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Neuroscience > Sensorimotor system > Flashcards

Sensorimotor system Flashcards

1
Q

how is the sensorimotor system organised

A

hierarchically
functional segregation (each level comprised of different units)
motor input is guided by sensory input (sensory feedback)

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2
Q

ballistic movements

A

only response not mediated by sensory feedback

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3
Q

learning

A

changes the nature and locus of sensorimotor control

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4
Q

hierarchy

A 
association cortex (top)
secondary motor cortex
primary motor cortex
brain stem and motor nuclei 
spinal motor circuits (bottom)
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5
Q

sensorimotor association cortex

A

receives input from 3 somatosensory systems:
visual system
auditory system
somatosensory system

has different segments that control different sections of the body

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6
Q

before movement is initiated, what is needed?

A

original muscle location

external objects location

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7
Q

damage to the association cortex

A

apraxia - disorder of voluntary movement

contralateral neglect - struggle to respond to stimuli on on opposite side of body to image

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8
Q

dorsolateral prefrontal association cortex

A

initiates voluntary movement - interacts with prefrontal association cortex and frontal areas

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9
Q

where does the secondary motor cortex receive input from?

A

association cortex

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10
Q

where does the secondary motor cortex send information?

A

primary motor cortex and secondary motor areas

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11
Q

divisions of the secondary motor cortex

A

8 areas with own subdivisions:

3) different supplementary motor areas (SMA, preSMA & supplementary eye field)
2) premotor areas (dorsal and ventral)
3) small areas (cingulate motor areas)

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12
Q

frontal eye field

A

controls eye movement

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13
Q

mirror neurons

A

fire when a particular goal directed hand movement is done, or when it is observed

  • mechanism for social cognition?
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14
Q

primary motor cortex

A

organised somatotopically - body parts map onto it
-> motor homunculous

two different hand areas in PMC - one for stereognosis

complex species specific movements which involve several parts of the body

neurons initiate movement

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15
Q

primary motor cortex lesions

A

astereognosia - deficits in stereognosis

  • speed, accuracy and force of patients movements
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16
Q

cerebellum

A

interact with different levels of the hierarchy

used for motor learning (sequences)
correcting ongoing movement

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17
Q

cerebellum information in

A

primary and secondary motor cortex
descending motor signals
feedback

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18
Q

damage to the cerebellum

A 
no precise movements
force
velocity 
amplitude
posture
balance
gait
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19
Q

basal ganglia

A

collection of interconnected nuclei

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20
Q

what does the basal ganglia do?

A

modulatory function - adjustment of movement

habit learning

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21
Q

how does the basal ganglia work?

A

carries information in loops from motor cortex via the thalamus

22
Q

dorsolateral corticospinal tract

A 
direct - straight to spinal cord
synapses on interneurons of spinal grey matter (distal muscles)
- hands
- wrists
- fingers
23
Q

betz cells

A

large pyramidal neurons of the primary motor cortex

24
Q

dorsolateral corticorubrospinal tract

A

indirect - brain stem then spinal cord

synapses in red nucleus controlling cranial nerves (face) and on motor neurons (arms and legs)

25
Q

ventromedial corticospinal tract

A

direct - long axons descending from PMC

each axon branches out innervating interneuron circuits in several spinal regions

26
Q

ventromedial cortico-brainstem-spinal tract

A

indirect - axons feed into network of brain structures
control proximal muscles (trunk and limbs)

interacts with 4 major brain regions:

  • tectum (auditory and visual info)
  • vestibular nucleus (balance)
  • reticular formation (species typical movement)
  • motor nuclei of cranial nerves (face)
27
Q

differences between the two pathways

A

ventromedial tracts more diffuse (as they innervate interneurons)

ventromedial tract projects to the trunk and limbs rather than the distal muscles

28
Q

motor units

A

single motor neuron and all of the skeletal fibre muscles that innovate it

29
Q

motor neuron

A

controls the motor unit

30
Q

skeletal muscles

A

tendons (muscle fibres bound together in a tough membrane)

31
Q

acetylcholine

A

causes fibres to contract

released at neuromuscular junctions

32
Q

motor pool

A

all of the motor neurons that innovate the fibres of a muscle

33
Q

flexors

A

bend or flex a joint

34
Q

extensors

A

straighten or extend

35
Q

fast muscle fibres

A

contract and relax quickly

short term as poorly vascularised

36
Q

slow muscle fibres

A

slow but maintained

37
Q

synergistic muscles

A

contraction produces the same movement

38
Q

antagonistic muscles

A

act in opposition

39
Q

dynamic contraction

A

increase muscle tension by shortening and pulling together the muscle

40
Q

isometric contraction

A

increases density without shortening

increases neurons firing within it

41
Q

golgi tendon organs

A

embedded in tendons
connect skeletal muscles to bone
respond to muscle tension

42
Q

muscle spindles

A

embedded in muscle
respond to change in muscle length
each muscle has its own muscular spindle feedback circuit - stops things from altering body position

43
Q

intrafusal muscle

A

stops muscle falling slack each time its skeletal muscle (extrafusal) contracts

responds to small changes because of this

44
Q

withdrawal reflex

A

1.6 milliseconds (time to cross one synapse)

45
Q

stretch reflex

A

patellar tendon reflex - stretches the tendon and therefore thigh muscle

46
Q

reciprocal inhibition

A

allows a smooth contraction (one muscle is contracted, another relaxes)

47
Q

cocontraction

A

smooth movements produced with precision by a slight contraction of one of the antagonistic muscles

48
Q

recurrent colateral inhibition

A

inhibitory neurons give muscle fibres a break

each motor neuron synapses onto a Renshaw cell

49
Q

renshaw cells

A

give the neurons this break

50
Q

with practice:

A

response chunking - practice combines individual movements into patterns

shifting control to lower levels of the hierarchy

51
Q

motor equivalence

A

doesn’t always use the same muscles to get the end goal movement

52
Q

fentress

A

rats shoulder muscles move as if they have had legs, even when they have been amputated from birth

Neuroscience (15 decks)

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