Motor learning and neurological syndromes Flashcards Preview

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

Flashcards in Motor learning and neurological syndromes Deck (25)
1

Hierarchy of motor control
- Level
- Function
- Structures involved

Low: Execution
- Brainstem and spinal cord

Medium: Tactic
- Motor cortex, cerebellum

High: Strategy
- Association areas of neocortex
- Basal ganglia

2

Ventromedial pathways

Descending pathways, involuntary:
- Reticulospinal
- Tectospinal
- Vestibulospinal

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

3

Pyramidal/ corticospinal tract

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.

4

Rubrospinal tract
- Function
- Path

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

5

Vestibulospinal tract
- Function
- Path

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.

6

Tectospinal tract
- Function
- Path

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

7

Reticulospinal tract
- Function
- Path

Ventromedial descending motor pathway
- Facilitates extension of the limbs
- Locomotion and postural control

Path:
1. Originates in reticular formation of the brainstem

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

8

Decorticate posturing in coma

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]

9

Decerebrate posturing in coma
- Description
- Pathophysiology

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

10

Stroke and posture

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

11

Babinski reflex

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

12

Brisk reflex

Spasticity caused by a loss of descending inhibition
- Spinal inhibitory interneurones have been altered
- Increased tone

13

Corticobulbar pathway

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

14

Facial palsy and Bell's palsy

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

15

Parasagittal meningioma

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

16

Middle cerebral occlusion and its effects

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

Anterior cerebral artery stroke

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

Jacksonian mark

Partial seizure
- Associated with lesion close/ in motor cortex
- Progression starting distally from hands to legs.

19

Posterior parietal cortex

Contains:
- Somatosensory afferent paths [area 5]
- Visual afferent paths [area 7]

Function:
- Body and environmental image
- Exploratory movements
- Lesion causes neglect

20

Premotor area

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

Supplementary motor area function

Involved in mental rehearsal of movement

22

Bereithschaftspotential

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

Apraxia

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

Task specific dystonia

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

Anterior cingulate gyrus
and stroke

Connects to facial nerve
- In stoke- causes smiling when something is amusing despite not voluntarily moving it