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Neuro > The somatosensory > Flashcards

The somatosensory Flashcards

1
Q

What motor neurons are in the brainstem?

A

Upper motor neurons

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2
Q

What is the Fritsch and Hitzig experiment?

A

Electrically stimulated the cortex (anterior)
- Elicited contraction of the contralateral body muscles
- Region is now known as the motor cortex

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3
Q

How is the motor cortex mapped?

A

Somatotopically
- Lower body is represented medially
- Upper body is mediated laterally
- The proportions reflect the density of innovation

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4
Q

What motor neurons are in the spinal cord?

A

Lower motor neurons

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5
Q

What movement do axial muscles provide?

A

Trunk movement

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6
Q

What movement do proximal muscles provide?

A

Shoulder, elbow, pelvis and knee

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7
Q

What movement do distal muscles provide?

A

Hands, feet, digits

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8
Q

What do lower motor neurons in the ventral horn innervate?

A

Striated muscle via neuromuscular junctions

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9
Q

What is the motor unit?

A

The motor neuron and all the muscle fibres it innervates

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10
Q

What is the motor neuron pool?

A

All the motor neurons that innervate a single muscle

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11
Q

How are motor pools organised?

A

Grouped in rod shaped clusters within the spinal cord extending over several vertebral segments
- Grouped together with all the motor neurons that innervate a particular muscle

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12
Q

What would allow you to trace motor neurons to the spinal cord?

A

Retrograde labelling

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13
Q

How is a motor pool organised?

A

Somatotopic
- Organisation reflects the organisation of the body
- Both medio-laterally and rostro-caudally

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14
Q

How do upper motor neurons project axons to lower motor neurons?

A

Via the descending tracts

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15
Q

What is the lateral pathway in control of voluntary movement ?

A

Corticospinal tracts

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16
Q

Where do the axons of the CST reside?

A

Layer 5 of the motor cortex

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17
Q

What are the main inputs into the motor cortex?

A

Stellate cells in layer 4

18
Q

Where are the main outputs for the motor cortex?

A

Layers 4, 5 and 6

19
Q

What are axons of the corticospinal tract derived from?

A

Large pyramidal cells

20
Q

Function of motor cortex upper motor neurons

A

Primarily concerned with fine voluntary control of distal structures

21
Q

Function of brain stem upper motor neurons

A

Project to medial motor pools
- Concerned with postural movements

22
Q

How do axons of the corticospinal tract project?

A

Cross the midline in the pyramidal decussation in the medulla
- Project laterally in the spinal cord to synapse on laterally located lower motor neurons
- Lower motor neuron circuits control distal muscles

23
Q

Where do outputs for the upper body originate?

A

From the lateral motor cortex

24
Q

Where do outputs for the lower body originate?

A

Medial motor cortex

25
Q

How do axons of the brainstem project?

A
  • Ipsilaterally in vestibulospinal and reticulospinal tracts
  • Medially in the spinal cord
  • Synapse on medially lower motor neuron circuits that control axial muscles
26
Q

What is the function of the ventromedial pathway?

A

Control posture

27
Q

How does the ventromedial pathway project?

A

Mainly ipsilaterally and medially

28
Q

Function of the vestibulospinal tract

A

Head balance and turning

29
Q

Function of the tectospinal tract

A

Orienting response

30
Q

Function of the reticulospinal tracts

A

Control antigravity reflexes

31
Q

How does the body compensate forces?

A

There is anticipatory ‘feedforward’ mechanism
- Posture is adjusted by anticipating the movement

32
Q

What is the function of premotor area 6?

A

Movement anticipation
- Activates an indirect projection to axial muscles via reticular formation

33
Q

What is the function of motor area 4?

A

Movement initiation
- Activation of voluntary movement direct to spinal cord via the corticospinal tract

34
Q

What does activity in the PMA preceed?

A

Activity in area 4 and coincides with movement planning/anticipation

35
Q

Where is the anticipation circuit?

A

From the motor cortex to the brainstem nuclei

36
Q

Describe motor neuron disease

A

Degenerative disease
- Muscular atrophy and sclerosis of the lateral spinal cord
- 3 years is a typical timecourse

37
Q

Describe lower motor neuron disease

A
  • Muscle paresis or paralysis
  • Loss of stretch reflexes
  • Severe muscle atrophy
  • Patients usually die from lung dysfunction
38
Q

Describe upper motor neuron disease

A
  • Muscle weakness
  • Spasticity due to increased muscle tone (failure of modulation of stretch reflex)
  • Hyperactive reflexes
  • Loss of fine voluntary movement
  • Patients usually die from loss of input of the bulbar muscles via the corticobulbar tract
39
Q

What causes neurons to degenerate in MND?

A
  • Excitoxicity, glutamate overstimulation causes neuronal cell death
40
Q

What drug can alleviate MND?

A

Riluzole
- Blocks glutamate release

Neuro (25 decks)

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