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ANAT2005 > Control of Movement > Flashcards

Control of Movement Flashcards

1
Q

Alpha motor neurons of the spinal cord receive input from what 3 major sources?

A
  1. pyramidal tract & extrapyramidal tracts
  2. muscle sensory systems
  3. spinal interneurons
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2
Q

What do alpha motor neurons do with the input they receive from their three major sources?

A
  • convey this information to skeletal muscles to initiate movement
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3
Q

What is the cerebral cortex?

A
  • the highest centre for control of voluntary movements
  • controls all skeletal muscles through the pyramidal pathways
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4
Q

Supraspinal reflexes are induced by which CNS tract?

A
  • extrapyramidal tracts
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5
Q

What distinguishes the pyramidal and extrapyramidal tracts, and what comprises them?

A

Pyramidal:
- from cortex
- pass through pyramids of medulla
- for conscious movements
1. corticospinal tract
2. corticobulbar tract
Extrapyramidal:
- from brainstem
- do not pass through pyramids of medulla
- for unconscious (reflexive) movements
1. tectospinal tract
2. rubrospinal tract
3. reticulospinal tract
4. vestibulospinal tract

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6
Q

What is the motor cortex, and what are its divisions?

A
  • the highest centre for voluntary movement
  • located in the frontal lobe
    can be divided into:
    1. primary motor cortex (M1)
    2. premotor (secondary) cortex
    i. pre-motor area
    ii. supplementary
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7
Q

What is the motor cortex, and what are its divisions?

A
  • the highest centre for voluntary movement
  • located in the frontal lobe
    can be divided into:
    1. primary motor cortex (M1)
  1. premotor (secondary) cortex
    i. pre-motor area
    ii. supplementary area
  2. prefrontal cortex
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8
Q

Discuss the anatomy of the prefrontal cortex

A
  • located in the frontal pole and encompasses most of the rostral cortical part of the frontal lobe
  • is the highest order association cortex of the frontal lobe, and highest level of all cerebral cortices
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9
Q

Discuss the function of the prefrontal cortex broadly, and then the function of its lateral, orbital and medial components.

A
  • does not directly regulate motor control, however acts as an executive function centre, of which motor is one

Lateral PFC: rational thinking, planning and problem solving
Orbital PFC: control emotional behaviour
Medial PFC: sustaining attention, detecting error in own social misconduct

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10
Q

Discuss the anatomy of the supplementary motor cortex

A
  • anterior to pre central gyrus
  • middle-order association cortex
  • contributes to pyramidal pathway
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11
Q

Discuss the functions of the supplementary motor cortex

A
  • contributes to learning sequence of movements, and bilateral coordination
  • stores skilled memory: contributes to mental rehearsal of movement
  • important for speech (sequencing of movements for sounds/speech)
  • initiates movements specified by internal cues (self-generated) rather than externally delivered cues
  • works more closely with basal ganglia
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12
Q

Discuss the anatomy of the premotor cortex

A
  • is located anterior to precentral sulcus, but only on lateral surface of the hemispheres
  • is a middle order association motor cortex
  • contributes to pyramidal pathway
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13
Q

Discuss the functions of the premotor cortex

A
  • integrates sensory information into motor plans (sensorimotor transformation)
  • modulates movement
  • dorsal parietal (sensory) cortex is important in transformation of somatosensory and visual information into relevant motor commands
  • anticipates voluntary movement, hence coordinates on-going movements
  • reacts more to externally delivered cues and works more closely with the cerebellum
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14
Q

Discuss the location of the primary motor cortex, and define the ‘motor homunculus’

A
  • located in the pre-central gyrus (most caudal part of frontal lobe and rostral to the central sulcus)
    Motor homunculus: the size of cortical surface responsible for a part of the body is proportional to the degree of motor control exercised in that part
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15
Q

Discuss the functions of the primary motor cortex (M1)

A
  • execution of movements/motor outputs (contributes to pyramidal pathway)
  • contains the giant cells of Betz in layer V of the cortex
  • is somatically organised as the motor cortex
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16
Q

Discuss the features of the lateral corticospinal tract vs. the anterior cortical tract.

A

Lateral (90% of corticospinal tract):
- innervates the limbs (distal more than proximal)
- most fibres originate from the motor cortex and terminate in the ventral horn of the spinal cord
- targets alpha motor neurons that feed into the brachial and lumbosacral plexuses
- terminate at the cervical and lumbosacral levels

Anterior (10% of corticospinal tract):
- innervates axial muscles
- synapses with alpha motor neurons that are located at spinal levels C1-C4 and T1-T12
- does not decussate at the pyramidal decussation, but rather decussates at the various spinal levels listed above

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17
Q

Which structures of the limbic lobe are involved in declarative (explicit) memory?

A
  • hippocampus and surrounding cortical areas
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18
Q

Which structures of the brain are involved in nondeclarative (Implicit) memory?

A
  • basal ganglia motor areas of cortex, and cerebellum
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19
Q

Which structures of the brain are involved in nondeclarative (Implicit) memory?

A
  • basal ganglia motor areas of cortex, and cerebellum
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20
Q

Which structures of the brain are involved in nondeclarative (Implicit) memory?

A
  • basal ganglia motor areas of cortex, and cerebellum
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21
Q

What is the role of the amygdala?

A
  • centre for fear in brain
  • perception of fear
  • expression of fearful behaviour
  • acquisition of fear in response to stimuli
  • provides emotional component to learning process
  • involved in regulating stress effects on memory
  • focusing on faces and emotions (during social interaction)
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22
Q

What is the role of the amygdala?

A
  • centre for fear in brain
  • perception of fear
  • expression of fearful behaviour
  • acquisition of fear in response to stimuli
  • provides emotional component to learning process
  • involved in regulating stress effects on memory
  • focusing on faces and emotions (during social interaction)
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23
Q

What are some diseases associated with impaired amygdala function?

A
  • phobias
  • autism
  • schizophrenia
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24
Q

What are the three longitudinal substructures comprising the brainstem?

A
  1. tectum - most posterior part of the brainstem
  2. tegmentum - (floor of brainstem ventricles) is the middle part of the brainstem
  3. base is the most anterior part of the brainstem
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25
Q

What are the features of the midbrain that are important in motor function (particularly movement and coordination)?

A
  • the substantia nigra, the red nucleus, and the superior colliculi
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26
Q

Where do axons of the pontine nuclei enter the cerebellum?

A
  • via the middle cerebellar peduncle
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27
Q

Describe what the rubrospinal tract is, and outline its descending pathway

A

(flexor-biased tract) - innervates all flexor muscles of the upper limb (‘grabbing’ behaviour)
- Originates: red nucleus
- Decussates: near origin at midbrain level
- Descends contralaterally and accompanies the lateral corticospinal tract
- Passes through later column (funiculus) of the spinal cord and ends at the level of cervical cord

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28
Q

Describe the function of the tectospinal tract, and outline its descending pathway

A

Controls reflex movements of the head, neck and upper limbs in response to all relevant sensory stimuli
- cell bodies are located in the superior colliculi
- fibres cross in midbrain to contralateral
- terminate at motor neurons in cervical spinal cord
- a small potion of tectospinal tract remains ipsilateral to inhibit the muscles on one side while the contralateral muscles are excited (important for reflex) - thus acts bilaterally

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29
Q

Describe the functions of the vestibulospinal tracts, with respect to its different tracts

A
  • neurons of the medial and lateral vestibular nuclei of the medulla ONLY contribute to vestibulospinal tracts (all though there are four vestibular nuclei)
    Lateral: generates muscle tone in deep back and limb extensors - maintain stance and balance
    Medial: stabilises the head during movement (vestibulocervical reflex)
30
Q

Describe what the reticulospinal tract does, and outline its descending pathway

A

(extensor-biased tract)
- Serves postural and gait adjustments (balance) during movement by acting on anti-gravity muscles
- central for bilateral and coordinated gross movements of the limbs
- gross movements during reaching

Pathway:
- cell bodies are located in the medial column of the caudal pontine and rostral medullary reticular formation
- descends ipsilaterally and bilaterally to ventral funiculus (all levels of spinal cord)

31
Q

What is the reticular system?

A
  • a key player in brainstem function
  • comprises a set of interconnected nuclei found within the tegmentum of the brainstem
    Major subsystems:
  • ascending reticular activating system (regulates cortical arousal, consciousness and sleep, and pain arousal)
  • descending premotor tracts
32
Q

What kinds of motor activity does the reticular system control?

A
  • maintains tone and balance (via reticulospinal tracts)
  • cardiovascular control
  • control of respiration (via pontine pneumotaxic centre and the medullary respiration centre)
    -swallowing
33
Q

How does the reticular system regulate swallowing?

A

(Involuntary phase):
- sensory projections from the posterior palate to the reticular formation initiate the involuntary phase
- the reticular formation integrates the sensorimotor functions of the trigeminal, facial, glossopharyngeal, vagus and hypoglossal nerves

34
Q

Discuss some features of the basal ganglia nuclei

A
  • do not maintain direct connections with the spinal cord (input or output)
  • have an input into extrapyramidal pathways
  • work closely with supplementary motor cortex rather than premotor cortex
  • by actingg\ on supplementary cortex, basal ganglia indirectly modulate the function of pyramidal pathways
35
Q

List the subcortical nuclei components of the basal ganglia

A
  1. striatum (caudate nucleus + putamen)
  2. globus pallidus (ext. and int.)
  3. subthalamic nucleus
  4. substantia nigra (pars compacta and reticulata)
36
Q

What are the functions of the basal ganglia?

A
  • participate in control of voluntary movement
  • facilitate wanted motor plans and suppress unwanted motor plans)
  • modulate the functions of pyramidal and extrapyramidal pathways
  • do not have direct connects with the spinal cord (inputs or outputs)
  • receive major input from prefrontal cortex and send major output back to supplementary motor cortex via the thalamus (cortical-basal ganglia-(thalamo)cortical loop)
37
Q

Discuss the location of the different basal ganglia nuclei and the internal capsule in the telencephalon.

A
  • caudate nucleus (head and body), putamen and globus pallidus in the frontal and parietal lobes
  • caudate nucleus (tail) in temporal lobe
  • the internal capsule passes between the caudate nucleus and the putamen
38
Q

Describe the structure of the caudate nucleus

A
  • located in the lateral wall of the lateral ventricle and bulges into the ventricle
  • follows the lateral ventricle in a c-shaped course
  • is attached to the putamen with grey matter (cell) bridges
  • has a big head in frontal lobe indicating that it gets most of its input from frontal lobe (prefrontal cortex)
39
Q

Describe the structure and location of the striatum

A
  • tail of caudate is located in the temporal lobe and is small, indicating that it gets less input from this side
  • anteriorly, the tail of caudate is continuous with the amygdala (in temporal lobe)
  • ventral parts of the caudate and putamen to form the nucleus accumbens (ventral striatum)
  • nucleus accumbens related to reward
  • only the dorsal striatum is part of the basal ganglia
40
Q

What is the function of the substantia nigra?

A
  • production centre of neuromelanin
41
Q

What is the doorway to the basal ganglia, and what are the exit points of the basal ganglia?

A

Doorway: striatum
Exit point: (internal) globus pallidus and substantia nigra pars reticulata

42
Q

What do the indirect and direct pathways of the basal ganglia ultimately achieve?

A
  • smooth coordinated movements
43
Q

What does activation of the direct pathway of the basal ganglia achieve?

A
  • disinhibits the thalamocortical tract, thereby increasing thalamocortical activity to initiate and promote wanted action plan movements in accordance to cortical motor command
44
Q

What is the nature of the intrinsic connections of the direct pathway of the basal ganglia?

A
  • GABAergic and inhibitory
45
Q

What is the role of the substantia nigra pars compacta in the pathways of the basal ganglia?

A
  • another level of control/regulation
  • maintains functional equilibrium of the direct and indirect pathways
46
Q

In what ways are the two striatal output pathways affected differently by dopaminergic projection from the substantia nigra pars compacta?

A

striatal neurones:
direct pathway - D1 dopamine receptors
indirect pathway - D2 dopamine receptors expressing cholinergic interneurons

47
Q

What is the result of the substantia nigra pars compacta activating medium spiny interneurons in the striatum?

A

Boosts activity - the substantia nigra pars compacta acts to facilitate wanted motor plans by promoting disinhibition of thalamocortical neurons

48
Q

What pathological condition arises from lesions to the striatum, and what are the associated involuntary movements of this disorder? Why does this disease present in this way?

A

Huntington Chorea
- rhythmic and quick involuntary movements of the muscles in proximal extremities

Reduced activity of indirect pathway (inability to suppress unwanted movements)

49
Q

What pathological condition arises from lesions to the caudate nucleus, and what are the associated involuntary movements of this disease? Why does this disease manifest this way?

A

Parkinson’s Disease (because of dopaminergic deficiency owing to degenerative changes in substantia nigra)
- dyskinesia
- akinesia
- bradykinesia
- hypokinesia
- tremor (at rest) accompanied by akinesia and rigidity
Reduced activity of direct pathway, increased activity of indirect pathway

50
Q

What is the role of the cerebellum?

A

‘Comparator’ - facilitates real-time changes to motor plan, depending on peripheral feedback to map the original plan against actual enactment of said movement
1. regulates and coordinates motor function
2. maintenance of balance and posture

51
Q

Explain cerebellar function in greater detail, by referencing how the cerebellum achieves these functions

A
  • Evaluates disparities between intention and action: comparison considers targeted movement in relation to body position, muscle readiness, muscle tone, body equilibrium, distance and duration.
  • Adjusts the operation of motor cortex and the brain stem while a movement is in progress
  • Descending feedback (to LMN via rubro- and reticulospinal tracts) modulates muscle tone reflexes
52
Q

Discuss the location of the cerebellum

A
  • located in the posterior cranial fossa below the tentorium cerebelli
  • located on posterior part of the brainstem (posterior to pons, medulla, midbrain) and 4th ventricle
53
Q

Discuss the anatomical features of the cerebellum

A
  • external tightly packed gyri (folia and deep sulci)
  • two hemispheres separated by vermis
  • lacks commissural fibres
  • two flocculi on anterior surface
  • anterior, posterior and floccularnodule lobes
  • anterior and posterior lobes separated by primary fissure
  • posterior and flocculonodular lobes separated by posterolateral fissure
  • horizontal fissure divides cerebellum into superior and inferior halves
  • composed of out cerebellar cortex and internal white matter
  • superior and inferior medullary vela merge at the fastigium
54
Q

List and state the purpose of the 3 peduncles of the cerebellum.

A
  • superior cerebellar peduncle
  • middle cerebellar peduncle (largest input, very involved in control of voluntary movement for speech)
  • inferior cerebellar peduncle

Peduncles connect cerebellum to brainstem

55
Q

What are the connections of each of the cerebellar peduncles to the rest of the brain?

A

SCP - contains axons to/from the midbrain
MCP - contains axons from the pons
ICP - contains axons to/from the medulla

56
Q

List the four pairs of nuclei that are embedded within the white matter of the cerebellum

A
  1. dentate nuclei (located laterally)
  2. interposed nuclei (emboliform nuclei + globose nuclei) (2 globose nuclei each side)
  3. fastigial nuclei (located medially)
57
Q

List the 3 neuronal layers of the cerebellar cortex, and list their compositions, afferences and efferences.

A
  1. Molecular layer
    - comprised of parallel axons and dendrites
    - afferent: parallel fibres of the granule cells axons
    - efferent: Purkinje cells dendrites
  2. Purkinje cell layer
    - 15M Purkinje cells
    - afferent: parallel fibres of the granule cells and climbing fibre from inferior olivary nucleus
    - efferent: deep subcortical nuclei
  3. Granular cell layer
    - closely packed granule cells
    - afferent: mossy fibre
    - efferent: Purkinje cell dendrites
58
Q

What are the three major proprioceptive sensory receptors, and what information do they provide?

A
  1. muscle spindles - provide information about changes in muscle length
  2. golgi tendon organs - provide information about changes in muscle tension
  3. ruffini copuscles - present in joint capsules and provide information related to joint position
59
Q

List the afferent and efferent cerebellar connections

A
  1. All AFFERENT fibres entering the cerebellum terminate in the cerebellar cortex
  2. Colateral copies of the afferent fibres are ALWAYS given to the cerebellar nuclei
  3. ALL EFFERENT fibres that EXIT the cerebellar cortex are inhibitory axons of the cortical Purkinje neurones that mostly synapse with neurons of the cerebellar nuclei
  4. Efferent fibres that EXIT the cerebellum are mostly excitatory and originate from the cerebellar nuclei
60
Q

What sources of information are conveyed by climbing fibres to directly target the Purkinje cell layer?

A
  • spinal cord
  • reticular system
  • red nucleus
  • cerebral cortex
  • cerebellum itself
61
Q

What is the impact of the granule cells bifurcating in the molecular layer?

A
  • increased computational power, because thousands of dendritic Purkinje cells connect to thousands of granular cells
62
Q

What are the developmental classifications for the cerebellar regions?

A
  • archicerebellum (floccularnodular lobe - oldest part)
  • paleocerebellum (anterior lobe, vermis and paravermal region)
  • neocerebellum (lateral parts of the hemispheres)
63
Q

What are the functional classifications of the cerebellar regions?

A
  • vestibulocerebellum (floccularnodular lobe, fastigial nuclei)
  • spinocerebellum (anterior lobe, vermis and paravermal region, interposed nuclei and fastigeal nuclei)
  • pontocerebellum (cerebellar hemispheres; dentate nuclei) - cerebrocerebellum
64
Q

What projections does the vestibulocerebellum receive, and where does it send its feedback?

A
  • receives projections from vestibular nuclei and vestibular nerve
  • sends feedback to vestibular nuclei via the fastigial nuclei, primarily to influence the lateral and medial vestibulospinal tracts
65
Q

What are the functions of the vestibulocerebellum?

A
  1. vestibulospinal reflex: keeps the body in the centre of gravity (body equilibrium), by maintaining muscle tone and activating anti-gravity muscles
  2. vestibulocervical reflex (stabilises position of head)
  3. vestibulo-ocular reflex: stabilises gaze during head movement
66
Q

What the afferent inputs and efferent outputs of the vestibulocerebellar loop?

A

Afferent:
1. posterior spinocerebellar tract (proprioception info)
2. olivocerebellar tract (input from inferior olivary nucleus, only climbing fibre)
3. vestibulocerebellar tract (from vestibular nuclei)
Efferent:
1. cerebelloreticular tract
2. cerebelloolivary tract
3. cerebellovestibular tract

67
Q

What input does the spinocerebellum receive, and where does it send feedback to? What is the function of the spinocerebellum?

A
  • receives input from ipsilateral spinal cord (spinalcerebellum) mainly concerning unconscious proprioception
  • sends back information via the fastigial and interposed (globose and emboliform) nuclei to reticulospinal, rubrospinal and vestibulospinal tracts
  • regulates muscle tone, posture, and balance (via the medial motor pathways)
68
Q

What are the afferent inputs and efferent outputs of the spinocerebellar loop?

A

Afferent:
1. posterior spinocerebellar tract
2. olivocerebellar tract
3. vestibulocerebellar tract
Efferent:
1. cerebelloreticular tract
2. cerebroolivary tract
3. cerebellovestibular tract

69
Q

What is the significance of the inferior olive in the loops between the cerebellum and various other CNS structures?

A
  • it is a relay station to the rest of the extrapyramidal system
70
Q

What is the cerebrocerebellum? What afferent projections does it receive, and where does it project to?

A
  • coordinates fast and alternating movements by planning the movements with regard to their direction, timing and force
  • more concerned with hand movement and speech production
  • receives afferent projections primarily from contralateral most neocortex (e.g. motor cortex)
  • projects back via dentate nucleus to contralateral motor cortex via thalamus (VL) and red nucleus
71
Q

Provide a summary of how the 3 cerebellar loops regulate the descending motor pathways independent of each other

A

Cerebrocerebellar loop: plans movement, regulates timing, force, and direction of fast and alternating movements, CONTINUOUS loop with the pyramidal tract from the motor cortex (planning and initiating of voluntary and skilled movements)

Vestibulocerebellar loop: regulates balance and eye movements, CONTINUOUS loop with extrapyramidal tract from brainstem (control of posture balance and basic movements)

Spinocerebellar loop: regulates balance and movements of trunk and limbs, ONE WAY projection to extrapyramidal tracts from brainstem, also receives input form the spinal cord

72
Q

True or false: the cerebellum has direct input into spinal motor neurons?

A

False!
- the cerebellum influences spinal motor neurons indirectly through the descending motor pathways (pyramidal and extrapyramidal)

ANAT2005 (6 decks)

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