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LCRS Neuroscience > Motor pathways > Flashcards

Motor pathways Flashcards

1
Q

What is volition?

A

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

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2
Q

What is proprioception?

A

Information on the starting point of an action, length of muscles and forces needed

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3
Q

What does functional segregation mean?

A

Motor system is organised into different areas which control different functions

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4
Q

What does hierarchical organisation mean?

A

High order areas are involved in complex functions (programme and decide on movement, coordinate muscle activity) and lower order ares carry out simple functions (execution of movement)

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5
Q

What is the motor system hierarchy?

A

Level 1: Spinal cord (basic- movement)
Level 2: Brainstem- centre of integration of different inputs coming from the vestibular system, the vision system and auditory system
Level 3: Motor cortex- primary motor cortex, premotor cortex and supplementary motor area (movements are coordinated)
Level 4: Association cortex- contains parietal and frontal cortex (involved in planning and execution of movements)

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6
Q

In terms of motor system organisation, what are the two main parts of the pyramidal (descending) system?

A

Corticobulbar tract and corticospinal tract

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7
Q

What is the corticobulbar tract?

A

Starts in cortex, then exits and innervates the muscles in the face

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8
Q

What is the corticospinal tract?

A

Starts in the cortex and innervates the muscles of the arms and legs

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9
Q

Where do the two side loops of the descending pathway go to and what happens at these locations?

A

Basal ganglia and cerebellum, information gets checked and approved

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10
Q

Which 3 parts of the motor cortex are found in the frontal lobe?

A

Primary motor cortex (M1)- Broadmann’s area 4
Premotor cortex- Broadmann’s area 6
Supplementary motor area- Broadmann’s area 6

They are anterior to the central sulcus

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11
Q

What does the central sulcus separate?

A

Frontal and parietal lobes

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12
Q

Which cells are the most important in the primary motor cortex?

A

Betz cells (pyramidal cells)

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13
Q

Why are Betz cells important?

A

Corticospinal tracts originate from them

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14
Q

What route does the corticospinal tracts follow?

A

They start in the primary motor cortex, descend and go through the brainstem all the way down. They cross over to the other side at the medulla oblongata at the pyramidal decussation. They then continue all the way down the spinal cord and synapse with a lower motor neurone and exit into a peripheral nerve to reach the skeletal muscle.

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15
Q

What route does the corticolbulbar tracts follow?

A

They start in the primary motor cortex, descend and go down into the brainstem and they synapse with a second motor neurone and send innervation to muscles of the face

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16
Q

What two groups are the descending pathways split into based on function?

A

Lateral and medial pathways

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17
Q

Which pathways are in the lateral group and what is their function?

A

Lateral corticospinal and rubrospinal

They control proximal and distal muscles
They’re involved in voluntary movements of arms and legs

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18
Q

Which pathways are in the medial group and what is their function?

A

Vestibulospinal, reticulospinal, tectospinal and anterior corticospinal tract

They control axial muscles
They’re involved in balance and posture

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19
Q

What percentage of corticospinal tract axons cross over at the pyramidal decussation and what do they form?

A

90% and they form the lateral corticospinal tract, the others are in the anterior corticospinal tract

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20
Q

Where does the rubrospinal tract originate?

A

In the red nucleus of the midbrain

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21
Q

Why is the rubrospinal tract important?

A

It is an alternative by which voluntary motor commands can be sent to the spinal cord. So if there is a lesion to the primary motor cortex, the body can still compensate and other descending tracts get activated.
It has a role in movement velocity

22
Q

What would a lesion in the rubrospinal tract cause?

A

Movements to be much slower as it has a role in movement velocity

23
Q

Where do the lateral and medial vestibulospinal tracts originate?

A

Lateral originate in the lateral vestibular nucleus (brainstem) and medial originate in the medial vestibular nucleus

24
Q

What do lateral and medial vestibulospinal tracts mediate?

A

Postural adjustments and head and eye movements

25
Q

What are tracts names based on?

A

Where they originate and where they travel- e.g. corticospinal - originate in the cortex and travel through the spinal cord

26
Q

Where do the pontine and medullary reticulospinal tracts originate?

A

Brainstem’s reticular formation

27
Q

What are the pontine and medullary reticulospinal tracts involved in?

A

Orienting, stretching and maintaining a complex posture

28
Q

Where does the tectospinal tract originate?

A

Superior colliculus

29
Q

What is the tectospinal tract involved in?

A

Unknown but most likely involved in reflexive turning of head to orient to visual stimuli

30
Q

Where does the anterior corticospinal tract originate?

A

Motor cortex

31
Q

What does the anterior corticospinal tract control?

A

Proximal musculature

32
Q

Where is the premotor cortex in relation to the primary motor cortex?

A

It is anterior to the primary motor cortex in the frontal lobe

33
Q

What does the premotor cortex do?

A

It plans movement and is involved in assembling movements into coordinated actions

34
Q

What is the function of the supplementary motor area?

A

Planning complex internally driven movements e.g. speech

Also when thinking about movement before movement

35
Q

What is association cortex?

A

Brain areas that aren’t really motor areas because their activity doesn’t correlate with motor output- they don’t have any upper motor neurones

36
Q

What are the two main components of association cortex?

A

Posterior parietal cortex and prefrontal cortex

37
Q

What does posterior parietal cortex do?

A

Ensures movements are targeted accurately to objects in external space

38
Q

What does the prefrontal cortex do?

A

It is involved in the selection of appropriate movements for a particular course of action

39
Q

What is the first effect of an upper motor neurone lesion?

A

Loss of function which leads to paresis and paralysis

40
Q

What is paresis?

A

Graded weakness of movement

41
Q

What happens in an upper motor neurone lesion after a few weeks?

A

Increased abnormal motor function- loss of inhibitory descending inputs. This results in spasticity, hyperreflexia and clonus

42
Q

What is clonus?

A

Abnormal oscillatory muscle contraction

43
Q

What is Babinski’s sign?

A

Very important sign of an upper motor lesion. If you stroke the plantar side of the foot, the toes will flex down including the big toe but after upper motor neurone lesion, toes will fan and big toe will go up

44
Q

What is apraxia?

A

A disorder in skilled movement not caused by weakness, abnormal tone or posture or movement disorders. They have lost information about how to perform skilled movements

45
Q

When does apraxia occur?

A

Lesions of the inferior parietal lobe and frontal lobe- stroke and dementia are most common causes

46
Q

What does a lower motor neurone lesion affect?

A

The second motor neurone (starts in the grey matter of spinal cord and exits to form peripheral nerve)

47
Q

What are the signs of a lower motor neurone lesion?

A

Weakness, hyporeflexia, hypotonia, muscle atrophy, fasciculations and fibrillations

48
Q

What are fasciculations?

A

When damaged motor units produce spontaneous action potentials, resulting in a visible twitch

49
Q

What are fibrillations?

A

Twitches of individual muscle fibres- aren’t visible to the naked eye but can be recorded if the patients have needle electromyography

50
Q

What is amyotrophic lateral sclerosis (ALS)?

A

Motor neurone disease that affects both upper and lower motor neurones

51
Q

Why is ALS difficult to diagnose?

A

Because it is a combination of upper and lower motor lesions which have opposite signs

LCRS Neuroscience (18 decks)

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