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NE Exam 2 > Lecture 9: Somatosensory Pathways Part 1 > Flashcards

Lecture 9: Somatosensory Pathways Part 1 Flashcards

1
Q

What information does the PCML and trigeminothalamic pathway transmit?

A

Discriminative Touch
Pressure
Vibration
Proprioception

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2
Q

What is two point discrimination?

A

Ability to discriminate between two stimuli simultaneously

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3
Q

What areas would have high density of tactile receptors?

A

Digits

Perioral region

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4
Q

What areas would have low density of tactile receptors?

A

Back

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5
Q

Small receptive fields have ____ receptor density.

Large receptive fields have ____ receptor density.

A

Small receptive fields have HIGH receptor density.

Large receptive fields have LOW receptor density.

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6
Q

What type of axons are primary afferent fibers?

A

Sensory

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7
Q

Where do primary afferent fibers have their cell bodies?

A

Dorsal Root Ganglion

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8
Q

In the PCML pathway, where do primary afferent fibers enter the spinal cord?

A

Medial division of posterior root

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9
Q

In the PCML pathway, where do primary afferent fibers travel after entering the spinal cord via the posterior root?

A

Posterior Columns: Fasciculus Gracilis and Cuneatus

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10
Q

Where is Fasciculus Gracilis found (both generally in the SC and in an SC cross section)?

A

Found in whole spinal cord but receives input from sacral Region to T6 (located medially)

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11
Q

Where is Fasciculus Cuneatus found (both generally in the SC and in an SC cross section)?

A

T6 and above (located laterally)

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12
Q

Which fibers are found more medially?

A

Sacral and the more rostral you go, the more lateral those fibers are found

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13
Q

What supplies the posterior columns?

A

Posterior Spinal Artery

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14
Q

If the PCML pathway is affected from a spinal cord lesion, what can happen?

A

Ipsilateral reduction or loss of discriminative, positional, and vibratory tactile sensations
Will happen at and below level of injury

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15
Q

What is sensory ataxia?

A

Loss of muscle tendon reflex and proprioceptive losses from extremities due to lack of sensory input
Can lead to difficulty walking and wide based stance

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16
Q

In the PCML pathway, where are 2nd order neurons found?

A

Gracile and Cuneate Nuclei in the posterior medulla

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17
Q

Where are the gracile and cuneate nuclei receiving their input from?

A

First order neurons (primary afferents) from ipsilateral dorsal root ganglion

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18
Q

What are internal arcuate fibers?

A

After synapsing at the gracile and cuneate nuclei, they are the fibers that cross anteromedially in the medulla

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19
Q

What is medial lemniscus?

A

The new name of the fibers after they cross at the medulla until they terminate

20
Q

In the medial lemniscus, where do the upper and lower extremity fibers now reside after the rotation in the pons?

A

Upper: Medial
Lower: Lateral

21
Q

Where does the medial lemniscus terminate?

A

Ventral Posterolateral Nucleus of the Thalamus

22
Q

What supplies the medial lemniscus?

A

Anterior Spinal Artery

23
Q

What supplies the Ventral Posterolateral Nucleus of the Thalamus?

A

Thalamogeniculate Branches of Posterior Cerebral Artery

24
Q

From the Ventral Posterolateral Nucleus of the Thalamus, where do the third order neurons go to?

A

Primary and Secondary Somatosensory Cortices

25
Q

How do third third order neurons reach the somatosensory cortices?

A

Via Posterior Limb of Internal Capsule

26
Q

What compromises the Primary Somatosensory Cortex (S1)?

A

Postcentral gyrus and Posterior Paracentral Gyrus

27
Q

What are the Brodmann Areas of the Primary Somatosensory Cortex?

A

31, 3b, 1, and 2

28
Q

If there is a lesion to the Middle Cerebral Artery, where would there be tactile loss?

A

Contralateral upper body and face

29
Q

If there is a lesion to the Anterior Cerebral Artery, where would there be tactile loss?

A

Contralateral lower limb

30
Q

What does the secondary somatosensory cortex sense?

A

Inner face

31
Q

Where does secondary somatosensory cortex gets its input from?

A

Ipsilateral SI cortex and Ventral Posterior Inferior Nucleus of the Thalamus

32
Q

What happens if the parietal cortical region is lesioned?

A

Agnosia: cannot recognize own limb

33
Q

What is the role the mesencephalic nucleus?

A

Conveys unconscious proprioceptive afferents and pressure afferents from TMJ, masticatory, and extraocular muscles

34
Q

What is the role the principal/chief sensory nucleus?

A

Discriminative touch and pressure from face

35
Q

What is the role the spinal nucleus?

A

Pain, temperature, and non-discriminative touch from face

36
Q

In the Sensory Trigeminothalamic Pathway, where are primary afferents from?

A

Trigeminal Ganglion

37
Q

In the Sensory Trigeminothalamic Pathway, where are 2nd order neurons found?

A

Principal/Chief Sensory Nucleus

38
Q

What supplies the Principal/Chief Sensory Nucleus?

A

Superior Cerebellar Artery

Long Circumferential branches of Basilar Artery

39
Q

What are the two divisions of the principal/chief sensory nucleus and what do they receive information from?

A

Dorsomedial: Oral Cavity
Ventrolateral: V1, V2, V3

40
Q

How does the dorsomedial division reach the thalamus?

A

Travels ipsilaterally via posterior trigeminothalamic tract to

41
Q

How does the ventrolateral division reach the thalamus?

A

Travels contralaterally via anterior trigeminothalamic tract

42
Q

Where do both anterior and posterior trigeminothalamic tracts synapse at?

A

Ventral Posteromedial Nucleus of the Thalamus

  • Oral Cavity: Medial part of nucleus
  • External Face: Lateral part of nucleus
43
Q

From the Ventral Posteromedial Nucleus of the Thalamus, where do the third order neurons go to?

A

Primary somatosensory nucleus via posterior limb of internal capsule

44
Q

What reflex is initiated when there is a downward tap on the chin?

A

Jaw-Jaw Reflex: Stretching of masseter muscle causes it to contract bilaterally

45
Q

What is the pathway of a jaw-jaw reflex?

A
  1. Innervation of Mesencephalic Trigeminal Neuron
  2. Innervation of masseter muscle spindle
  3. Synapse on trigeminal motor neuron

NE Exam 2 (28 decks)

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