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Brain And Behaviour > Descending Motor Tracts > Flashcards

Descending Motor Tracts Flashcards

1
Q

Name the pyramidal tracts

A

Corticospinal

Corticobulbar

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2
Q

Name the extrapyramimdal

A

Vestibulospinal
Reticulospinal
Tectospinal
Rubrospinal

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3
Q

Briefly what is the function of the vesitubulospinal tract?

A

Balance reflexes

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4
Q

Briefly what is the function of the tectospinal tract?

A

Eye-body coordination

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5
Q

Breifly what is the function of the reticulospinal tract?

A

Medullary (lateral) = flexor reflex facilitation and extensor reflex inhibition
Pontine (Medial) = extensor reflex facilitation

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6
Q

Functions of the corticospinal tract?

A
  1. Descending control of afferent inputs
  2. Selection, gating and gain control of spinal reflexes
  3. Excitation and inhibition of motor neurons
  4. Autonomic control
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7
Q

What are the inputs to the corticospinal tract?

A

30% SMA
30% M1
~40% S1

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8
Q

What do inputs from S1 to the CST do?

A

Descending modulation of inputs from priopceptors generated by moving. Fibres from S1 in the CST terminate on the dorsal horn and filters irreverent sensory signals

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9
Q

Where does decussation of the CST occur?

A

~85% in caudal medulla

The rest decussate on the spinal level of the motor neuron they innervate

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10
Q

What does the 85% that decussate form?

A

The lateral CST

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11
Q

What does the 15% which remain ipsilateral form?

A

The ventral CST

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12
Q

What does the CST pass through in the brain?

A

The internal capsule?
Genu of IC = face
Going outwards = arms, trunk , legs

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13
Q

What do neurons on the CST synapse on?

A

Directly to alpha

To alpha via interneurons

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14
Q

What does the lateral corticospinal tract innervate?

A

Distal musculature

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15
Q

What do neurons of the ventral corticospinal tract innervate?

A

Musculature of the pelvic and pectoral girdle

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16
Q

Where does the corticobulbar tract originate?

A

M1 - the face region of the motor homunculus

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17
Q

What does the corticobulbar tract innervate?

A

cranial nerves which contain motor nuclei for general somatic efferents and special visceral efferents motor components. This is mostly bilateral i.e. A motor nuclei will receive bilateral innervation

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18
Q

What cranial nerves have a motor modality to them?

A 
occulomotor 
Trochlear
Trigeminal
Abducens 
Facial
Glossopharyngeal
Vagus
Spinal accessory
hypoglossal
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19
Q

What muscle groups are innervated by the corticobulbar tract?

A 
Muscles of facial expression
Tounge
Extraoccular
Vocal cords
Mastication
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20
Q

What CN nuclei are not bilaterally innervated?

A

The motor nuclei for the muscle of facial expression of the lower face (why an UMN causes contralateral face paralysis but is forehead sparing)
The hypoglossal nerve motor nuclei 9UMN points tongue to contralateral side, LMN points it towards side of lesion)

21
Q

Which extrapyramidal tracts do not decussate?

A

Vestibulospinal

Recticospinal

22
Q

Which extrapyramidal tracts do decussate immediately/

A

Rubrospinal

Tectospinal

23
Q

Where does the reticospinal tract originate/

A

Pontine (medial) in the nucleus reticularis pontis oralis and caudalis
Medullary (lateral) in the nucleus reticularis giantocellularis

24
Q

The pontine (medial) reticulospinal tract does what?

A

Extensor reflex facilliatation and synapses on alpha and gamma MN to increase muscle tone

25
Q

The medullary (lateral) reticospinal tract does what?

A

Flexor reflex facilitation and extensor reflex inhibition

26
Q

What are the inputs to the vesiculospinal tract?

A

The balance organs of the vestibular apparatus and cerebellum

27
Q

Wat does the vestibulospinal tract orginate from?

A

Medial and lateral vestibular nuclei

28
Q

Where does the vestibulospinal tract terminate?

A

Interneurons which synapse to muscle of balance and posture

29
Q

What does the medial VST control?

A

Muscles of the neck e.g. Spinal accessory nerve to cause rotation and uplifting of head and neck (stabilise neck and head when walking)

30
Q

What does the lateral VST control?

A

Innervate extensor antigravity muscles. Alpha and gamma MN of lower limb muscles important for posture and balance

31
Q

Where does the tectospinal tract orginate?

A

The superior collicus within the tectum

32
Q

Where does the tectospinal tract decussate?

A

The midbrain at the ventral tegmental decussation

33
Q

Where does the tectospinal tract terminate?

A

Neurons within the upper cervical spine

34
Q

What is the function of the tectospinal tract?

A

Coordinates head movements towards visual stimuli

35
Q

How is the red nucleus organised?

A

Somatotopically

36
Q

What inputs into the red nucleus?

A

Input from M1 and premotor cortex

37
Q

Where does the rubrospinal tract decussate?

A

The ventral tegmental area

38
Q

Where does the RubroST terminate?

A

In higher animals within the C spine

In lower animals within the lumbar spine

39
Q

Why is the rubrospinal tract a ‘parallel’ system to the CST?

A

Both receive inputs from the cortex
Both somatotopically organised
Both mainly facilitate flexors

40
Q

What is the difference between positive and negative signs?

A 
\+ = emergence of feature
- = loss of function
41
Q

Name some lower motor neuron signs?

A 
Flaccid paralysis
Hypotonia
Hyporeflexia
Muscle weakness
Fasiculuations
Denervation atrophy
42
Q

Why do you get fasiculuations?

A

Increase sensitivity to Ach at NMJ so that single muscle fibres spontaneously contract

43
Q

Why do you get denervation atrophy?

A

Loss of trophies factors from presynaptic neuron in the NMJ

44
Q

Causes of LMN signs

A

MND
Diabetic neuropathy
Trauma (e.g. Laceration of the median nerve)

45
Q

What are some UMN signs?

A 
Hypertonia
Hyperreflexia
Clonus
\+ babinski sign
Disuse atrophy
Spastic hemiplegia
Clasp knife rigidity
Pronator drift
46
Q

Why do you get spastic hemiplegia?

A

There is an increase in tone of agonist and antagonist across a joint

47
Q

What is clasp knife rigidity?

A

Increase in stretch reflex = increase in tone
Tone continues to increase until eventually gives way
Dependant on how fast a limb is moved (the fast moved the more pronounced)

48
Q

Function of rubrospinal and rubrobulbar

A

distal flexor muscle tone

Brain And Behaviour (12 decks)

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