Neuro 9 - Motor Pathways: Cortical Motor Function

Question 1

What is a volition?

Answer 1

motor systems produce movements that are adaptive and accomplish a certain goal

Question 2

Describe the hierarchical organisation of motor control.

Answer 2

Association cortex
Motor cortex
Brainstem
Spinal cord

Question 3

What are postural adjustments and unconscious processing?

Answer 3

Postural adjustments - motor system compensates for changes in the bodys centre of mass

Unconscious processing - many of the adjustments occur without our awareness

Question 4

What are the three parts of the motor cortex?

Answer 4

Primary motor cortex
Premotor cortex
Supplementary motor area

Question 5

What makes up the association cortex?

Answer 5

Frontal cortex, parietal cortex

Question 6

What are the two parts of the pyramidal system?

Answer 6

Corticospinal - innervates muscles in arms and legs

Corticobulbar - innervates muscles in the face

Question 7

Describe the side loops of this descending pathway and their role.

Answer 7

descending pathway has 2 side loops that go to the cerebellum and basal ganglia

these check the information before it goes to the muscles

Question 8

Which lobe are the three parts of the motor cortex found in?

Answer 8

Frontal

primary motor cortex = precentral gyrus

premotor and supplementary are found anterior to the primary

Question 9

What is another name given to the three parts of the motor cortex?

Answer 9

Primary motor cortex = Broadmann’s Area 4

Premotor + supplementary = Area 6

Question 10

What is the name of the most important cells in the motor cortex?

Answer 10

Betz cells

Question 11

Where are betz cells located in the grey matter and which tracts originate there?

Answer 11

5th layer of the grey matter

the corticospinal tracts originate here

Question 12

Describe what happens to the upper motor neurones that come from the primary motor cortex?

Answer 12

travel through the brainstem to the pyramidal decussation where 90% of the axons cross the midline

Travel down the spinal cord and synapse with the lower motor neurone and exit into a peripheral nerve to reach the skeletal muscle

Question 13

What are the two types of descending pathways?

Answer 13

Lateral and medial

Question 14

Which tract is in the lateral corticospinal tract?

Answer 14

lateral corticospinal tract

Question 15

What is the function of the lateral pathway?

Answer 15

control of proximal and distal musculature

voluntary movements of arms and legs

Question 16

What is the function of the anterior corticospinal tract?

Answer 16

control of axial muscles

Question 17

Describe the structure and function of the lateral corticospinal tract.

Answer 17

Originates in the primary motor cortex from the Betz cells

Travel down the brainstem and decussate at the pyramidal decussation in the medulla

Goes down the spinal cord and synapses with a lower motor neurone

Question 18

Describe the structure and function of the anterior corticospinal tract?

Answer 18

Made up of the upper motor neuron axons from the primary motor cortex that do not decussate at the pyramidal decussation at the medulla

cross the midline at the level of the spinal cord

Question 19

What diagram depicts the somatotopic organisation of the primary motor cortex?

Answer 19

Penfield’s motor homunculus

Question 20

How can the cortical representation of a muscle in the motor cortex change?

Answer 20

the more we use a muscle, the bigger the representation of that muscle in the cortex

Question 21

What is the function of the premotor cortex?

Answer 21

Plans movements and assembles movements into coordinated actions

Question 22

What is the function of the supplementary motor area?

Answer 22

planning complex internally driven voluntary movements

Question 23

What are the two parts of the association cortex that are involved in motor control?

Answer 23

Posterior parietal cortex - ensures movements are targeted accurately to objects in external space

Prefrontal Cortex - involved in the selection of appropriate movements for a particular course of action

Question 24

Describe the features of upper motor neurone lesions?

Answer 24

1) loss of function - paresis, paralysis

2) regain of spastic - spasticity, hyperreflexia, clonus

Question 25

What is Babinki’s sign?

Answer 25

stroke the plantar surface of the foot and in normal you will see flexion of the toes

UML = extensor plantar response

Question 26

Why is muscle atrophy not seen in UPL?

Answer 26

Lower motor neurones are in tact so still provide nutrients to muscles

Question 27

Define apraxia.

Answer 27

Disorder of skills movement not caused by weakness

Question 28

Lesions in which part of the brain will cause apraxia?

Answer 28

Frontal lobe - premotor and supplementary

Question 29

What are the two most common causes of apraxia?

Answer 29

Stroke, dementia

Question 30

Describe the features of lower motor neurone lesions?

Answer 30

Hypotonia
hyporreflexia
weakness
muscle atrophy
fasciculations
fibrillations

Question 31

What is motor neurone disease?

Answer 31

progressive neurodegenerative disorder of the motor system

can affect lower, upper or both

Question 32

What is the term given to upper and lower motor neurone disease?

Answer 32

ALS

Question 33

Describe how the symptoms of ALS change as the disease progresses?

Answer 33

may present with only upper/lower but both will eventually come

Question 34

List some signs of ALS?

Answer 34

• Increased muscle tone
• hyperreflexia
• babinski’s sign
• dysphagia

Question 35

Which lower motor neurone controls the tongue?

Answer 35

Hypoglossal

Question 36

What might you see in the tongue of an MND patient?

Answer 36

Fasciculations and spasticity