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control of human movement > spinal cord+descending tracts, motor cortex and cerebellum > Flashcards

spinal cord+descending tracts, motor cortex and cerebellum Flashcards

1
Q

where are alpha motor neurons located?

A

anterior horn of spinal cord, grey matter, and part of somatic motor system (voluntary movement)

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2
Q

function of alpha motor neurons in spinal cord

A
  • initiate muscle contractions
  • release acetylcholine at junctions to activate muscle fibres
  • contraction of skeletal muscle then alpha motor neurons are essential for voluntary movement
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3
Q

what do alpha neurons form?

A
  • make up motor units (alpha motor neuron and all muscle fibres it innervates)
  • small motor units for finer movements and larger for more force
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4
Q

cerebellums role

A
  • modulate motor output and refines voluntary movement
  • adjustor of motor control systems
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5
Q

what ways does the cerebellum contribute to motor control

A
  1. coordination and precision
  2. error detection and correction
  3. motor learning
  4. posture and balance
  5. timing and rhythm
  6. feedforward control
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6
Q

what makes up the 31 Paris of spinal nerves

A
  • 8 cervical
  • 12 thoracic
  • 5 lumbar
  • 5 sacral
  • 1 coccygeal
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7
Q

anatomy of the spinal nerves

A
  • each nerve has a neural (motor) and dorsal sensory) root
  • consists of grey and white matter
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8
Q

what does grey matter consist of?

A
  • H shaped structure
  • anterior and posterior horns
  • alpha motor neurons in anterior horn
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9
Q

what does white matter consist of?

A
  • myelinated nerve fibres and bundled into tracts carrying sensory info up and motor info down spinal cord
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10
Q

name the 6 descending fibre systems to the spinal cord

A
  1. corticospinal tract
  2. rubrospinal tract
  3. reticulosppinal tract
  4. vestibulospinal tract
  5. tectospinal tract
  6. corticobulbar tract
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11
Q

corticospinal tract

A
  • origin: primary motor cortex
  • function: voluntary, fine motor control of muscles
  • largest descending tract
  • direct and indirect connections to motor neurons
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12
Q

rubrospinal tract

A
  • origin: red nucleus, brainstem
  • midbrains collection of cell bodies
  • function: motor control and coordination
  • highly vascularised- inputs from cerebellum and primary motor cortex
  • activation of flexor motor neurons
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13
Q

reticulospinal tract

A
  • origin: reticular formation in brainstem
  • function: muscle tone modulation, reflex activity and autonomic functions (involuntary)
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14
Q

tectospinal tract

A
  • coordinates head and eye movements in response to visual stimuli
  • axons travel down spinal cord
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15
Q

vestibulospinal tract

A
  • origin: vestibular nuclei in brainstem
  • function: regulates posture and balance
  • contracts and relaxes muscles to maintain balance, posture and muscle head movements
  • innervates neck and controls eye movements
  • excitation of extensors and inhibition of flexors
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16
Q

corticobulber tract

A
  • controls facial muscles and head through connections with cranial motor nerve nuclei
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17
Q

which tracts make up the lateral descending system?

A
  1. corticospinal tract
  2. rubrospinal tract
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18
Q

which tracts make up the medial descending system?

A
  1. reticulospinal tract
  2. vestibulospinal tract
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19
Q

pathway of the corticospinal tract

A
  • 90% are lateral
  • through internal capsule, cerebral pundicles and pyramids of the medulla oblongata before crossing onto contralateral side
  • continue down spinal cord as lateral tract controls limbs and anterior tract controls axial muscles
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20
Q

corticobulber tract pathway

A
  • upper motor neurons project from cerebral cortex to brainstem via cerebral peduncles and innervates interneurons/cranial nerves
  • interneurons innervate reticular formation
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21
Q

rubrospinal tract pathway

A
  • axons descend in the lateral funiculus of spinal cord
  • fibres terminate on interneurons projecting to ventral horn
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22
Q

reticulospinal tract pathway

A
  • medial and lateral tracts
  • medial = arises from pons and projects ipsilaterally to entire spinal cord. facilitates extensor spinal reflexes
  • lateral = arises from medulla and projects bilaterally to spinal cord. surpasses extensor activity
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23
Q

vestibulospinal tract pathway

A
  • medial and lateral tracts
  • medial = arises from ipsilateral and contralateral medial vestibular nuclei at non-medulla junction
  • descends in ventral funiculus of cervical spinal cord and terminates in ipsilateral ventral horn
  • lateral = arises from neurons of lateral vestibular nucleus at pons-medulla junction. descends entire length of spinal cordoned receives inhibitory pints from cerebellum
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24
Q

describe the motor cortex

A
  • region of the cerebral cortex
  • planning, controlling and executing voluntary movements
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25
Q

primary motor cortex (M1)

A
  • location: precentral gyros of the frontal lobe
  • execution of voluntary movements by sending signals to muscles on contralateral side of the body
  • somatotopically organised
26
Q

premotor cortex

A
  • location: anterior to primary motor cortex
  • planning and coordinating movements- receives info from sensory areas to organise motor movements
27
Q

supplementary motor area (SMA)

A
  • location: medial surface of hemisphere
  • plan and execute complex movements
  • coordinates bilateral movements and both sides of body
28
Q

how many neurons are there in the brain?

A

86 billion neurons in the brain

29
Q

explain the cerebellums rule of 3?

A
  • 3 of everything
  • 3 lobes (anterior, posterior, flocculonodular)
  • 3 functional subdivisions
  • 3 pairs of peduncles
  • 3 pairs of deep nuclei
  • 3 cortical layers
30
Q

the cerebellum?

A
  • 10% of the brains volume
  • coordination, maintenance of posture, maintenance of muscle tone/balance and motor learning
31
Q

cerebellums coordination and precision function

A
  • receives input from the sensory systems, and visual and vestibular info
  • inputs help cerebellum fine-tune motor commands for accurate and smooth movement
32
Q

cerebellums error detection and correction function

A
  • compares intended motor output from motor cortex with actual feedback received from body’s sensory systems
  • if error, it sends corrective signal to adjust allowing precise movements
33
Q

cerebellums motor learning function

A
  • stores motor memories and adjusts future movements based on past experiences
  • essential for learning new skills and refine original patterns with practice
34
Q

cerebellums posture and balance function

A
  • receives info about body’s position and orientation in space and integrates this info to modulate muscle activity ensuring stability during movements
35
Q

cerebellums timing and rhythm function

A
  • coordinates timing of muscle contractions
  • smooth and well-timed execution of complex movements
36
Q

cerebellums feedforward control function

A
  • predicting the consequences of motor commands allowing for adjustments before the movement occurs
37
Q

was is ataxia cerebellar damage

A
  • abnormal execution of multi-jointed voluntary movements due to lack of coordination
  • caused by stroke, MS, tumours
  • unsteady and clumsy
  • struggles with precise motor control like walking, reaching and fine movements, movement can appear jerky
38
Q

dysmetria cerebellar damage

A
  • type of ataxia
  • lack of coordination = inability to control range of movement and judge distance
  • overshoot or undershoot targets
39
Q

major components of cerebellum?

A
  1. cerebellar peduncles
  2. cerebellar cortex
  3. deep cerebellar nuclei
40
Q

what are the cerebellar peduncles?

A
  • bundles of axons connecting cerebellum to other parts of CNS facilitating coordination, communication and motor functions
  • superior, middle and inferior
41
Q

superior peduncle

A
  • dorsal aspect of brainstem
  • carry efferent fibres, transmit signals to midbrain and thalamus
  • motor coordination and control
  • crossing of fibres in midbrain
42
Q

middle peduncle

A
  • located in ventral aspect of pons
    -afferent fibres carrying input from cerebral cortex to cerebellum
  • convey info about planned/ongoing movements
  • learning and integration of sensory info
43
Q

inferior peduncle

A
  • dorsal aspect of medulla oblongata
  • afferent and efferent fibres carrying input from spinal cord to cerebellum
  • output info to vestibular nuclei and reticular formation influencing balance, posture and coordination
44
Q

what is the cerebellar cortex?

A
  • neural circuitry integrating inputs from cortex, brainstem and spinal cord
  • modulates motor outputs
45
Q

cerebrocerebellum

A
  • largest, protects to and from cerebral cortex
  • planning and execution of voluntary movement
  • connected with cerebral cortex especially motor planning and coordination areas
46
Q

major components of cerebellar cortex

A
  • cerebrocerebellum
  • spinocerebellum
  • vestibulocerebellum
47
Q

spinocerebellum

A
  • coordination of muscle activity and maintenance of posture
  • input from spinal cord
48
Q

vestibulocerebellum

A
  • control of balance and eye movements
  • input from vestibular system
49
Q

main components of the deep cerebellar nuclei

A
  1. dentate
  2. interposed
  3. fastigial
50
Q

dentate

A
  • most lateral
  • in cerebrocerebellum
  • output to motor cortex via superior peduncle and thalamus
51
Q

interposed

A
  • located in intermediate cortex od spinocerebellum
  • output to red nucleus via superior peduncle
52
Q

fastigial

A
  • most medial
  • output to spinal cord and vestibular nucleus
53
Q

what does cerebellar circuitry involve?

A
  • multiple layers of neurons and cell types with intricate circuitry
  • highly folded structure = folia
54
Q

main components of the cerebellar circuitry

A
  1. mossy fibres (granule layer)
  2. granule cells (granule layer)
  3. climbing fibres (granule layer)
  4. purkinje cells (purkinje cell layer)
  5. parallel fibres (molecular layer)
55
Q

what are purkinje cells?

A
  • cell body and vast dendrite tree
  • dendrites receive afferent input from parallel fibres and climbing tree
  • output to deep cerebellar nuclei
  • cerebellar output via purkinje cells
  • inhibitory function
56
Q

mossy fibres

A
  • primary neurons carrying info Tinto cerebellum
  • activate granule cells and cellebellar nuclei
57
Q

granule cells

A
  • attach to parallel fibres which synapse with dendrites of prukinje cells
58
Q

climbing fibre

A
  • only one
  • excites purkinje cells directly
  • originates in inferior olive
  • senses error signals to elicit learning
59
Q

conditioned blink eye response

A
  • UCS elicits reflex response causing an UCR
  • sufficient number of paired association CS elicits CR and attenuates UCR
60
Q

Marr-Albus-Ito hypothesis

A
  • mechanism underpinning eye-blink response
  • associative learning
  • simultaneous activation of climbing fibres and mossy fibres causes long-term changes in parallel fibre to purkinje synapses, resulting in long term depression
  • as purkinje cells are inhibitory, LTD increases output of deep cerebellar nuclei

control of human movement (10 decks)

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