The Motor System 3

Question 1

What is the extrapyramidal system?

Answer 1

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

Question 2

Where are the UMN cell bodies?

Answer 2

Cell bodies in central brain nuclei (deep grey matter, rather than cortex)

Question 3

Where do the extra-pyramidal axons go?

Answer 3

Do not have simple linear descending pathway

Axons form complex networks to control LMNs (and organise function)= circuits and loops

Question 4

Why is the extrapyramidal system necessary?

Answer 4

Pyramidal= lateralised, linear individual movements
Extra= groups of muscles, bilateral, choreographed/ sequenced movements so actions

Question 5

What are the structural elements of the extrapyramidal system?

Answer 5

• Basal ganglia
• Certain brain stem nuclei
• Associated connections and tracts (complex)

Question 6

What structures do the basal ganglia include?

Answer 6

• Corpus striatum (striated body)
• Substantia Nigra (black substance)
• Subthalamic nucleus

Question 7

What is the corpus striatum?

Answer 7

A complex of nuclei in the brain so striated appearance

Question 8

What does the corpus striatum consist of?

Answer 8

-Caudate nucleus
-Lenticular nucleus (lens like)
=Globus Pallidus
=Putamen

Question 9

What is the functional grouping of the corpus striatum?

Answer 9

• Caudate nucleus and putamen (neostriatum)

- Globus pallidus

Question 10

What is the substantia nigra?

Answer 10

A distinct pigmented nucleus in the midbrain

Idiopathic Parkinson’s disease affect pigmentation

Question 11

What is the subthalamic nucleus?

Answer 11

A distinct nucleus beneath the thalamus

Question 12

Which are the brain stem nuclei that are included in the extrapyramidal system?

Answer 12

• 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)

Question 13

Describe connections within the extrapyramidal system

Answer 13

• Interconnections within itself

- Connections with other things such as the thalamus, cerebral cortex, cerebellum (fine coordination system), LMN

Question 14

What does the basal ganglia influence?

Answer 14

Premotor Cortex

Supplementary Motor Area

Question 15

What are the tracts from the brain stem nuclei that descend through the spinal cord?

Answer 15

• Rubrospinal tract (red nucleus)
• Vestibulospinal (vestibular)
• Reticulospinal (reticular formation)
• Tectospinal (collicular area)

Question 16

What different transmitters are used in the circuits of the extrapyramidal system?

Answer 16

• Dopamine
• GABA
• Glutamate
• Acetylcholine

Question 17

Where are the inputs and outputs of the extrapyramidal system?

Answer 17

• 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

Question 18

What is a clinically important loop in the extrapyramidal system?

Answer 18

• Striatum- substantia nigra-striatum

- Degenerates in Parkinson’s Disease

Question 19

What are the functions of the extrapyramidal system?

Answer 19

• 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

Question 20

Describe walking

Answer 20

• 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

Question 21

What happens in extrapyramidal disease?

Answer 21

Not weakness- disruption of coordinated acts

• Abnormal motor control
• Alterations in muscular tone
• Abnormal involuntary movements

Question 22

What is abnormal motor control called?

Answer 22

-Bradykinesia, akinesia

Question 23

What are the symptoms/ signs of abnormal motor control?

Answer 23

• 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

Question 24

How does postural abnormality present?

Answer 24

• Flexed posture

- Postural instability

Question 25

How does alteration in muscular tone present?

Answer 25

-Rigidity =Lead-pipe (smooth constant resistance to movement) =Cog-wheel (cogging effect on top of background hypertonia)

Question 26

How does abnormal involuntary movements present?

Answer 26

- 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

Question 27

What are the key presentations of Parkinsonism?

Answer 27

- Bradykinesia - Rigidity - Tremor - Postural instability