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Neuroendocrine Exam 2 > 10.1 Somatosensory Tracts 1 (Dennis) > Flashcards

10.1 Somatosensory Tracts 1 (Dennis) Flashcards

1
Q

What are the functions of the sensory nuclei of the trigeminal nerve?

A

Principal sensory nucleus (msT)

  • Descriminative Touch and pressure.

Spinal nucleus

  • nondescriminative touch
  • Pain
  • Temperature

Mesencephalic nucleus (mes)

  • Proprioception for chewing/extraocular/TMJ
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2
Q

What are the two divisions of the main sensory nucleus of the trigeminal nerve?

A

The main sensory nucleus has two divisions:

  • Dorsomedial division
    • Afferents just from the oral cavity.
  • Ventrolateral division
    • Afferents from V1, V2, and V3
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3
Q

In the fasciculae gracilis and cuneatus, are the fibers from the upper extremity more lateral or more medial to the fibers from the lower extremity?

A

Upper extremity fibers are more lateral in the PCML system.

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4
Q

Where do the third order neurons of the PCML system travel?

A

VPL-> thalamocortical path->posterior limb of internal capsule->SI

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5
Q

What is the specialization of the outer shell and inner core of the nuclei gracilis and cuneatus?

A

The outer shell of the nuclei gracilis and cuneatus specializes in proprioception.

The inner core specializes in sensation.

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6
Q

What do we call the decussation of the PCML secondary fibers immediately after the synapse of the nucleus gracile/cuneatus?

A

Internal arcuate fibers.

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7
Q

Where would lesions to the middle cerebral artery cause loss of sensation?

Where would lesions to the anterior cerebral artery cause loss of sensation?

A

MCA lesion would cause tactile loss over contralateral upper body and face

ACA lesions would affect contralateral lower limb

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8
Q

What are the three parts of the spinal nucleus of the trigeminal nerve?

A

Pars caudalis,

Pars oralis,

Pars interpolaris

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9
Q

Where do the dorsomedial and ventrolateral fibers of the main sensory nucleus of the trigeminal nerve synapse?

A

On the ventral posteromedial nucleus of the thalamus.

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10
Q

What nucleus in the thalamus does the PCML pathway synapse onto?

A

The ventral posteriolateral nucleus of the thalamus.

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11
Q

What artery supplies the PCML in the spinal cord?

What artery supplies the PCML in the medulla (and up from there)?

A

Spinal cord = posterior spinal artery

Medulla and up = anterior spinal artery

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12
Q

Where do the afferent first order fibers of the PCML system enter the spinal cord?

A

At the medial division of the posterior root.

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13
Q

What symptom is associated with damage to the secondary somatosensory area?

A

Agnosia – the loss of ability to recognize a limb as part of the body.

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14
Q

What artery supplies the ventral posterolateral nucleus?

What would happen if these were occluded?

A

The thalamogeniculate branches of the posterior cerebral artery.

Complete loss of discriminative touch, pressure sensation, and proprioception to the contralateral body.

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15
Q

Where are the cell bodies for first order sensory neurons?

What type of nerves are these?

From what layer are these nerves derived?

A

Dorsal root ganglion.

Pseudounipolar nerves.

Neuroectoderm.

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16
Q

What are the two divisions of the fibers from the main sensory nucleus of the trigeminal nerve?

What are their contents?

A

Dorsomedial division: contiains afferent input from the oral cavity.

Ventrolateral division: contains afferent input from V1, V2, and V3.

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17
Q

What type of information is carried by the VPL pathway?

A

two point discrimination

mechanical sensation (texture, 3d shape, size, etc)

proprioception

vibration

to body!!

18
Q

Where do we find the nuclei gracilis and cuneatus?

A

In the posterior medulla.

19
Q

What is the purpose of the mesencephalic nucleus?

A

Primarily relays proprioceptive information related to chewing.

20
Q

At the level of the pons, are fibers from the nucleus gracilis medial or lateral to the fibers of the nucleus cuneatus?

A

Fibers from the nucleus gracilis are lateral in the pons.

in other spinal levels, the nucleus gracilis is medial

21
Q

Where is the switch over from fibers coming together to form the fasciculus gracilis to becoming the fasciculus cuneatus?

A

T6

above T6 FC-upper ext/upper body

below T6 FG-lower limb/body

22
Q

What are the hallmark traits of the PCML system?

A

fast velovcities

precise somatotopic organization

two point discrimination

23
Q

receptor density gradient vs. receptive field

A

digits and mouth have high density of tactile receptors and other places like the back have low density

small receptive fields have high receptor density while large receptive fields have low density

24
Q

Describe sx of lesions of the fasciculi gracile and cuneatus

A
  • ipsilateral loss of discriminative, postitional, and vibratory sensation at and below level of injury
  • sensory ataxia, loss of tendon reflexes, loss of proprioception from extemities
  • wide base stance (this is common in Tabes dorsalis in neurosyphillis)
25
Q

Describe the Primary Somatosensory Cortex (S1)

A

postcentral gyrus and posterior paracentral gyrus

divided into Brodmann areas (3a, 3b, 1 and 2 from low to high)

supplied by ACA and MCA

26
Q

The secondary somatosensory cortex (SII) is located ____ and receives input from ____

A

inner part of lateral sulcus

ipsilateral SI cortex and VPI of thalamnus

lesion=agnosia

27
Q

Describe the path of the 2nd and 3rd order fibers of the trigeminothalamic tract

A

2nd order fibers have two options:

ventrolateral division projecting contralaterally via anterior trigeminothalamic tract (most) (proprio., disc. touch) or dorsomedial division (fewer) projecting ipsilaterally via posterior trigeminothalamic tract (goes to oral)

these then target the VPM nucleus (oral=medial) and (face=lateral)

these then go to the 3rd order neurons via the posterior limb of the internal capsule to the SI

*crosses over in pons*

28
Q

The mesencephalic nucleus is the only nucleus where?

conveys what?

projects where?

does what reflex?

A

CNS

unconscious proprioception from oral/extraocular muscles

principal sensory nucleus and spinal nucleus

forms circuit for jaw-jerk reflex

29
Q

Describe the jaw jerk reflex

A

downward tap on chin stretches masseter and causes it to contract bilaterally

aff-mesencephalic trigeminal neuron innervating masster spindle

eff-trigeminal motor neuron

enhanced amplitude after UMN injury

30
Q

Main blood supply to trigeminal nuclei (mesencephalic, motor, principal sensory)

A

long circumferential branches of basilar A.

AICA

31
Q

Main blood supply to mesencephalic nucleus and tract

A

long circumferentail branches of basilar A.

Superior cerebellar A.

32
Q

Overview of dorsomedial trigeminal pathway

A

head/neck–>principal sensory nucleus of V (dorsomedial)–>posterior trigeminothalamic tract–>ipsilateral VPM–>S1

33
Q

OVerview of ventrolateral trigeminal pathway

A

head/neck–>principal sensory nucleus of V (ventrolateral)–>anterior trigeminothalamic tract–>contralateral VPM–>SI

34
Q

PCMLS pathway-cuneatus pathway overview

A

UE–>FC–>Nucleus cuneatus–>medial lemniscus–>VPL–>SI

35
Q

PCMLS pathway Nucleus Gracilis overview

A

LE–>FG–>Nucleus gracilis–>medial lemniscus–>VPL–>SI

36
Q

Effects of damage to primary afferents

A

ipsilateral

no change in strength

decreased/lost reflexes

decreased/loss sensation

37
Q

effects of damage to 2nd order neurons/brainstem

A

contralateral

no change in strength or reflexes

loss of sensation

38
Q

effects of damage to SI

A

contralateral

no change in strength or reflexes

loss of sensation

39
Q

Lesion at R. posterior columns at L1 causes what deficits?

Lesion of R. fasciculus cuneatus at C3 produces what impairments?

A

loss of light touch, vibration, proprioception of the right leg

only fasciculus gracilis exsits below T6

same as above but for right arm and trunk

40
Q

Complete transection of posterior columns in the cervical region would cause what deficits?

A

damage to fasciuli cuneatus and gracilis

absence of light touch, vibration, prioprioception bilaterally from neck down

41
Q

What artery supplies the medial lemniscus?

A

ASA until it reaches the cuadal medulla

42
Q

REmeber the stupid question you asked about VPM vs. VPL…well now you won’t forget that…

A

VPL is for the body

VPM is for the face

Neuroendocrine Exam 2 (25 decks)

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