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Neuroscience > Somatosensory Pathway 2 > Flashcards

Somatosensory Pathway 2 Flashcards

1
Q

Nondiscriminative touch, thermal, and nociceptive sensations are conveyed by the?

A

The Anterolateral System (ALS)

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2
Q

The Anterolateral System (ALS) is relayed from?

A
  • body –> thalamus –> somatosensory and limbic cortices
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3
Q

Anterior trigeminothalamic pathway relays from?

A

face/head –> thalamus –> somatosensory and limbic cortices

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4
Q

What symptoms does disruption of ALS cause?

A

Numbness, tingling, & prickling (paresthesia) → to

complete loss anesthesia

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5
Q

Cutaneous Nociceptors and Primary Neurons:

  • All are morphologically ?
  • Fibers enter SC via the lateral division of ?
A
  • free nerve endings

- posterior root entry zone

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6
Q

Central Pathways from the Body:

  • Travel in ?
  • Central target of primary afferents includes laminae ? of posterior horn
A
  • posterolateral fasciculus
    (Lissauer tract)
  • I, II, and V
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7
Q

Carries nondiscriminative tactile, innocuous thermal, and nociceptive
signals

A

Direct Spinothalamic Pathways

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8
Q

Direct Spinothalamic Pathways:

• Ascending branches terminate on 2nd order neurons of the posterior
horn, which project to lateral region of the thalamus

  • Axons cross midline via ?
  • Ascend in the ?, few will ascend in ipsilateral ALS (not clinically relevant)

• Thalamic (3rd order) neurons are located in the VPL (VPI & posterior
group)

• ? terminate on interneurons within gray matter and contribute segmental spinal reflexes

A
  • anterior white commissure
  • contralateral ALS
  • Descending branches
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9
Q

Polysynaptic component that relays noxious and innocuous mechanical and thermal information to reticular formation

A

Indirect Spinothalamic Pathways

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10
Q

Indirect Spinothalamic Pathways:

• Branches of these fibers ascend/descend in the posterolateral
fasciculus

  • Synapse in laminae ? and ? will influence cells in laminae ? to ?
  • Send axons that cross obliquely through AWC (over 1-3 segments) & to
    join contralateral ALS
  • These ? terminate in reticular formation (brainstem)
  • Third-order neurons in RF project to the ?
A
  • II and III
  • V to VIII
  • spinoreticular fibers
  • medial thalamic nuclei
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11
Q

ALS fibers that ascends directly to ventral
posterolateral [VPL] and ventral posterior inferior [VPI] nuclei, and posterior
nuclear group (including VMpo)

A

Spinothalamic fibers

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12
Q

info from SC that ascends to various brainstem nuclei

A

Spinobulbar fibers

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13
Q 
somatosensory info (including nociceptive)
from posterior horns that ascends directly to hypothalamus
A

Spinohypothalamic fibers

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14
Q

may terminate in the midbrain reticular
formation

  • May also transition to form ? targeting deep layers of superior colliculus & anterior pretectum
A

Spinomesencephalic fibers

  • spinotectal fibers
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15
Q

ALS

• Axons from lower levels
(coccygeal, sacral) of the body are found ?

• More rostral levels are added in an ?

A
  • posterolaterally

- anteromedial sequence

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16
Q

Lesions of ALS:

• Blood supply originates from ? & via ?

A
  • arterial vasocorona

- sulcal branches of the anterior spinal artery

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17
Q

Lesions of ALS:

• Occlusion results in patchy loss of nociceptive, thermal, & touch over the ? side of the body
- Begins about two spinal segments below the lesion

• What results in complete loss of these sensation?

A
  • contralateral

- Anterolateral cordotomy

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18
Q

What kind of loss do you get with Hemisection of the Spinal Cord?

A

• CONTRALATERAL loss of nociceptive & thermal sensations over body

  • Begins about two segments below
    level of the lesion (ALS damage)

• IPSILATERAL loss of discriminative tactile, vibratory, and position sense over the body at and below the level of lesion (posterior column damage)

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19
Q

Cystic cavitation of central regions of spinal

gray matter

A

Syringomyelia

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20
Q

Syringomyelia:

• May impinge on ? (contains decussating
ALS fibers

• When located at the ? levels of the spinal cord

  • Produces ? of
    nondiscriminative tactile, nociceptive, &
    thermal sensations
  • Begins several segments below lesion
  • Symptoms present in configuration of a
    cape draped over shoulders & down to
    nipple level
A
  • AWC
  • C4 to C5
  • bilateral loss
21
Q

• Positioned near anterolateral surface,
anterior to spinal trigeminal nucleus

• Remain separated from the PCMLS

A

Medullary ALS Fibers

22
Q

Medullary ALS Fibers:

Vascular lesions/tumors in lower brainstem can affect?

A

discriminative

touch & nociception differentially

23
Q

contralateral loss of discriminative
touch & vibratory sense, but pain/thermal sensation is WNL (one
modality absent but not another)

A

Dissociated sensory loss

related to Medullary ALS Fibers

24
Q

Mixed nerve with sensory and motor
components
- Main sensory nerve for the head
- Innervates the muscles of mastication

A

Trigeminal Nerve

25
Q

Attaches to the brainstem as two adjacent roots (large sensory &
smaller motor) on ventrolateral aspect
of the pons

A

Trigeminal Nerve

26
Q

3 divisions of the Spinal Trigeminal Nucleus?

A
  • pars caudalis, pars oralis, and pars interpolaris
27
Q

Spinal Trigeminal Nucleus:

  • Both nucleus & tract extend caudally to about ? segment
A

3rd cervical

28
Q

Spinal Trigeminal Tract & Nucleus:

• In anatomic orientation, face is ? in spinal trigeminal tract
& nucleus
- Ophthalmic representation is
located ?

  • Mandibular representation is
    located ?
A
  • inverted
  • inferiorly
  • superiorly

(opposite for clinical orientation)

29
Q

CN V Central Pathways:

  • most caudal part, extending from the spinal
    cord (C2, C3) to the obex
A

Pars caudalis

30
Q

CN V Central Pathways:

-most rostral part, extending from the main sensory
nucleus to pontomedullary junction

A

Pars oralis

31
Q

CN V Central Pathways:

  • located in between, in rostral medulla
A

Pars interpolaris

32
Q

Pars Caudalis:

When spinal trigeminal tract is damaged have
characteristic pattern of ?

A

onion-peel sensory

loss

33
Q

Pars Caudalis
• spinal trigeminal tract is damaged:

  • More ? lesion → larger the area surrounding
    the mouth that is spared from sensory loss
  • More ? lesion (into brainstem) → sensory
    loss that starts at back of head & converges on
    mouth
A
  • caudal

- rostral

34
Q

Trigeminal Pathway:

  • Second-order axons from caudal nucleus decussate & ascend in ?
  • Terminates in the ? VPM of thalamus (at periphery)
  • Tertiary axons extend in posterior limb of the ? → primary somatosensory cortex
A
  • anterior trigeminothalamic tract
  • contralateral
  • internal capsule
35
Q

Trigeminal Pathway:

  • Blood supply to trigeminal structures in medulla are via ?
A

PICA & posterior spinal artery

36
Q

Pain fibers project bilaterally to the reticular formation as?

A

trigeminoreticular fibers

37
Q
  • Trigeminal input into the RF facilitates the ascending reticular activating system (ARAS), & plays an important role in?
  • RF is a set of connected nuclei responsible for regulating?
A
  • arousal & alertness

- wakefulness and sleep-wake transitions

38
Q

Extends from the level of entry (pons) to superior
medulla
- Receives tactile information from the central region of the face

A

Pars oralis

39
Q

Extends from superior medulla to obex

- Receives information from the peripheral region of the face

A

Pars interpolaris

40
Q

Heavily involved in functions homologous to somatic functions of the spinal cord

  • Project fibers to the cerebellum (through the inferior cerebellar
    peduncle)
  • Carry tactile information project to the contralateral VPM
A

Pars Oralis and Pars Interpolaris

41
Q

What does Unilateral lesion of the Trigeminal Nerve cause?

A
  • Anesthesia and loss of general sensations in the trigeminal dermatomes
  • Loss of jaw-jerk reflex
  • Atrophy of the muscles of mastication
  • Loss of ipsilateral and consensual corneal reflex
42
Q

What does alternating analgesia of the Trigeminal Nerve cause?

A 
• Brainstem lesions in the upper medulla may destroy the primary fibers in the spinal
trigeminal tract (descending tract of V), & secondary fibers in the spinal lemniscus

• Patients demonstrate ipsilateral hemianalgesia of the face & contralateral
hemianalgesia of the bod

43
Q

What does Alternating trigeminal hemiplegia of the Trigeminal Nerve cause?

A
  • Unilateral destruction of the trigeminal nerve and CST in the pons
  • Ipsilateral trigeminal anesthesia and paralysis, and contralateral spastic hemiplegia
44
Q

What supplies the
territory of anterolateral
system AND spinal trigeminal nucleus/tract?

A

Posterior inferior cerebellar

artery (medulla)

45
Q

Vascular lesions involving Posterior inferior cerebellar artery (medulla) produces what syndrome?

A

lateral
medullary (Wallenberg)
syndrome (posterior inferior cerebellar artery syndrome)

46
Q

What occurs in patients with Lateral Medullary Syndrome?

A

• Contralateral loss of pain (hemianalgesia) and temperature
(hemithermoanesthesia) over the body WITH

• Ipsilateral loss of these modalities over the face

47
Q

In response to a stimulus that touches the cornea, the eyes blink

A

Corneal Reflex

48
Q

Corneal Reflex:
• Afferent limb of originates from ? receptors in the cornea

• Fibers travel on ? & have cell bodies in the trigeminal ganglion →
terminate in ? spinal
trigeminal nucleus

• ? fibers send collaterals ? into the facial motor nucleus (efferent limb) of this reflex

A
  • pain/touch
  • V1
  • ipsilateral
  • Trigeminothalamic
  • bilaterally

Neuroscience (14 decks)

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