamus from the inhibitory affects of the globes pallidus and allows movement to occur

46
Q

the indirect pathway in the basal ganglia

A

involves the sub thalamic nucleus and leads to increased suppression of unwanted movements

47
Q

huntingdons disease

A

degeneration of the striatum (putamen and caudate)
which results in reduced tonic inhibition of the thalamus (VLo) by the globes pallidus and increased initiation of inappropriate, rapid and jerky movements (hyperkinesis)

48
Q

the substantial nigra’s role

A

acts via the striatum to maintain balance between:

1) the activation of tonic inhibition of the VLo by the globus pallidus
2) the inhibition of the globus pallidus by the caudate and putamen in response to cortical input

49
Q

parkinson’s disease

A

degeneration in the substantia nigra upsets the balance of activity/inhibtion and leads to increased tonic inhibition of the Vlo by the GP and suppressed initiation of movement by the cortex (hypokinesis)

50
Q

where does the cerebellum receive info from

A

many areas of the cortex
corticopontocerebellar projection
sensory information from the spinal cord
vestibular system

in turn it projects back to the motor cortex via the thalamus
but has no direct output to spinal cord

51
Q

primary function of the cerebellum

A

detects and corrects differences between the intended movement and the actual movement -‘the motor error’

52
Q

lesions to cerebellum

A

causes cerebellar ataxis

poorly integrated movement

BMS153 NEUROSCIENCE (24 decks)

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