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202: Theme 2, Sensory inputs and motor outputs > Motor learning and neurological syndromes > Flashcards

Motor learning and neurological syndromes Flashcards

1
Q

Hierarchy of motor control

  • Level
  • Function
  • Structures involved
A

Low: Execution
- Brainstem and spinal cord

Medium: Tactic
- Motor cortex, cerebellum

High: Strategy

  • Association areas of neocortex
  • Basal ganglia
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2
Q

Ventromedial pathways

A

Descending pathways, involuntary:

  • Reticulospinal
  • Tectospinal
  • Vestibulospinal

Uses sensory information about balance, body position and vision
- Maintains balance and posture

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3
Q

Pyramidal/ corticospinal tract

A

Lateral descending motor pathway

  • Initiates at the motor cortex
  • Brodman areas 4 +6
  • Cells are mainly from layer V [Betz cells]

Travels through internal capsule and cerebral peduncle

90% of the fibres cross in lateral tract, the rest are ipsilateral in anterior tract.

Fibres synapse directly onto motor neurones.

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4
Q

Rubrospinal tract

  • Function
  • Path
A

Lateral descending motor pathway
- Stimulates the flexor muscles in the upper limb.

Path:

  • Initiates at red nucleus
  • Crosses at the midbrain
  • Travels down the lateral columns of the spinal cord
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5
Q

Vestibulospinal tract

  • Function
  • Path
A

Ventromedial descending motor pathway

  • Tract originates in vestibular nuclei of the medulla [medial and lateral]
  • Sensory information originates from vestibular labyrinth in the ear.

Medial vestibulospinal tract

  • Controls neck and back muscle to guide head movements
  • Keeps eyes stable as body moves

Lateral vestibulospinal [projects ipsilaterally]

  • Stimulates extensor motor neurones in the legs
  • Maintains upright and balanced posture.
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6
Q

Tectospinal tract

  • Function
  • Path
A

Ventromedial descending motor pathway

  • Controls muscles of the neck, upper trunk and shoulders.
  • Co-ordinates head and eye movements

Path:

  1. Originates in the superior colliculus of the tectum.
    - Receives visual information from retina and visual cortex.
  2. Fibres cross in the midbrain and travels down the anterior white column of the spinal cord- contralateral control
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7
Q

Reticulospinal tract

  • Function
  • Path
A

Ventromedial descending motor pathway

  • Facilitates extension of the limbs
  • Locomotion and postural control

Path:
1. Originates in reticular formation of the brainstem

  1. Descends down the spinal cord to form medial [pontine] and lateral [medullary] tract
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8
Q

Decorticate posturing in coma

A 
Stimulation from:
- Supraorbital pressure
- Nail bed
- Sternum
Causes extension of legs and flexion of arms.

Due to lesion above the red nucleus
- Rubrospinal tract intact and more active as regulation from cortex is disrupted [disinhibition]

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9
Q

Decerebrate posturing in coma

  • Description
  • Pathophysiology
A 
Stimulation from:
- Supraorbital pressure
- Nail bed
- Sternum
Causes extension in all limbs.

Mechanism:

  • Lesion below the red nucleus, rubrospinal tract is inhibited due to disruption
  • Upper limbs are extended due to activation of lateral vestibulospinal and reticulospinal tract
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10
Q

Stroke and posture

A

Stroke in middle cerebral artery can affect motor cortex and corticospinal tract

  • Lower limb extension
  • Upper limb flexion

Other features:

  • Plasticity
  • Brisk reflex [overactive reflex due to upper motor neurone lesion]
  • Babinski reflex
  • Clonus
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11
Q

Babinski reflex

A

Extension of the feet when stimulated.

  • Seen in those who have lost corticospinal tract [loss of descending inhibition]
  • Normal response is to flex feet
  • Corticospinal tract is not developed in humans until around the age od 2
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12
Q

Brisk reflex

A

Spasticity caused by a loss of descending inhibition

  • Spinal inhibitory interneurones have been altered
  • Increased tone
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13
Q

Corticobulbar pathway

A

Axons project from

  • Cingulate motor area
  • Primary motor area
  • Layer 5 of the motor neurones inn brainstem

Facilitates

  • Mastication via CN V
  • Vocal cords/ swallowing via CN IX and X
  • Tongue movements via CN XII
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14
Q

Facial palsy and Bell’s palsy

A

The top half of the face is innervated by CN 7 bilaterally
- Damage in one CN 7 can still give sensation to top half of face

Lower half of the face is contralaterally innervated
- Lesion causes loss of control on lower face

Lesion in upper motor neurone affects the entire half of the face

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15
Q

Parasagittal meningioma

A

Non benign [usually] neoplasm of the meninges
- Can press on specific areas of the motor cortex, the the one controlling the legs

Can represent as bilateral leg weakness and spasticity

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16
Q

Middle cerebral occlusion and its effects

A

Proximal lesion = complete hemiparesis
- As it affects the internal capsule, connected to the cortical area of leg motor supply

Distal lesion can allow legs to still have function
- But affect hand and face

17
Q

Anterior cerebral artery stroke

A

ACA supplies medial cortex and frontal lobe
- Includes motor control of legs

Stroke can cause:

  • Leg paresis [leg motor cortex lesion]
  • Abulia: inability to make decisions or act independently [frontal lobe lesion]
18
Q

Jacksonian mark

A

Partial seizure

  • Associated with lesion close/ in motor cortex
  • Progression starting distally from hands to legs.
19
Q

Posterior parietal cortex

A

Contains:

  • Somatosensory afferent paths [area 5]
  • Visual afferent paths [area 7]

Function:

  • Body and environmental image
  • Exploratory movements
  • Lesion causes neglect
20
Q

Premotor area

A

Structure
- Inputs from the cerebellum

Controls/ plans visually guided movements

  • Prehension [grasping and object via orientation of hand]
  • Controls postural and proximal limb muscles

Damage:

  • Perseveration of motor activity despite lack of success
  • Disrupts learned response to visual cues
21
Q

Supplementary motor area function

A

Involved in mental rehearsal of movement

22
Q

Bereithschaftspotential

A

Measured the activation of the supplementary motor area before performing an action.

This potential preceded potential from the motor cortex 500-1000ms in self-initiated movements

23
Q

Apraxia

A

The inability to carryout purposeful movements

  • In absence of paralysis or paresis
  • Inability to sequence and execute movements successfully

Ideational

  • Cannot report sequence
  • Damage to parietal

Ideomotor

  • Unable to perform action despite reporting sequence
  • damage to SMA
24
Q

Task specific dystonia

A

Repeated use of the hand can cause changes in functional organisation of the brain areas that process and execute motor control
- Causes sustained muscle contraction [twisting, abnormal posture]

25
Q

Anterior cingulate gyrus

and stroke

A

Connects to facial nerve

- In stoke- causes smiling when something is amusing despite not voluntarily moving it

202: Theme 2, Sensory inputs and motor outputs (13 decks)

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