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OS9.1 - Neuro > Tracts > Flashcards

Tracts Flashcards

1
Q

Epicritic carries what?

A
  • fine/discriminatory touch (texture, slippage, position)
  • vibration
  • proprioception
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2
Q

Epicritic runs where?

A
  • dorsal/posterior column in spinal cord - afferents add laterally as it ascends: fasciculus cuneatus (cervical/above T6) is lateral and fasciculus gracilis (lumbar/below T6) is medial
  • synapse in dorsal nuclei in medulla (cuneatus and gracilis)
  • secondary neuron decussates in caudal medulla, crossing in the internal arcuate fibers
  • becomes medial lemniscus which begins ascending anterior midline but gradually moves away from midline through brainstem
  • synapse in VPL nucleus of thalamus
  • tertiary neuron projects via posterior limb of internal capsule to synapse in S1
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3
Q

Epicritic also called

A

lemniscal pathway

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4
Q

Epicritic afferent fiber type

A

large, rapidly conducting, myelinated fibers:

  • A-beta Ib run from GTO, carry sensation and muscle force info
  • A-beta II run from skin receptors (Pacinian, Ruffini [skin/joint], Meissner’s, Merkel’s), carry sensation
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5
Q

Protopathic carries what?

A
  • pain (fast [Adelta] and slow [C fibers])
  • temperature
  • crude touch
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6
Q

Protopathic runs where?

A
  • into dorsal horn, up/down Lissauer tract, synapse in layer I/V
  • from dorsal horn (V), secondary neuron crosses midline in the anterior white commissure; as they ascend new fibers are added medially (legs lateral, arms medial)
  • ascends spinal cord and brainstem in the anterolateral tract; runs lateral through brainstem but then moves more dorsal while staying lateral when going from medulla to pons to midbrain
  • synapses in VPL of thalamus, with collaterals to the intralaminar (projects diffusely throughout cortex for general arousal) and dorsomedial nuclei (for projects to prefrontal cortex)
  • tertiary neuron projects to S1
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7
Q

Protopathic also called

A

lateral spinothalamic

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8
Q

Protopathic afferent fiber type

A

small, slowly conducting, lightly myelinated or unmyelinated fibers:

  • A-delta (lightly myelinated) run from free nerve endings, carry fast pain/temp
  • C fibers (unmyelinated) run from free nerve endings, carry second pain/temp
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9
Q

Vestibulospinal

A
  • mediates reflex to catch yourself in a fall*
  • falling sensed by vestibular system
  • from vestibular nuclei
  • innervates neck and trunk muscles
  • integrates/coordinates movements of head/trunk based on balance
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10
Q

Reticulospinal

A
  • from reticular formation (in pons/medulla)
  • innervates neck and trunk muscles
  • coordinates movements of head and trunk
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11
Q

Rubrospinal

A
  • from red nucleus

- travels closely with corticospinal tract and participates in control of arm muscles

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12
Q

Colliculospinal/Tectospinal

A
  • turns head/eyes when your attention is caught in the periphery*
  • from superior colliculus
  • to cervical spinal cord to innervate neck muscles
  • coordinates head/neck movements with eye movements and attention
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13
Q

Corticobulbar

A 
motor cortex to brainstem to innervate ipsi/contralateral brainstem motor nuclei
- 3, 4, 5, 6: ipsi and contra
- 7 - upper face: ipsi and contra
  7 - lower face: contra only
- 9, 10, 11, 12: ipsi and contra
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14
Q

Somatotopy of corticospinal and corticobulbar tracts in: cortex, IC, and spinal cord

A
  • cortex: face is lateral, leg/foot is medial
  • internal capsule: corticospinal is posteromedial, corticobulbar is anteromedial
  • spinal cord/LMNs: extremities are lateral, trunk is medial
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15
Q

Pyramidal tract

A

aka corticospinal
- runs from motor cortex (pre-central gyrus)
- descends via corona radiata, posterior limb of internal capsule, then through the crus cerebri in anterior midbrain then start to break up in pons
- 85-90% of fibers decussates at the pyramidal decussation in the lower anterior medulla and form the lateral CS tract
- the remaining 10-15% of fibers descend ipsilaterally and are called the anterior CS tract
- Spinal cord to LMNs:
lateral CS tract –> synapses in anterior horn
anterior CS tract –> crosses midline at level and then synapses on LMN in anterior horn

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16
Q

Dorsal spinocerebellar tract

A

carries unconscious proprioceptive input from periphery to the cerebellum

17
Q

A alpha afferents

A
  • Epicritic information on touch and pressure*
  • (Ia and Ib) mostly carry info from muscles - spindles and GTOs, resp.
  • these synapse in deep dorsal horn layers, as well as directly in ventral horn on alpha motoneurons for monosynaptic reflex
18
Q

A beta afferents

A
  • Epicritic information on touch and pressure*
  • carry cutaneous and joint sensations
  • synapse in deep dorsal horn
19
Q

A delta and C fibers

A
  • Protopathic information on pain and temp*
  • first synapse in Substantia gelatinosa (Rexed layers I and II) for modulation
  • can also synapse first in layer V
  • interneuron can project up/down in Lissauer tract
  • second-order neuron gets input in the ipsilateral dorsal horn, then decussates and ascends in the anterolateral spinothalamic tract
20
Q

Spinoreticular tract

A
  • division of the spinothalamic tract but terminates in the reticular formation in the pons (instead of thalamus)
  • neurons come from all layers of the dorsal horn
  • for general arousal, emotional aspects of pain
21
Q

Spinomesencephalic tract

A
  • division of the spinothalamic tract but terminates in the periaqueductal gray in the midbrain (instead of thalamus)
  • neurons come from layer I and V of the dorsal horn
  • important for activating descending efferent pathways that modulate pain
22
Q

Trigeminal epicritic input

A
  • cell body in trigeminal ganglion
  • synapse in chief/principal sensory nucleus of V
  • some decussate and ascend in ATT; some don’t decussate and ascend in PTT
  • all go to VPM to synapse and then project to lateral S1
23
Q

Trigeminal protopathic input

A
  • cell body in trigeminal ganglion
  • descend in spinal trigeminal tract
  • synapse in spinal trigeminal nucleus
  • decussate
  • ascend in ATT/ventral trigeminal lemniscus
  • synapse in VPM, project to lateral S1
24
Q

Dorsal spinocerebellar tract

A
  • afferents from spindles and GTOs from leg and body
  • afferents ascend via fasciculus gracilis
  • synapse in Clarke’s nucleus
  • project to cerebellum with synapse in inferior cerebellar peduncle
25
Q

Cuneocerebellar tract

A
  • afferents from spindles and GTOs from arm
  • afferents ascend to synapse in accessory cuneate nucleus
  • project to cerebellum with synapse in inferior cerebellar peduncle
26
Q

Ventral spinocerebellar tract

A
  • afferents from GTOs from leg and body
  • afferents synapse in layer 7 of spinal cord
  • decussate in anterior white commissure
  • ascend in lateral funiculus (close to anterolateral tract)
  • synapse again in the superior cerebellar peduncles
  • then some decussate again, the rest don’t before entering cerebellum
27
Q

Rostral spinocerebellar tract

A
  • afferents from GTOs from arm
  • afferents synapse in layer 7 of spinal cord
  • ascends to cerebellum very laterally in spinal cord
  • synapse in inferior cerebellar peduncles then to cerebellum

OS9.1 - Neuro (8 decks)

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