The Motor System 3 Flashcards
What is the extrapyramidal system?
All the motor centres and tracts that have a significant influence on lower motor neurones additional to the corticospinal and corticobulbar system
- Critical role in organisation of individual movements into whole actions
- Modifies and organises movements controlled by corticospinal and corticobulbar systems
Where are the UMN cell bodies?
Cell bodies in central brain nuclei (deep grey matter, rather than cortex)
Where do the extra-pyramidal axons go?
Do not have simple linear descending pathway
Axons form complex networks to control LMNs (and organise function)= circuits and loops
Why is the extrapyramidal system necessary?
Pyramidal= lateralised, linear individual movements Extra= groups of muscles, bilateral, choreographed/ sequenced movements so actions
What are the structural elements of the extrapyramidal system?
- Basal ganglia
- Certain brain stem nuclei
- Associated connections and tracts (complex)
What structures do the basal ganglia include?
- Corpus striatum (striated body)
- Substantia Nigra (black substance)
- Subthalamic nucleus
What is the corpus striatum?
A complex of nuclei in the brain so striated appearance
What does the corpus striatum consist of?
-Caudate nucleus
-Lenticular nucleus (lens like)
=Globus Pallidus
=Putamen
What is the functional grouping of the corpus striatum?
- Caudate nucleus and putamen (neostriatum)
- Globus pallidus
What is the substantia nigra?
A distinct pigmented nucleus in the midbrain
Idiopathic Parkinson’s disease affect pigmentation
What is the subthalamic nucleus?
A distinct nucleus beneath the thalamus
Which are the brain stem nuclei that are included in the extrapyramidal system?
- Red nucleus
- Reticular Formation
- Vestibular nuclei (process information of where body is in space)
- Olive (inferior olivary complex, indirectly affects LMN)
- Superior Colliculus (eye movements)
Describe connections within the extrapyramidal system
- Interconnections within itself
- Connections with other things such as the thalamus, cerebral cortex, cerebellum (fine coordination system), LMN
What does the basal ganglia influence?
Premotor Cortex
Supplementary Motor Area
What are the tracts from the brain stem nuclei that descend through the spinal cord?
- Rubrospinal tract (red nucleus)
- Vestibulospinal (vestibular)
- Reticulospinal (reticular formation)
- Tectospinal (collicular area)
What different transmitters are used in the circuits of the extrapyramidal system?
- Dopamine
- GABA
- Glutamate
- Acetylcholine
Where are the inputs and outputs of the extrapyramidal system?
- Neostriatum= input (information goes in)
- Cerebral cortex, thalamus and substantia nigra input into the EPS
- Globus pallidus and substantia nigra (interconnections with itself)= outputs
- Subthalamic nucleus, thalamus and motor cortex receive the outputs
What is a clinically important loop in the extrapyramidal system?
- Striatum- substantia nigra-striatum
- Degenerates in Parkinson’s Disease
What are the functions of the extrapyramidal system?
- Grosser, more automatic voluntary movements (walking)
- Emotional expression movements
- Bilateral control of voluntary
- Postural adjustments of body
- The continual postural adjustments that underlie smooth and coordinated voluntary movements
- Control of tone in muscles
Describe walking
- Coordinated sequence of actions
- Agonist/ antagonist groups in a leg
- Alternating actions of legs
- Involvement of paraspinal muscles (back organised and balance correct)
- Involvement of arms (swing for momentum and balance)
- Bilateral movements
What happens in extrapyramidal disease?
Not weakness- disruption of coordinated acts
- Abnormal motor control
- Alterations in muscular tone
- Abnormal involuntary movements
What is abnormal motor control called?
-Bradykinesia, akinesia
What are the symptoms/ signs of abnormal motor control?
- Slowness or poverty of movement
- Impairment of initiation, sequencing and cessation of movement
- Impairment/ loss of whole actions
- Impairment of ‘automatic’ or emotionally related movements
How does postural abnormality present?
- Flexed posture
- Postural instability
How does alteration in muscular tone present?
-Rigidity
=Lead-pipe (smooth constant resistance to movement)
=Cog-wheel (cogging effect on top of background hypertonia)
How does abnormal involuntary movements present?
- Tremor (alternating rhythmic oscillation of the body around a joint)
- Ballismus (flailing, ballistic, undesired movements of the limbs, proximal parts of limbs)
- Chorea (A type of dyskinesia characterized by rapid, jerky involuntary body movements)
- Athetosis (slow, involuntary, convoluted, writhing movements of the fingers, hands, toes, and feet and in some cases, arms, legs, neck and tongue)
- Dystonia (Unintentional sustained muscle contractions leading to abnormal postures)
- Myoclonus (sudden jerking movements)
- Tics
What are the key presentations of Parkinsonism?
- Bradykinesia
- Rigidity
- Tremor
- Postural instability
