Excitable cells 7: Motor nervous system and diseases Flashcards

1
Q

Where are alpha-motor neurons located?

- controlled at which levels?

A

Ventral horn of spinal cord and hindbrain

  • controlled at:
  • spinal cord
  • descending pathways from upper motor neurons in brain
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2
Q

Name and describe the 2 main descending pathways of alpha motor neurons
- mention function

A

Ventromedial

  • upper MN are in brain stem
  • controls posture and locomotion

Lateral

  • upper MN are in motor cortex
  • controls voluntary movement of distal muscles
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3
Q

Describe the pathway and function of the corticospinal tract (CST)

A

Main human lateral pathway

  • motor cortex
  • thalamus
  • base of cerebral peduncle (midbrain)
  • medulla
  • pyramidal decussation
  • corticospinal tract
  • > lower motor neurone
  • > peripheral nerve
  • > muscle

Controls voluntary movement of distal muscles

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4
Q

What does the conduction block in or death of lower motor neurons result in? What diseases can cause this?

A

Results in paralysis
caused by
- Spinal muscular atrophy
- Amyotrophic Lateral Sclerosis

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5
Q

Which cells aid with cortical control of voluntary movement? Describe cells and pathway

A

Betz cells

  • huge but few in number
  • Originate in pre-central gyrus = primary motor cortex

Pathway
Betz cell ‘upper neuron’
-> pryamidal tract = corticospinal tract
-> ventral horn cell ‘lower neuron’

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6
Q

Two important pathways for cortical control of upper Motor neurons?

A

Basal ganglia:
Frontal cortex -> basal ganglia -> thalamus -> motor cortex

Cerebellum:
Multiple cortical regions -> pons -> cerebellum -> thalamus -> motor cortex

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7
Q

Example of diseases associated with

  • death of basal ganglia neurons
  • death of cerebellar neurons
A

Parkinson’s, Huntington’s disease
(death of basal ganglia neurons)
Spinocerebellar ataxias
(death of cerebellar neurons)

  • movement disorders
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8
Q

Two general types of neural lesion/dysfunction

A
  • White matter (WM)/ interrupted axonal conduction;

- Grey matter (GM)/ death of neurons (post-mitotic cells; irreplaceable)

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9
Q

Syndromes affecting either white matter and/or grey matter

A
  • Injury - penetrating or blunt, to head, spine, limb
  • Stroke - ischaemic or haemorrhagic
  • Infection – meningitis, encephalitis
  • Neural tumour – astrocytoma is most common
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10
Q

Diseases primarily affecting white matter

A
  • Multiple sclerosis – CNS inflammatory demyelination
  • Paraplegias – distal degeneration of spinal cord tracts
  • Neuropathies – distal degeneration and/or demyelination of peripheral nerve
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11
Q

Diseases primarily affecting grey matter

A
  • Motor neuron diseases – amyotrophic lateral sclerosis, spinomuscular atrophy
  • Cerebellar diseases – spinocerebellar ataxias
  • Basal ganglia diseases – Huntington’s, Parkinson’s (movement disorders)
  • Temporal/frontal lobe diseases – Alzheimer’s, frontotemporal lobe dementias
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