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Sc 24 Healthy Nervous System > L7 Spinal cord and ascending pathways of the Nervous System > Flashcards

L7 Spinal cord and ascending pathways of the Nervous System Flashcards

1
Q

Segments of the Spine

Vertebrae

A

8 cervical

12 thoraci

5 lumbar

5 sacral

1 coccygeal

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2
Q

End of spinal cord

A

L1/2

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3
Q

Enlargements of the Spinal cord

A

Cervical enlargement: around C6

Lumbar enlargement: around L3

Ventral horns are enlarged at these points, due to limb muscles being supplied near here.

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4
Q

Sensory informations

enters via:

A

Dorsal horn

Dorsal root ganglion - contains primary sensory neuron cell bodies

- carries sensory information into the CNS

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5
Q

Motor information

Goes out via:

A

Ventral Horns

Motor neurones loacated here

enlarged at cervical and lumbar regions due to many limb muscles to innervate

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6
Q

Organisation of WHITE/GREY matter in CNS

A

Grey Matter:

  • inside in CNS (outside in brain)
  • cell bodies

White Matter:

  • Outside in CNS (inside in Brain)
  • Myelinated Axons
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7
Q

CSF

(Dura & Arachnoid are stuck together)

Dura - toughest

Arachnoid - spider web like

A

CSF: found in the sub-arachnoid space

  • In between the Pia Mater & Arachnoid Mater

Lumbar puncture :

CSF removed around the Cauda Equina area

usually done in L3/4 or L4/5

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8
Q

Proprioception

A

Unconscious preception of movement and spatial orientation arising from stimuli within the body

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9
Q

Nociception

A

Neural process of encoding & processing noxious stimuli.

Afferent activity produced in peripheral & CNS by stimuli that have potential to damage tissue

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10
Q

Ascending Pathways

3 main ones (1 alternative slower pathway)

A
  1. Dorsal Column-medial Lemniscus Pathway
  2. Spinothalamic Pathway
    1. (Spino-reticulothalamic pathway: alternative)
  3. Spinocerebellar pathways
    • dorsal
    • ventral
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11
Q

Dorsal column-medial lemniscus Pathway

A
  • Fine discriminative touch
  • Vibration
  • Proprioception (V IMP!!)

All using Mechancoreceptors as their modality

Gracile Fasciculus (medial area)

  • exits below level of T6 as well as above

Cuneate Fasciculus (more lateral)

  • ONLY above T6; joins with the Gracile Fasciculus
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12
Q

Spinothalamic Pathway

Fast; has few synapses

A
  • Pain (“fast” pain) - nocioceptors
  • Temperature - thermoreceptors
  • Crude touch - mechanoreceptors

N.B. Pain and Temperature are the two main ones here, crude touch to a lesser extent

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13
Q

(Spino-reticulothalamic Pathway)

A
  • Evolutionarily “older”
  • “slow” dull aching pain
    • many synapses
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14
Q

Spinocerebellar Pathways

  • Dorsal
  • Ventral

2 of these and they lie on the lateral aspects of the spinal cord

A
  • Proprioception
  • Touch

N.B: spinocerebellar pathways are important on putting sensory information together with vestibular information i.e. posture and balance etc

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15
Q

Ascending Pathway

A

Direction if Information Flow:

Skin -> 1st order ->2nd order ->3rd order->Cortex

1st order:

  • 2 axons; considered as one axon which branches
  • Cell body: in Dorsal Root Ganglion
  • goes into Dorsal Horn

Somatosensory Cortex: interprets sensory information

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16
Q

Dorsal Column-Medial Pathway:

  • discriminative touch, proprioception, vibration sense

contralateral pathway! Info from one side of the body is recieved by the other side of the brain

A

1st order neurones:

  • Gracile tract: enter below level of T6; travel up the Fasciculus Gracilis (medially)
  • Cuneate Tract: enter above level of T6; travel up the Fasciculus Cuneatus (lateral to the Fasciculus Gracilis which it travels with)

Synapses and then dessucate at the Cuneate and Gracile Nuclei (in the dorsal medulla at the bottom of the 4th ventricle) where the cell bodies of the 2nd order neurones lie

2nd order neurones:

  • Travel up the Medial Lemniscus pathway into the Thalamus where they synapse with the 3rd order neurones

3rd order neurones:

  • Travel up through the Internal Capsule to the Somatosensory Cortex
17
Q

INTERNAL CAPUSLE

A
  • where huge motorway of axons that go up and down lie
  • primary stroke site:
    • ​area served by extremely small vessels
    • can easily be an embolism or haemorrhage at this site
18
Q

Spinothalamic Pathway

  • Pain; temperature; crude touch

contralateral pathway! Info from one side of the body is recieved by the other side of the brain

A

1st order neurones:

  • ​Synapses immediately in the spinal cord

2nd order neurone

  • Axon crosses the midline
  • Done at a slight slope; therefore a lesion here would probably produce a defect a few spinal segments BELOW the lesion
  • Travels up to the Thalamus (VPL) in the Spinothalamic Tract

3rd order neurone:

  • travels from the VPL up to the Somatosensory cortex via the Internal Capsule
19
Q

Spinothalamic verus Spino-reticulo-thalamic Pathway

A

Spinothalamic:

  • A-delta mechanical nociceptors; small myelinated fibres
  • Terminates in the VPL of the Thalamus
  • Cortical Terminations in S1
  • Functions to localise sharp “fast” pain

Spino-reticulo-thalamic pathway:

  • C-polymodal nociceptors; unmyelinated nerve fibres
  • Terminates in medial thalamus and hypothalamus
  • Cortical terminations in frontal lobe and limbic lobe
  • Functions in cortical arousal and affect
20
Q

Somatosensory Cortex

A

behind central sulcus

destination for sensory information

21
Q

Homunculus

Somatosensory

A

Representation of the body in the somatosensory cortex

Amount of sensory information from different body regions varies, hence the representation is not anatomically proportional.

Body map represents the amount of sensory information relayed back to the somatosensory cortex

22
Q

Effects of Lesion to Dorsal Columns

A
  • loss of fine touch, proprioception and vibration sense
  • location: below the lesion ipsilaterally
    • ​since the axons come straight up
23
Q

Effects of lesion to Medial Lemniscus in the Brainstem

A
  • Location: below the lesion contralaterally*
  • this crosses the midline*

same as dorsal column, loss of fine touch, proprioception and fine touch

24
Q

Effect of Lesion to SPinothalamic Tract

A

Loss of crude touch, pain and temperature sense

Location: several spinal segments below the lesion (since it crosses the spinal cord at a slope) CONTRALATERALLY

2nd order neurons cross the midline to go up

25
Q

Clinical lesions: Dorsal Columns

A

Tabes dorsalis:

  • late manifestation of Tertiary syphilis - degeneration of dorsal spinal roots & dorsal columns
  • Loss of proprioception - high step, unsteady gait - sensory ataxia
  • Romberg’s sign - worse with eyes shut; can fall over backwards (sensory ataxia - can’t make the small movements to stay upright)

Subacute combined degeneration of the cord :

  • B12 - cyanocobalamin deficiency- pernicious anaemia
  • Degeneration of dorsal columns. Also lateral columns (“combined ” ) - weakness and spasticity of limbs

Multiple sclerosis:

  • Many effects in CNS
  • Fasciculus cuneatus - loss of prioception in hands and fingers
  • Loss of dexterity; inability to identify shape & nature of objects - astereognosis
26
Q

Clinical Lesions:

Spinothalamic Tract

A

Syringomyelia:

  • Central canal enlarged by gelatinous syrinx
  • Decussating 2nd order pain/temperature neurons anteriorly compressed
  • Dissociated cutaneous loss of pain and temperature – light touch preserved

Cordotomy /tractotomy:

  • Elective surgical lesion of tracts for the relief of intractable pain
27
Q

Clinical lesions - Spinocerebella System

A

N.B. Cerebellum acts as a comparator between incoming information spinocerebellar, vestibulocerebellar and corticocerebellar systems to refine motor programmes

Cerebellar damage:

Ataxia; incoordination; intention tremor

Ipsilateral effect

Friedreich’s ataxia:

Inherited degeneration of system; congenital disorder

28
Q

Brown Sequard Syndrome

A

hemisection of the spinal cord

leads to:

  • ipsilateral spastic paralysis below the lesion
  • ipsilateral loss of fine touch, proprioception, vibration below the lesion
  • contralateral loss of pain and temperature sense several segments below the lesion
29
Q

Syringomyelia

A

tubelike enlargement of spinal canal – usually cervical/thoracic

leads to -

  • ipsilateral flaccid paralysis if ventral horns are affected – weakness and atrophy of hand muscles
  • spinothalamic tract may be first affected due to proximity of crossing fibres to central canal – loss of pain and temperature sense bliaterally in arms and shoulders

Sc 24 Healthy Nervous System (9 decks)

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