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Year 2 - Theme 2 > Motor learning and neurological syndromes > Flashcards

Motor learning and neurological syndromes Flashcards

1
Q

Simple motor pathway

A

Motor cortex of the brain -upper motorneurone-> lower motorneurone–> muscle

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2
Q

Brain structures associated with strategy(high level)

A
  • Association areas of neocortex and basal ganglia
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3
Q

Brain structures associated with tactics(middle)

A
  • Motor cortex, cerebellum
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4
Q

Brain structures associated with execution(low)

A
  • Brainstem, spinal cord
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5
Q

What are the three ventromedial motor pathways

A

1) Reticulospinal
2) Tectospinal
3) Vestibulospinal

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6
Q

Purpose of the descending motor pathways

A
  • These use sensory information about balance, body position and the visual environment to reflexively maintain balance and posture
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7
Q

What are betz cells

A
  • Betz cells (also known as pyramidal cells of Betz) are giant pyramidal cells (neurons) located within the fifth layer of the grey matter in the primary motor cortex.
  • Betz cells are upper motor neurons that send their axons down to the spinal cord via the corticospinal tract, where in humans they synapse directly with anterior horn cells, which in turn synapse directly with their target muscles.
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8
Q

Path of the rubrospinal tract in the midbrain

A
  • In the midbrain, it originates in the magnocellular red nucleus, crosses to the other side of the midbrain, and descends in the lateral part of the brainstem tegmentum
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9
Q

Path of the rubrospinal tract in the spinal cord

A
  • In the spinal cord, it travels through the lateral funiculus of the spinal cord, coursing adjacent to the lateral corticospinal tract.
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10
Q

Purpose of the rubrospinal tract

A
  • The tract is responsible for large muscle movement as well as fine motor control, and it terminates primarily in the cervical spinal cord, suggesting that it functions in upper limb but not in lower limb control.
  • It primarily facilitates flexion in the upper extremities
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11
Q

What is the vestibulospinal tract

A
  • It is a component of the extrapyramidal system and is classified as a component of the medial pathway.
  • Like other descending motor pathways, the vestibulospinal fibers of the tract relay information from nuclei to motor neurons
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12
Q

Information carried by vestibulospinal tracts

A

The vestibular nuclei receive information through the vestibulocochlear nerve about changes in the orientation of the head

The function of these motor commands is to alter muscle tone, extend, and change the position of the limbs and head with the goal of supporting posture and maintaining balance of the body and head

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13
Q

Origin of vestibulospinal tract

A
  • Originate in the vestibular nuclei of the medulla which relay sensory information from the vestibular labyrinth in the inner ear
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14
Q

Where does the medial vestibulospinal pathway project to

A
  • Medial vestibulospinal pathways projects down to the spinal cord and activates the cervical spinal circuits that control neck and back muscle guides and thus guide head movements.
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15
Q

What does the vestibulospinal tract do

A
  • It helps to keeps the eyes stable as the body is moved
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16
Q

Where does the lateral vestibulospinal cord project to

A
  • Lateral vestibulospinal projects ipsilaterally as far down as the lumbar spinal cord.
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17
Q

Purpose of the lateral vestibulospinal tract

A
  • Helps us maintain an upright and balanced posture by facilitating the extensor motor neurons of the legs
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18
Q

What is the tectospinal tract

A
  • The tectospinal tract (also known as colliculospinal tract) is a nerve tract that coordinates head and eye movements. This tract is part of the extrapyramidal system
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19
Q

Origin of the tectospinal tract

A
  • Originates in the superior colliculus in the midbrain which receives direct input from the retina
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20
Q

Where does the superior colliculus receive information from

A
  • The superior colliculus receives information from the retina and the visual cortex.
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21
Q

What is info from the superior colliculus used for

A
  • Used to construct a map of the world around us

- Allows us to direct the head and eyes to move so that the appropriate point of space is imaged on the fovea.

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22
Q

Where do the projections from the tectospinal tract decussate

A
  • The projections decussate immediately and lie close to the midline into the cervical regions of the spinal cord where they help to control the muscles of the neck, upper trunk and shoulders.
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23
Q

What is the reticulospinal tract

A
  • The reticulospinal tracts, also known as the descending or anterior reticulospinal tracts, are extrapyramidal motor tracts that descend from the reticular formation in two tracts to act on the motor neurons supplying the trunk and proximal limb flexors and extensors
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24
Q

Where does the reticulospinal tract run from

A
  • Runs from the brainstem
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25
Q

Location of the reticular formation

A
  • Is just under the cerebral aqueduct and fourth ventricle
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26
Q

What is the reticular formation

A
  • Complex meshwork of neurons
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27
Q

Descending pathways of the reticulospinal tracts

A

Descends in two separate pathways

  • Pontine(medial)
  • Medullary(lateral)
  • Both facilitate the extension of the limbs
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28
Q

Classification of descending pathways

A

Lateral - Rubrospinal, corticospinal

Ventro-medial - Reticulospinal, tectospinal, vestibulospinal

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29
Q

Purpose of tectospinal and medial vestibulospinal pathways

A
  • Control head and neck movements
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30
Q

Purpose of lateral vestibulospinal and reticulospinal pathways

A
  • Activate extensor muscles in arms and legs
31
Q

Purpose of rubrospinal pathway

A
  • Activates flexor muscles in arms
32
Q

What is decorticate posturing(coma)

A
  • Abnormal posturing in which a person is stiff with bent arms, clenched fists, and legs held out straight
  • The arms are bent in toward the body and the wrists and fingers are bent and held on the chest
33
Q

When is decorticate posturing present

A
  • Lesion above red nucleus
34
Q

What causes decorticate posturing

A
  • Lesion above red nucleus

- The rubrospinal tracts are disinhibited and therefore facilitate flexors in the upper limb

35
Q

What is decerebrate posturing(coma)

A
  • Decerebrate posture is an abnormal body posture that involves the arms and legs being held straight out, the toes being pointed downward, and the head and neck being arched backward. The muscles are tightened and held rigidly.
36
Q

What causes decerebrate posturing

A
  • The rubrospinal are disrupted and therefore the UL are extended. (lesion below red nucleus)
37
Q

Effect of damage to motor cortex and corticospinal tract on posture

A

Typical posture - some preserved upper limb flexion and lower limb extension

  • Increased tone(spasticity), brisk reflexes, extensor plantar/babinski reflex, clonus(BUT patient maintains a posture)
38
Q

What is the babinski reflex

A
  • The Babinski reflex occurs after the sole of the foot has been firmly stroked. The big toe then moves upward or toward the top surface of the foot. The other toes fan out
39
Q

Contrast between damage to motor neurons and motor tracts

A

Motor neurons -

  • Reduced tone
  • Loss of reflexes
  • Muscle wasting
40
Q

What is the corticobulbar pathway

A

The corticobulbar (or corticonuclear) tract is a two-neuron white matter motor pathway connecting the motor cortex in the cerebral cortex to the Medullary pyramids, which are part of the brainstem’s medulla oblongata (also called “bulbar”) region

41
Q

What is facial palsy

A
  • weakness or paralysis of the muscles of the face
42
Q

What is bell’s palsy

A
  • majority of facial palsy cases are idiopathic, termed Bell’s Palsy, there are a wide range of potential causes of a facial palsy

Bell’s palsy is a diagnosis of exclusion and hence all possible causes have to be excluded first prior to diagnosing Bell’s palsy.

43
Q

What do patients with bell’s palsy present with

A
  • varying severity of painless unilateral lower motor neuron (LMN) weakness of the facial muscles
44
Q

How can you clinically distinguish from a LMN cause and UMN cause of facial palsy

A
  • a patient with forehead sparing (i.e. no involvement to the occipitofrontalis muscle) will have a UMN origin to the palsy, due to the bilateral innervation of the forehead muscle).
45
Q

features of upper motor neuron lesion affecting facial nerve

A
  • Contralateral lower facial musculature paralysis
46
Q

Features of lower motor neuron lesion affecting facial nerve

A
  • Ipsilateral paralysis of both upper and lower facial musculature
47
Q

Stimulation of area 4

A
  • Elicit simple movements on the contralateral side
48
Q

Stimulation of area 6

A
  • Was involved in complex movements on either side of the body
49
Q

Innervation by premotor area(laterally)

A
  • PMA connects with the reticulospinal tracts and innervate proximal motor units
50
Q

Innervation by SMA(medially)

A
  • SMA innervate distal motor units directly
51
Q

What is the motor strip

A

The precentral gyrus, which may also be called the primary motor area or, most commonly, the motor strip is immediately anterior to the central sulcus

52
Q

How might a parasagittal meningioma present

A
  • By pressing on foot/leg area of both motor cortices, it presents as bilateral leg weakness and spasticity
53
Q

What is a proximal lesion in the brain likely to affect

A
  • Affects internal capsule

- Complete hemiparesis

54
Q

What is abulia and what can cause it

A
  • Loss or impairment of the ability to make decisions or act independently
  • Anterior cerebral artery stroke
55
Q

What type of neurons are present in area 5

A
  • Somatosensory afferents
56
Q

What type of neurons are present in area 7

A
  • Visual pathway afferents
57
Q

What can damage to the posterior parietal cortex cause

A
  • Damage results in neglect
  • Can perceive but do not attend
  • Exploratory movements
  • Eg turning object in hand
  • (Looking and feeling)
58
Q

Importance of the premotor area

A
  • Importance in control of visually guided movements

eg orientation of hand in relation to object to be grasped(prehension)

  • Damage may also cause- preservation of motor activity despite lack of success
59
Q

Where does the PMA receive input from and what is it in control of mostly

A
  • PMA receives input from the cerebellum and is involved in planning movements based on external(especially visual) cues
  • It is involved mostly in control of postural and proximal limb muscles
60
Q

What do lesions of PMA disrupt

A
  • Disrupt learned responses to visual cues
61
Q

Activation during a simple finger flexion

A
  • Only M1 activation
62
Q

Activation during a sequence of complex finger movements

A
  • M1 + SMA activation
63
Q

Activation during rehearsal of finger movements

A
  • Only SMA activation
64
Q

What is the bereitschaftspotential attributed to

A
  • Activation of the supplementary motor area
65
Q

what does the bereitschaftspotential precede

A
  • Precedes the ‘motor potential’ of the primary motor cortex(m1) by about 500-1000ms during self-initiated movements
66
Q

What does damage to wide interconnections between sensory and motor association areas cause

A
  • Apraxia
67
Q

What is apraxia

A
  • Inability to carryout purposeful movements in the absence of paralysis or paresis.
    Great difficulty in the sequencing and execution of movements.
68
Q

What is ideational(parietal apraxia)

A

unable to report the sequence

• Show me how to make a peanut butter sandwich?

69
Q

What is ideomotor(SMA) apraxia

A
  • unable to use the tool

• Show me how to hold and use a pair of scissors

70
Q

Link between sensory processing and task specific dystonias

A
  • Repeated and extended use of the hand results
  • in changes in the functional organisation of brain
  • areas related to sensory processing and motor control.
  • Can be altered by ‘sensory tricks’
  • Although the manifestation is motor, the primary
  • abnormality is likely to be disrupted sensory processing
  • probably mediated by the basal ganglia
71
Q

What is dystonia

A
  • sustained muscle contractions, usually producing
    twisting and repetitive movements or abnormal postures or positions.
    If only occurs with certain actions, said to be ‘task specific’
72
Q

Role of anterior cingulate gyrus

A
  • Emotional regulation
73
Q

Function of the basal ganglia

A
  • Positive feedback loop with the cortex to select wanted movements and deselect unwanted movements
74
Q

Function of cerebellum

A
  • Coordination of muscles in order to make smooth movements
  • Balance
  • Motor learning

Year 2 - Theme 2 (14 decks)

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