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Module 202 > T2L3 structure and function of the spinal chord > Flashcards

T2L3 structure and function of the spinal chord Flashcards

1
Q

at L1

A
  • spinal chord narrows to form conus medullaris

- terminal filum attaches to coccyx

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2
Q

the spinal chord

A
  • sits within the vertebral column for protection (in vertebral canal)
  • surrounded by meninges (dura, arachnoid, pia)
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3
Q

divisions of the spinal chord

A

c1-c8 cervical
t1-t12 thoracic
L1-L5 lumbar
s1-s5 sacral

lumbar cistern:
s4

cervical enlargement- innervation to upper limb
lumbosacral enlargement- innervation to lower limb

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4
Q

spinal nerves

A
  • connect periphery to spinal chord

- 31 pairs, each formed by a ventral and a dorsal root

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5
Q

ventral roots

A

efferent fibres

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6
Q

dorsal roots

A

afferent fibres

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7
Q

internal anatomy of sc

A

inner core = grey matter

  • h shaped
  • formed of neuronal cell bodies
  • the grey area has a ventral, dorsal and lateral horn

outer = white matter

  • myelinated axons
  • white tracts

has dorsal, lateral, ventral HORNS
also dorsal, lateral, ventral TRACTS
s9,s7

INCREASE GREY MATTER AT LEVELS THAT SUPPLY LIMBS (the cervical and lumbosacral enlargements)

generally:
dorsal horn = neurons receiving sensory input
lateral horn = preganglionic sympathetic neurons
ventral horn = motor neurons

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8
Q

dorsal horn

A

dorsal horn = neurons receiving sensory input

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9
Q

ventral horn

A

lateral horn = preganglionic sympathetic neurons

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10
Q

lateral horn

A

ventral horn = motor neurons

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11
Q

white matter organisation within sc

A
  • contains tracts
  • long ascending tracts carry afferent (Sensory) impulses to centres within the brain
  • long descending tracts carry efferent (motor) impulses from centres within the brain

the tracts cross ie left cerebral hemisphere controls right side of body

dorsal column = ascending tracts
lateral column = descending and ascending tracts
ventral column = mainly descending tracts

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12
Q

dorsal column

A

dorsal column = ascending tracts

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13
Q

lateral column

A

lateral column = descending and ascending tracts

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14
Q

ventral column

A

ventral column = mainly descending tracts

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15
Q

2 types of info carried by sensory (ascending) tracts

A

proprioceptive- info originating from inside the body eg from muscles, joints, tendons

exteroceptive- info originating from outside the body (pain, temperature, touch)

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16
Q

ascending tract anatomy

A

3 neurons in circuit:

  1. first order neuron (primary sensory)
    - enters spinal chord via dorsal root
  2. second order neuron
    - ascends spinal chord or brainstem
  3. third order neurons
    - projects to cerebral cortex

s11

17
Q

medial lemniscus pathway

A

s16

in DORSAL COLUMN

  • fine touch (from cutaneous mechanoreceptors), tactile discrimination and vibration
  • proprioception (from muscle spindles, joints, Golgi tendons), provides brain with positional information

first order neurons:
enter sc and ascend dorsal column on same side within the fasciculus gracilis (medial) and fasciculus cuneatus (lateral)

fibres ascend dorsal column uncrossed (longest neurons in body)

first order neurons synapse on second order neurons in MEDULLA

fasciculus gracilis terminates at nucelus gracilis
- info from lower limb
fasciculus cuneatus terminates in nucleus cuneatus
- info from upper limb

second order neurons:

  • cross in medulla and ascend to thalamus
  • form medial lemniscus s15

third order neurons:
- project from thalamus to somatosensory cortex

18
Q

damage to dorsal column

A

lesion on one side of sc:

  • eg multiple sclerosis
  • loss of tactile discrimination and proprioception on the same side
  • sensory ataxia (loss of coordination and balance) due to no proprioception
  • tested using rombergs test (standing with eyes closed>severe swaying)
19
Q

spinothalamic tract

A

s20

  • pain, temperature and crude touch (from nociceptors)

first order neurons:
- enter dorsal horn and form tract of Lissauer

synapse in dorsal horn to 2nd order neurons

second order neurons:

  • cross in dorsal horn at each level
  • ascend in anterolateral column to thalamus

third order neurons:
- project from thalamus to somatosensory cortex

20
Q

damage to anterolateral column

A

lesion on one side of sc:
- loss of pain, temp and crude touch on opposite side

outside compression of chord:
- loss of lower limb pain

inside grey matter tumour
- loss of upper limb first

21
Q

spinocerebellar tracts

A

unconscious muscle proprioception (eg from muscle spindles)

for smooth motor coordination

two uncrossed neurons only. four tracts

eg anterior and posterior spinocerebellar tracts
- carries proprioceptive info from trunk to lower limb

22
Q

posterior spinocerebellar tract

A

first order neurons:
- synapse in dorsal horn

second order neurons

  • ascend lateral column to cerebellum
  • very fast axons
  • cross over and then cross back (lol why tho)

lesion on one side of sc
- uncoordinated lower limb muscular activity on same side

23
Q

corticospinal tract

A

VOLUNTARY MOTOR PATHWAY

2 neurons in circuit:

  1. upper motor (premotor) neuron
    - cerebral cortex > ventral horn
  2. lower motor neuron
    - ventral horn > skeletal muscle
pyramidal tract (within corticospinal tract)
primary motor cortex>pyramids of medulla>lateral/anterior corticospinal tract

80% tracts cross (lateral corticospinal tract)
20% on same side (anterior corticospinal tract)

see  s28
in sc:
medial = trunk
anterolateral = proximal limb segments
posterolateral = distal limb segments
24
Q

upper motor neuron disease

A

degeneration of upper motor neurons

  • spastic paralysis (increase muscle tone)
  • overactive tendon reflexes
  • no muscle atrophy

if above pyramids - opposite side
if below pyramids - same side

eg after stroke

25
Q

lower motor neuron disease

A

degeneration of lmn in ventral horn

  • flaccid paralysis (no muscle tone)
  • no tendon reflexes
  • muscle atrophy

eg spinal muscular atrophy
- caused by defects in SMN1 gene

26
Q

amyotrophic lateral sclerosis

A

selectively affects upper and lower motor neurons

  • progressive muscle weakness and atrophy but intact mind
  • life span 5 years due to respiratory failure
27
Q

extrapyramidal tracts

A
  • don’t pass through pyramids
  • descending tracts form basal ganglia, cerebellum and pons

eg reticulospinal chord
- From reticular formation (pons) to spinal cord

Regulates ventral horn motor activity/reflexes

Facilitates and inhibits lower motor neurons

Important for posture and locomotion

Module 202 (49 decks)

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