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Yr2 Control - Term 2 and 3 > Ascending Sensory Pathways > Flashcards

Ascending Sensory Pathways Flashcards

1
Q

What does somatosensory mean?

A

Relating to a sensation that can occur anywhere in the body (e.g. pain), rather than localised at one organ (e.g. sight).
-I.e. senses other than 5 senses

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2
Q

What are the 2 groups of somaesthetic modalities?

A
  • Modalities that are essential to survive

- Modalities that increase detail

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3
Q

What sort of modalities are essential to survive?

A

Pain, temperature, some touch & pressure.

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4
Q

What fibres carry modalities that are essential for survival?

A

Thin, unmyelinated fibres.

-relatively slow conduction

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5
Q

What sort of modalities increase detail?

A
  • Discriminative touch (2-point and vibration)

- Proprioception

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6
Q

What fibres carry modalities that increase detail?

A

Large, very myelinated fibres.

-fast conduction

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7
Q

What is proprioception?

A

The body’s ability to sense movements in joints and joint positions.

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8
Q

What is the general mechanism of proprioception?

A

Golgi tendons/muscle spindles sense degree of tension/stretch in muscles&raquo_space; CNS.

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9
Q

What is a pseudounipolar neuron?

A

Sensory neuron in PNS with a single stalk that splits into 2 processes.
(1&raquo_space; periphery, 1&raquo_space; spinal cord)

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10
Q

What is a nucleus?

A

Collection of cell bodies in the CNS.

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11
Q

What is a ganglion?

A

Collection of cell bodies in the PNS.

-e.g. dorsal root ganglion

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12
Q

How many neurons do general sensory pathways consist of?

A

Three.

-1/2/3*

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13
Q

Where do the cell bodies of sensory 1* neurons in the PNS reside?

A

Dorsal root ganglion.

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14
Q

Where do the cell bodies of sensory 1* neurons in the CNS reside?

A

Cranial nerve nuclei.

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15
Q

Where do 1* neurons synapse?

A

In the CNS (spinal cord/brain) on the same side as they entered the cord (ipsilateral).

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16
Q

Which neuron crosses the midline?

A

2* neuron.

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17
Q

Where do 2* neuron cell bodies reside?

A

In ipsilateral grey matter in the CNS.

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18
Q

What happens to 2* neurons once they cross the midline?

A

They ascend to the thalamus.

  • VPL nucleus (from body)
  • VPM nucleus (from face)
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19
Q

Where do 3* cell bodies reside?

A

In the thalamus.

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20
Q

Where do the 3* axons project?

A

3* axons project to the somatosensory area of the post-central gyrus.
-Contralateral 1* neuron origin

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21
Q

What does somatotopic mean?

A

Point-to-point correspondence.

-area of body&raquo_space; specific point on post-central gyrus

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22
Q

Are general sensory pathway somatotopic?

A

Yes.

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23
Q

Is synaptic transmission from 1, 2 and 3* neurons a simple relay? Give 3 examples.

A

No, can be modified by other inputs.

-e.g. diverging circuit, converging circuit, descending pathways

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24
Q

What is a diverging circuit?

A

One pre-synaptic neuron stimulates a response in multiple post-synaptic neurons. Increases the amount of info to CNS, and allows brain signals to travel to various locations of the body.

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25
Q

What is a converging circuit?

A

Several pre-synaptic neurons stimulate one post-synaptic neuron. Focuses information.

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26
Q

What is the general pathway of sensory information to the face?

A

Sensory stimulus&raquo_space; 3 neurons&raquo_space; thalamus (VPL/VPM)&raquo_space; post-central gyrus.

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27
Q

Which arteries in the medial hemisphere supplied by?

A

Anterior cerebral arteries.

28
Q

What are the main ascending and descending fibre tracts? (4)

A
  • Dorsal column
  • Spinothalamic
  • Lateral corticospinal
  • Ventral corticospinal
29
Q

What are the major ascending tracts? (2)

A
  • Dorsal column pathway

- Spinothalamic pathway

30
Q

What information does the spinothalamic pathway carry?

A

Pain, temperature, light touch and pressure.

31
Q

What information does the dorsal column pathway carry?

A

Discriminative tough and proprioception.

plus some simple touch and pressure

32
Q

Which ascending pathway synapses at the level of spinal cord entry and crosses the midline to ascend contralaterally?

A

Spinothalamic pathway.

33
Q

Where does the 1* neuron synapse in the spinothalamic pathway?

A

In the dorsal grey horn (spinal cord).

34
Q

What do 2* neurons of the spinaothalamic pathway cross the midline in?

A

Ventral white commisure.

-ventral to the central canal

35
Q

How do 2* fibres ascend in the spinal cord to the thalamus in the spinothalamic pathway?

A

In the spinothalamic tract on the contralateral side.

-anterolateral spinal cord

36
Q

Which areas of the body (1* neuron origin) travel in which areas of the spinothalamic tract?

A

Medial - arm.
Middle - trunk.
Lateral - leg.

37
Q

What does the spinthalamic tract become at the medulla?

A

Spinal lateral lemniscus.

38
Q

NB. what are the 3 parts of the brainstem?

A
  • Medulla oblongata
  • Pons
  • Midbrain
39
Q

Which part of the thalamus does information from the body in the spinothalamic tract go to?

A

Ventral posterolateral nucleus (VPL).

40
Q

Which part of the thalamus does information from the face in the spinothalamic tract go to?

A

Ventral posteromedial nucleus (VPM).

41
Q

Where does the 2* neuron synapse in the spinothalamic pathway?

A

In the thalamus.

  • VPL for body
  • VPM for face
42
Q

Where does the 3* neuron project to?

A

Post central gyrus.

-1* somatosensory cortex

43
Q

Where is the 1* somatosensory cortex located?

A

In the lateral postcentral gyrus (parietal lobe).

44
Q

What is the function of the 1* somatosensory cortex?

A

Main sensory receptive area for touch.

45
Q

Which ascending pathway ascends in the spinal cord ipsilaterally, and synapses at the level the closed medulla?

A

Dorsal column pathway.

46
Q

What information does the dorsal column pathway carry?

A

Discriminative tough and proprioception.

plus some simple touch and pressure

47
Q

Which part of the spinal cord do 1* neurons of the dorsal column pathway ascend in?

A
  • Gracile fascicles

- Cuneate fascicles

48
Q

Which fascicle is located medially (gracile/cuneate)?

A

Gracile fascicle is medial.

49
Q

Which fascicle is located laterally (gracile/cuneate)?

A

Cuneate fascicle is lateral.

50
Q

What level of the spinal cord does the gracile fascicle run in?

A

Runs entire length of the spinal cord.

51
Q

What level of the spinal cord does the cuneatefascicle run in?

A

Above T6 only.

52
Q

Where does the gracile fascicle take information from?

A

Below T6 and the legs.

53
Q

Where does the cuneate fascicle take information from?

A

Above T6 and the arms.

NB if 2 fascicles are present on either side&raquo_space; must be above T6

54
Q

What do the gracile and cuneate fascicles become the level of the medulla?

A

Gracile and cuneate tubercles.

55
Q

What do the gracile and cuneate tubercle contain, and what happens in them?

A

Contain nuclei.

-where 1* neurons synapse before crossing the midline

56
Q

At what level do 1* neurons synapse in the dorsal column pathwaty?

A

At the level of the closed medulla.

57
Q

What do 2* neurons of the dorsal column pathway cross the midline in?

A

In internal arcuate fibres.

58
Q

What do 2* neurons ascend in after crossing the midline?

A

In the medial lemniscus.

-posterior to the pyramids at closed medulla

59
Q

NB what is a lemniscus?

A

A collection of axons (ribbon/band).

60
Q

Where do the 2* neurons synapse in the dorsal column pathway?

A

In the thalamus.

  • VPL for body
  • VPM for face
61
Q

Where do 3* neurons project to in the dorsal column pathway?

A

Post central gyrus.

-1* somatosensory cortex

62
Q

Which parts of the ascending pathways are somatotopically organised? (4)

A
  • Medial lemniscus
  • Lateral lemniscus
  • Thalamus
  • Post-central gyrus
63
Q

What do fibres travel from the thalamus to the post-central gyrus in?
-dorsal column and spinothalamic pathways

A

The posterior limb of the internal capsule.

64
Q

CASE STUDY.
Wound to lower back&raquo_space; spinal cord lesion:
-loss of proprioception and discriminatory touch over lower right torso and leg
-analgesia and thermoanaesthesia (no pain/temp sensation) over lower left torso and leg

Where is the lesion?

A

Below T6 on right hand side.

  • dorsal column pathway (proprioception and discriminatory touch) = ipsilateral
  • spinothalamic pathway (analgesia and thermoanaesthesia) = contralateral
65
Q

What kind of neuron is a primary neuron of a general sensory pathway?

A

Pseudounipolar.

66
Q

Do all the fibres in the spinothalamic tract decussate at the level of entry to the spinal cord?

A

No, most do but some ascend ipsilaterally in the spinal cord for a few vertebral levels before decussating.
-carry light touch and pressure

Yr2 Control - Term 2 and 3 (17 decks)

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