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Neuro > Somatosensory System II > Flashcards

Somatosensory System II Flashcards

1
Q

Somatosensory sensation from trunk and limbs

A

DC-ML and ALS

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2
Q

Somatosensory sensation from the head

A

Proprioception & fine touch —> principal nucleus V CN
Gross touch, Tª & pain —> V spinal nucleus
Muscle spindles —> mesencephalic nucleus of trigeminal

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3
Q

Trunk and limbs somatosensory information

A

DC-ML
ALS: ant & lat spinothalamic tracts

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4
Q

DC-ML pathw —> relay stations

A

1st —> medulla
2nd —> thalamus
3rd —> cortex

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5
Q

DC - ML conveys

A

Proprioceptive & fine touch perception

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6
Q

DC - ML pathway

A

1º sensory neurons in spinal dorsal root ganglia —> Info to spinal cord - central process courses up along post funiculus of SAME side to medulla (within white matter of spinal cord)

Medulla: 1st relay / synapse —> fibers DECUSSATE = ML -> ascends along brainstem on OPPOSITE side -> neurons reach thalamus.

Thalamus: 2nd relay —> synapse w/ neurons in thalamic nuclei.

The 3rd neuron —> Thalamocortical projections - projects to cerebral cortex (area that deals w/ sensory info, mainly 1ª somatosensory cortex)

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7
Q

1st relay station, in the Medulla (DC -ML) - fibers

A

Thickest type + largest diameter —> Type I & Type II fibers (A-alpha and A-beta)

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8
Q

1st relay station, in the Medulla (DC -ML) - pathway

A

Enter medially to dorsal horn

Ascend through DC (provide some collaterals before ascending, to enable reflexes like stretch one)

Main axons
- travel on = side (Gracile (LL) / Cuneate (UL) fascicles)
- reach 1st site of relay in medulla
- enter corresponding nuclei in medulla (Gracile or Cuneate)
- synapse
- DECUSSATE
- form + continue ascending as medial lemniscus through Pons & Medulla
- reach thalamus

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9
Q

Inferior limb fibers ascend trough … (DC-ML)

A

Gracile fascicle, medial

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10
Q

Superior limb fibers ascend through… (DC-ML)

A

Cuneate fascicle, lateral

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11
Q

After decussating, gracile fascicle fibers from the lower limb end up being

A

Inferior

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12
Q

After decussating, cuneate fascicle fibers from the lower limb end up being

A

Middle-superior

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13
Q

For rostral parts of ML (once its turned horizontally), lower limb fibers are

A

Lateral

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14
Q

For rostral parts of ML (once its turned horizontally), upper limb fibers are

A

Medial

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15
Q

All somatosensory information from the trunk and limbs makes relay (2nd synapse) in

A

Ventral posterolateral nucleus of the thalamus (VPL)

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16
Q

In the thalamus, lower limb fibers are … (DC-ML)

A

More lateral in the VPL

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17
Q

In the thalamus, upper limb fibers are … (DC-ML)

A

More medial in the VPL

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18
Q

The 3rd neuron will ascend from thalamic nucleus through

A

Thalamocortical tracts

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19
Q

Regarding the cortex, lower limb fibres will go to … (DC-ML)

A

Medial aspect of the 1ary somatosensory cortex

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20
Q

Regarding the cortex, upper limb fibres will go to … (DC-ML)

A

Dorsolateral aspect of the 1ary somatosensory
cortex

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21
Q

ALS conveys

A

Gross touch, pain and Tª

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22
Q

ALS pathway

A

Thick A-delta and C fibers enter laterally —> SYNAPSE
in post horn —> DECUSSATE ascending in
contralateral anterolateral column

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23
Q

ALS fibers

A

Type III or A-delta fibers
Type IV or C fibers

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24
Q

1st relay station: spinal cord (ALS)

A

Enter dorsal part of spinal cord + lateral, closer to post horn —> synapse + decussate = ant white commissure.

Ascend via anterolateral funiculus (between lat - ant funiculi) —> some end in different areas of brainstem and others ascend directly to thalamus.

For brainstem, ALS provides collaterals: pain info and gross touch -> connected to different structures of brainstem (integrated at unconscious level for reflexes -> autonomic)

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25
Q

Lesions affecting anterior commissure will be affecting (spinal cord, ALS)

A

Pain, Tª and gross touch from both hemi bodies

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26
Q

Lesion in the spinal cord after the decussation will affect

A

Contralateral hemibody

27
Q

2nd relay station: thalamus (ALS)

A

End at the Ventral posterolateral nucleus (VPL)

28
Q

Lower limb fibers are … (ALS)

A

Lateral

29
Q

Arms and trunk fibers are … (ALS)

A

Medial

30
Q

In thalamus, lower limb fibers synapse … (ALS)

A

More laterally

31
Q

In thalamus, upper limb fibers synapse … (ALS)

A

More medially

32
Q

After synapsing at the VPL, 3rd neurons ascend to the cortex, to the … (ALV)

A

1ary sensory cortex

33
Q

In the cortex, lower limb fibers are … (ALS)

A

Medial

34
Q

In the cortex, upper limb fibers are … (ALS)

A

Dorsolateral

35
Q

Somatosensory inputs from the head are conveyed by

A

Trigeminal nerve

36
Q

Trigemino-thalamic pathways

A

V CN enters brainstem at the level of pons.

1st neuron has its body in trigeminal ganglion.

Central processes extend —> synapse in trigeminal nuclei (2nd neurons).

2nd neuron DECUSSATES, ascends to thalamus —> reaches contralateral thalamus, ending in VPM (post part of the complex) —> somatosensory cortex

37
Q

Trigeminal nerve nuclei in brainstem

A

Principal nucleus
Spinal nucleus
Mesencephalic nucleus

38
Q

Principal nucleus of the V CN location

A

Mid portions of the pons.
Lat to motor nucleus of the V CN.

39
Q

Principal nucleus of V CN receive

A

Type I and Type II neurons (thick): proprioception + fine touch perception

Thinner fibers: proprioception + fine touch from face

40
Q

Principal nucleus of V CN - after fibers arrive..

A

Synapse w/ 2nd neurons in the nucleus
2nd neuron exits the nucleus
Majority of fibers DECUSSATE and course medial to medial lemniscus —> thalamus.
These fibers = Ventral trigeminothalamic tract —> end in Ventral posteromedial nucleus of the thalamus (VPM)

41
Q

Principal nucleus of V CN - exception

A

Fibers from oral cavity end in a specific area of the principal nucleus —> ascend ipsilaterally (JUST THESE) —> end in medial most part of VPM of = side!

These ipsilateral fibers = Dorsal trigeminothalamic tract

42
Q

Fibers from the face ascend … (to principal nucleus of VCN)

A

Ventrally

43
Q

Fibers from oral cavity ascend … (to principal nucleus of VCN)

A

Dorsally

44
Q

Laterally in the VPM (ventral posteromedial nucleus)

A

Skin and mucosa form the face

45
Q

Medial in the VPM (ventral posteromedial nucleus)

A

Info from oral cavity (periodontal ligaments)

46
Q

Spinal nucleus is where

A

Gross touch, pain and Tª inputs from the face mostly reach (Type III + Type IV fibers)

47
Q

Spinal nucleus of V CN - fibers pathway

A

Central processes enter Pons and depending on the
info they convey, they look for the corresponding area of the spinal nucleus —> form the spinal tract.

Synapse —> 2nd neuron DECUSSATES —> incorporate into Ventral trigeminothalamic tract.

(Neurons from spinal + principal nuclei will form part of this tract)

48
Q

Mesencephalic nucleus of V CN contains

A

Cell bodies of Type IA fibers (or A-alpha) from muscle spindles of masticatory muscles

49
Q

Mesencephalic nucleus of V CN - pathway

A

Somas in the midbrain

Mesencephalic nucleus: central process —> thin chain between periaqueductal gray substance - tectum (still 1ary sensory neurons).

Central processes go down = mesencephalic tract —> SYNAPSES in principal trigeminal nucleus!

Collaterals to spinal nucleus and motor nucleus of V (reflexes).

50
Q

Muscle spindles give rise to

A

Stretch reflexes

51
Q

Neurons in mesencephalic nucleus are

A

Afferent arm of the Mandibular reflex

52
Q

Mandibular reflex

A

Afferent fiber = muscle spindle neuron in mesencephalic nucleus

Efferent branch = motor alpha neuron form motor trigeminal nucleus

53
Q

VPL and VPM are

A

sites of relay for all somatosensory information

54
Q

VPL = for

A

somatosensory info from trunk and limbs (both DC-ML and ALS)

55
Q

VPM = for

A

somatosensory info from head.
Inputs from face reach lat, info from oral cavity (teeth) reach med.

56
Q

Medial most part of the VPM receives

A

Taste information

57
Q

VPM projects to

A

Ventrolateral aspects of the 1ary somatosensory cortex (info from the face processed)

58
Q

VPL ends in

A

dorsolateral and medial aspects of the 1ary sensory cortex (limb and trunk somatosensory inputs)

59
Q

1ary somatosensory cortex is in

A

Parietal lobe, in postcentral gyrus, just post to central sulcus.

60
Q

primary somatosensory cortex corresponds to

A

Brodman defined areas 3, 1 and 2

61
Q

Distinction between the three Brodman defined areas is

A

That different modalities end in each area

(All the tracts that have been separately gathering info, end in the = area but separately, w/ distribution)

62
Q

Somatosensory cortices are classified as sensory due to

A

Developed layer 4 → granular cortices

63
Q

Somatosensory cortices (1ary, 2ary and associative)

A

Sensory info —>

1ary sensory cortex

2ary sensory cortices / unimodal association cortices
- associate info from S1
- connected to higher order nuclei in thalamus

Heteromodal association cortices / Higher order association cortices
- integrate different somatosensory modalities of info)
- most common are parietal lobe and prefrontal cortex

Neuro (23 decks)

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